Introduction: Step-by-step Guidance to Build a Drone From Scratch Using Ardupilot APM Navio2 Flight Controller

About: Hi! I am an Electrical Engineer. I live and work in Malaysia! Nice to Meet You!

Ardupilot is a widely used open source unmanned vehicle autopilot software that is capable of performing many functions. Documentations and various sources have provided us with the basic knowledge of the setups and use each separate component of a drone but none has provided a detailed guide on how to put them together to build the drone’s hardware with guided steps of component setup and assembly from scratch, together with all necessary configuration and setups.

This article is written to combine all scattered information into one piece, to provide a step-by-step guidance from head to tail of how to build and assemble a quadcopter from scratch and how to perform all setup configurations required using the Navio2 Ardupilot flight controller. Other flight controllers from APM or others can also partly rely on this guide.

In each of the steps shown below, there are pictures or tables that helps you to understand more. Note that the pictures or tables illustrates the details of texts within the involved step itself only. You will need to click on the image to see in full size. A PDF version of the entire guide is attached below, which is much clearer and less confusing in showing the details regarding tables and photos. There are a total of 16 sections and all the steps below are all derived and organised from the 16 sections of the PDF file attached. There are sub-sections for each sections grouped as steps. Again, if you find it confusing or troublesome, simply download the attached PDF file that is ready-made.

If you would still prefer to adhere to the steps below, the following guides linking the step numbers to section names may be useful:

Intro Introduction

Step 1-15 1.0 Full Component List

Step 16-19 2.0 Thrust-to-weight ratio

Step 20-21 3.0 Navio2 hardware setup

Step 22-37 4.0 Drone Hardware Setups

Step 38-42 5.0 Flashing OS into microSd card

Step 43-49 6.0 Raspberry Pi Wi-Fi network configuration setting

Step 50-53 7.0 SSH Raspberry Pi on your laptop using PuTTY

Step 54-57 8.0 Setting up Ardupilot

Step 58-66 9.0 Connecting to your Ground Control Station (GCS)

Step 67-79 10.0 Flight calibration on Mission Planner (MP)

Step 80-86 11.0 Change the flight mode on mission planner with respect to radio transmitter

Step 87 12.0 Installing a turn-off switch to the RPi3

Step 88-95 13.0 Running an autonomous mission

Step 96-99 14.0 Manual Flight control

Step 100-106 15.0 Data Flash Log Analysis

Step 107-115 16.0 Object Avoidance Implementation

First let us select and purchase all the components that are required. The components can be purchased from different sites or sources but a basic requirement guide for all components will be provided as shown. A summarised list of the required components and the links to purchase each of the components are as shown in the PDF file named Drone BOM List (All pricing are converted into Malaysia Ringgit MYR or RM). Those components are the low-cost, high quality components that I have searched through the internet. Most of the components are from Chinese companies. I have tested them I believe they have similar qualities with their western counterparts but at much lower prices. However, you need to be extra careful when you want to purchase components from Alibaba because strangely cheap components from untrusted sites may have compromised qualities.

Otherwise, I also have included Affiliate Links into each component for your reference to buy from Alibaba or Amazon. Those affiliate links were not included in the PDF files attached.

To purchase a slightly more complete guide backed with some researches based on technical papers:

Step 1: 1.0 Full Component List

Make your BOM list of components online from links like in the PDF file named ‘drone BOM list’ attached below. Those are the links where I purchase my components. Components from other sites can be used but bear in mind that the rule of thumb of buying components from online is to avoid buying components that are too cheap. The more you pay, the better the quality you will get.

Before your flight, consider buying a reliable ready-made drone to hone your flying skill first:

Affiliate Links: Amazon (Common rugged drone for practising)

(Note: e.g. Amazon may pay me commission if you purchase through the Affiliate link)

Step 2: 1.1 Navio2 Emlid Flight Controller

The main function of the Flight Controller is to provide control for the Electronic Speed Controller (ESC) to direct the rpm of motors based on inputs from the transmitter.

One of the advantages of using the Navio2 flight controller is because it has most of the components built-in so we do not need to buy them separately and integrate them by ourselves. The components that comes together in the Navio2 flight controller include

1. Dual Inertial Measurement Unit (IMU)

2. Barometers measure altitude accurate to 10 cm of resolution.

3. GNSS receiver tracks satellites from all over the world.

4. Compass or magnetometer determines the direction of heading

5. Extension ports allocate for additional sensors and radio telemetry.

6. Radio Communication co-processors accept PPM or SBUS inputs from receiver, and output 14 PWM channels for motors and servos at the servo rails

The link to the website to purchase Navio2 Flight Controller is as follows

Remember to also buy the dampener ball to connect the Navio2 board to its 3D printed holder (You will also need to 3D print the holder or purchase it online. Refer to Step 3>

Step 3: 1.2 Raspberry Pi3 Model B

Raspberry Pi is a micro-computer at the size of an average credit card for data processing. With the General Purpose Input Output (GPIO) pins, the Raspberry Pi has high processing capability to run functions like flying a drone. Of the 40 pins of extended GPIOs, Navio2 has utilised 37 of them for flight control, leaving only 3 free GPIOs for additional components, that is GPIO 17 (Pin 11), GPIO18 (Pin 12), and GPIO 26 (Pin 37).

Amazon Affiliate Link for Raspberry Pi3 Model B:

Step 4: 1.3 Airframe

The airframe makes up the body of the quadcopter with arms, landing gears, mounts, power distribution boards and blade protectors. The X frame is chosen because of good symmetry, simpler design, more flexibility and suitable for abrupt tilting. The selected frame size has a frame of 485 mm. The arrangement of the airframe size has to match with those of the batteries, propellers, as well as motors, as shown in the table above.

To tighten the screws connecting the different parts of the airframe, you will need Alan keys of suitable sizes. Assemble the airframe tightly using suitable sizes of Alan keys (Vibrations may cause the screws to fall apart), according to guides provided by your supplier.

The airframe should come together with a Power Distribution Board (PDB) where we solder all wiring on its terminals to connect the battery to the Flight Controller (through Power Module wire), to the ESCs and Motors (through the ESCs wiring).

You will need a connector to connect between the PDB and the power module, whereby one end of the connector is to be soldered onto the PDB. For the other end, you need to make sure its connector head is compatible with your Power Module wire. The power module splits the current from the battery to the PDB and a small part to the Flight Controller. Therefore, its terminal connector also has to be compatible with that of the battery. Referring to the image above, XT-60 connectors are to be connected to its XT-60 counterparts, whereas T-connectors has to be connected to its T-connector counterpart.

Amazon Affiliate Link to S500 drone air frame:

Amazon Affiliate Link to purchase Connector from Power Distribution Board to Power Module:

Step 5: 1.4 Motors 2216/950KV

The selection of the motor type depends on the size of the propellers or drone. A larger propeller should be powered by rotors of lower rpm because of the higher air resistance. A 950 KV motor means the motor has a 950 rpm of speed for each volt it is connected across. 2216 specifies the motor size. The following data (also shown in the image for the Component - 1.2 Airframe) can act as a general guide but the most suitable motor sizes can be those suggested by the manufacturer/dealer.

Frame Size---Motor size---Motor KV/Speed--Prop size(In)








It is recommended to buy a few spares of the motor caps (as shown in the third photo). A motor cap covers and holds the propellers in place, and can falls off easily if the cap is not tightened enough (It is highly recommended to tighten it fully using a spanner). It can be troublesome to look for fallen motor caps especially in grassy areas. If the motor cap falls off, it usually will be somewhere near to your quadcopter. Look for it around and not far from the the drone.

Try to buy motors of different colours to differentiate the direction of rotations. 2 motors will be rotated clockwise and 2 motors anti-clockwise, depending on how you will connect it to the 3-phase ESC output, which will be discussed in the Hardware setup section later on.

If you are buying a motor for drone, it should come with connectors to your ESCs. Contact your dealer to check if the package includes the connector. Some suppliers has ready-made (3 phase) bullet connectors attached to the motor while some include them in the package for the buyers to solder on themselves.

Amazon Affiliate Link to purchase BLDC Motors:

Step 6: 1.5 Electronic Speed Controller (ESC)

An Electronic Speed Controller (ESC) draws current to drive the rotor based on output from the Flight Controller’s servo rail. The ESC is graded with the maximum amount of current that it allows to pass through. Therefore, the selection of ESC is supposed to be such that the ESC rating is 1.2 to 1.5 times of the maximum rating of the rotor. For example, since the selected motor draws a maximum of 15 Amps (look for the maximum current draw from the motor datasheet or current rating specifications provided by the supplier) 20 Amps of ESC for each rotor would suffice without causing any overheating or burnouts. According to the equation below,

ESC Rating/Maximum Motor Rating = 20/15 = 1.3333

It is best that the above equation yields values within the range of 1.2 to 1.5. And since the maximum current draw is rare, 20 A of ESC will suffice so long the ESC exceeds that of the motor current rating.

It is recommended to use ESCs without a Battery Eliminator Circuit (BEC). The navio2 flight controller can provide power supply to the ESC circuit and the receiver through the servo rail. BECs are therefore not required. However, if your ESC comes with BEC, it can still be used. Follow through the steps in the 'Drone Hardware Setups' Section to insulate the terminal.

Amazon Affiliate Link to Purchase ESC: (With BEC)

AliExpress Affiliate Link to purchase ESC:

Step 7: 1.6 Propellers

The propeller has to be selected based on the intended reliability and then sized according to the motor speed (Refer to the image Guide in Component 1.2). Carbon fibre propellers are of higher quality but may not necessarily worth the cost. After all, carbon fibre propellers will also break under similar circumstances of impact. A softer propellers, on the other hand, may even be more flexible and less 'fragile'. They are also less stiffer in resisting air, thus may be better at reducing possibilities of motor heating in large drones. With relatively large airframe of 485 mm (580 mm including the propeller protectors), the rotor speed selected is lower at 950 KV, and the propeller size is correspondingly larger at 12 inches or 30.48 cm. Propellers are balanced on a propeller balancer using additional electrical tapes to make sure both blades are of equal mass. This minimises vibrations that could arise from unbalanced propellers. Mount the propellers on the propeller balancer, turn off your fan, and then tape the end of a lighter propeller blade until balance. You can shift the tape across the length of the blade to find the spot for perfect balancing. While balancing, always make sure that the propeller movement is not restricted. It should be able to swing freely on the propeller balancer even with the slightest breeze. The grip of the propeller balancer must not be too tight.

AliExpress Affiliate Link to purchase Propellers: (Search your specific size of propellers and try to purchase in bulk. Consider buying more for spare. You certainly will break some propellers before you can get your flight stable)

Amazon Affiliate Link to purchase Propellers:

Step 8: 1.7 GNSS Receiver With Antenna

A Global Navigational Satellite System (GNSS) receiver is the built-in GPS (and other satellites’) receiver in Navio2. It requires an antenna that is raised high up away from the flight controller to avoid magnetic interferences generated from the components leading to GPS glitches or inaccuracy of satellite signal reception. A GPS stand is where the antenna is being mounted to, while the other end connects to the flight controller’s GNSS receiver through a micro coaxial (MCX) connector. The micro co-axial connector will come with the GPS antenna set purchased, but the GPS stand has to be purchased separately, or 3D-printed online. It is recommended to have it purchased online because those are designed to be bent when you want to place your drone upside-down during calibration (as shown in the photographs on the right).

Make sure you purchase the right connector for your APM flight controller in which case Navio2 uses an MCX connector:

AliExpress Affiliate Link to purchase GPS antenna holder/mount: Product - Quadrocopter Kit F450 GPS Folding Antenna Mount Bracket Naza tarot 650 680 diy drone kit Rc FPV gps antenna mount

Step 9: 1.8 Transmitter

A high grade transmitter is what required to enable good control of a flying vehicle. This is crucial because otherwise, fatal injuries could be the result following an impaired communication. The Radiolink AT10II series is by far the most advanced transmitter the company has developed, offering hybrid of Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS) radio communication protocol with the receiver, which then communicates with the flight controller via Serial Bus (SBUS) single communication cable. The transmitter can be powered with a small 2200 mAh Li-Po battery provided by the supplier to save battery replacement cost. The transmitter will also come with the receiver in a pair.

AliExpress Affiliate Link to purchase AT10 Radiolink Transmitter C/W receiver: Product - F07627 RadioLink AT10 2.4GHz 10CH Remote Control System 10 Channel Transmitter Receiver R10D for RC Helicopter

Amazon Affiliate Link to purchase AT10 Radiolink Transmitter C/W receiver:

Step 10: 1.9 Receiver

It is highly recommended to use a transceiver pair whose receiver can communicate with Navio2 through SBUS communication protocol. The R12DS receiver I used receives signals from the transmitter and then relay the signal to the flight controller via SBUS communication protocol. SBUS is a new single-wire communication protocol (saves a lot of messy wirings) that is supported by Navio2. One signal wire transmit all radio values of all 12 channels from the receiver (which is in turn transmitted wirelessly from the transmitter) to the flight controller. Navio2 has built-in decoder to decode SBUS RC input values before passing them to the Ardupilot. To connect the receiver to the flight controller, you will need three female-to-female jumpers to connect the signal, positive and negative terminals of the SBUS line from the receiver to the respective signal, positive and negative terminals in the servo rail of the Navio2 flight controller. Use shorter jumpers for better tidiness.

Step 11: 1.10 MicroSD Card

Similar to a computer that requires Hard Disk Drive (HDD) or the latest Solid State Drive (SSD) as storage, the Raspberry Pi uses a microSD card in which the operating system (Raspbian) is being installed. It contains crucial files that store system data such as connection IP addresses, file directories with codings for different features, etc.

AliExpress Affiliate Link to purchase 32GB microSD Sandisk:

Amazon Affiliate Link to purchase 32GB microSD Sandisk:

Step 12: 1.11 Lithium-Polymer (Li-Po) Battery

Lithium battery has one of the highest power-to-weight ratio, making it one of the best choices for powering UAVs. However, Li-Po battery has to be taken care of thoroughly and have its voltage monitored so that each cell stays at least 3V (3.4V to be safe) before it is being recharged.

The Li-Po battery used is a 5200 mAh battery with 25 C rating. To determine if the discharge limit, C is sufficient for the motors used, the maximum discharge current is calculated from.

I_max = C×Ah = 25×5.2 = 130A

This selection is in line with the ESC and battery size, with each ESC rating being 20 A, and a maximum of 80 A (for quadcopter with 4 motors) will be drawn from the battery at a time. Occasions where full throttle are applied are rare and therefore 130 A from a 25 C battery is more than enough.

Li-Po battery size selection has to be made by taking into account the size of the copter for optimum flying duration. If a large drone is powered by relatively smaller sized battery, the flight time will be limited. If a small drone is powered by large batteries out of the optimum range, the battery drains even faster due to the extra weight allocated. The selection of Li-Po battery are best to be as according to the table to achieve maximum available flight time.

You will also have to purchase a wire with suitable that is soldered on the power distribution board to connect between the board and the power module. A T-type connector battery is used. If this type of connector is selected, the Li-Po charger and the power module’s type T connector head should also be selected accordingly. A professional Li-Po charger is recommended because it can monitor the charging voltage and current flow throughout the charging to avoid overcharging. It can also trigger alarms when fault occurs.

Important Note! Before purchase, Make sure to check that the connector can match the connector type of your APM wire and power module. If you are using a T-type connector, all the mentioned components have to have T-type connector. If you want to use an XT60 connector, all the mentioned components have to have XT60 connector. If in doubt, ask your dealer for clarification of the connection type before you purchase.

AliExpress Affiliate Link to purchase LiPo:

Amazon Affiliate Link to purchase LiPo:

AliExpress Affiliate Link to purchase LiPo Charger Professional:

Amazon Affiliate Link to purchase Li-Po Charger Professional:

Step 13: 1.12 Low-voltage Alarm

To protect the Li-Po battery from possibilities of over-discharging, a BB alarm – a loud warning alarm when battery voltage of any cells of the Li-Po dropped below set values – is in place to monitor the battery voltage from time to time. If the battery is allowed to discharge under 3 V per cell, it can be permanently damaged and never be able to recharge back again.

AliExpress Affiliate Link to purchase Low-Voltage BB Alarm:

Amazon Affiliate Link to Purchase Low-Voltage Alarm:

Step 14: 1.13 Power Module

Because the same Li-Po battery supplies both the Raspberry Pi and the motors, a power module controls the voltage across the two according to their optimal requirements. A power module splits the battery current to the power distribution board (to the ESCs) and the power port in the navio2 flight controller. The power module should be carefully selected such that the connector matches that of the battery. A power module with the T-connector head is used if the battery purchased also has a T-connector.

Important Note! Again, before purchase, make sure you check the connector match that of the battery and Power distribution board (PDB).

AliExpress Affiliate Link to purchase Power Module:

Amazon Affiliate Link for power Module:

Step 15: 1.14 Telemetry

A radio telemetry consists of a Universal Serial Bus (USB) ground module to be connected to the Ground Control Station (GCS) which is your laptop, and a Universal Asynchronous Receiver-Transmitter (UART) air module to be connected to the navio2 flight controller. The GCS’s purpose is to plan flight path and monitor flight data. If the UART port’s serial lines have to be used for other purposes such as for obstacle avoidance, or the GPIO 17 of the UART port is used for installation of turn-off switch, the Air Module of the telemetry can be interchanged with that of the Ground Module, with the Ground Module’s USB head connected to the RPi3. The Air Module’s UART requires an additional USB-TTL CP2012 converter to communicate with the GCS, or computer through the Silicon Labs CP210X USB-UART Bridge driver (can be downloaded online). The Amazon Affiliate Link to purchase CP2012 converter (optional):

Amazon Affiliate Link to Purchase Telemetry Module:

AliExpress Affiliate Link to purchase MicroHeader pin for Navio2: Product - CUAV U-BLOX NEO-M8N HIGH PRECISION GPS with two 6pins +4pins DF13 1.25 plugs for Navio2 autopilot

Amazon Affiliate Link to purchase MicroHeader pin for Navio2:

Step 16: 1.15 FPVs and Camera

A Good Camera and Gimbal will enable you to take awesome FPV in flight.

Considering to buy a good camera and gimbal only after you have successfully stabilised your drone.

Amazon Affiliate Link to purchase 3-Axis Gimbal/ Camera Holder (optional):

Camera Holder:

Camera: (Resolution will be proportionate to price)

Step 17: 2.0 Thrust-to-weight Ratio

The calculation of thrust-to-weight ratio of a quadcopter is essential to make sure the quadcopter can take off and fly stably with desired payloads.

Step 18: Calculating the “unladen” Weight of the Quadcopter

The total unladen mass of the quadcopter without any payloads is around 1.336 kg as shown in the table above.

Step 19: Formula for Calculating Generated Thrust

For the drone to be able to take off, the thrust that the rotors produce in total has to exceed that value, or better, twice of that.

Total thrust=2×Total Weight of quadcopter

Step 20: Calculating Thrust to Weight Ratio

The thrust of each motor can also be obtained directly from the motor datasheet. As shown in the above table the equivalent mass of the thrust given is 1110 g for a maximum of 18 A current drawn to each of the rotor. From here, the total equivalent mass of the thrust can be calculated by simply multiplying the thrust by 4 rotors, giving m=4×1.11=4.44 kg. The thrust to power ratio decreases as the power rises faster at higher throttle, with minimum of 5.55 g/W at the highest throttle.

The thrust to weight ratio of the quadcopter without any payloads ratio

=(equivalent mass of thrust)/(flight mass of quadcopter)



Step 21: 3.0 Navio2 Hardware Setup

The first step was to set up RPi3 for Ardupilot. The Navio2 shield was stacked onto the RPi3 and screws were in place to bind the two securely. Navio2 together with the RPi3 would act as the FC of the quadcopter built. Meanwhile, a 3D model holder through which the FC will be secured onto the quadcopter’s airframe was printed. Two parts of the holder were bonded together through 8 shock-absorbing balls. The link provided for the full component list in the PDF file “Drone BOM list” also included these balls.

The link to the documented Navio2 hardware setup is as follows:

Link of Holder parts to 3D-print



Step 22: To Insert the Shock-absorbing Balls to Hold the 2 Printed Holder Parts Together

To insert the shock-absorbing balls to hold the 2 printed holder parts together, do not be too gentle to the balls or it will take you forever to complete the task. Note that these balls are made to be flexible and stretchable. Utilise thin tools like a small Allen key to push the tips of a ball so that they get stuck at the necks into the holes between the 2 printed parts, which have been correctly oriented as shown in the figure above. Repeat for another 7 balls, 2 at each corner. Then, attach the back of your Raspberry Pi onto the upper surface of the printed holder (the one with the larger surface area) using the screws provided.

Amazon Affiliate Link to purchase the dampener ball:

AliExpress Affiliate Link to purchase the dampener ball: Product - 4pcs Universal Anti Vibration Ball Dampening Rubber Balls Shock Absorber for Quadcopter 4-axis Camera Gimbal GoPro Hero Drone

Step 23: 4.0 Drone Hardware Setups

After the previous step is done, leave the Raspberry Pi (stacked with the Navio2 flight controller) with the holder and then proceed with setting up the airframe.

You can try assemble your airframe first if you would love to try out, but you will have to disassemble it for soldering purposes after your motors and ESCs arrive.

Your airframe should consist of a power distribution board. Find the surface of the board that has circular copper terminals marked with positive and negative signs that are meant for soldering of your components. Use a multimeter’s connectivity test to test that all the positive terminals are connected, so do all the negative terminals. I use the soldered surface to be facing up, so I need to make sure that when I solder the cables, they will not obstruct any screw openings connected to the top central cross arm connector. Find appropriate positive and ground terminals on the power distribution board to solder your power module and all 4 of your ESCs to each corners of the power distribution board. All 4 ESCs and motors are the same and can be connected to anywhere so you need not worry which of them to be connected to which corner. Solder the red cables to the positive terminals on the board and the black wires to the negative terminals on the board. The central cable(s) (usually) is the signal cable to be connected to the navio2 flight controller.

Make sure the positive and negative terminals do not short and test the connectivity again after the solder. Secure the connection to the board with more solders in place and test the connection by slightly pulling the cables. Upon completion, the power distribution board should look like a board with hanging threads connecting securely, 4 ESCs and 1 power module. Each of these components is connecetd by 2 wires – red for positive and black for negative.

Step 24: 4.1

Then, assemble the top central cross arm connector with the quadcopter arms using suitably sized Allen keys, and then connect the combined structure with the power distribution board. Adjust the wirings of the ESCs so that they will not obstruct the connection points, if you decided to have the soldered surface facing upward (less possibility of short circuiting with other wirings but needs to diassemble the airframe for resoldering, which can be extremely rare). Now, mount the holder containing the Raspberry Pi 3 and Navio2 onto the central cross arm connector using thick double-sided tapes.

Step 25: 4.2

Mount the motor on the end of each of the quadcopter’s arm together with the propeller protector (optional), with the 3-phase wires facing inward parallel to each quadcopter’s arm. Secure them tightly in place using the provided screws.

Step 26: 4.3

Then, if the motors do not have readily soldered bullet connectors, solder the bullet connector to the end of each of the 3-phase wires of the motors. To do this, use a thin head plier to secure the bullet head connector (may be very hot during soldering), then melt solders into the cylindrical opening. Before the solder hardens, push the wire from the motor into the bullet head connector.

Step 27: 4.4

Hold for a few seconds for the solder to harden completely before you move. Try apply force to test the strength of connection. Loose connections may cause motor failure in the mid flight leading to crashes. If the supplier provided the heat-shrink tubes for insulation, cut a sufficient amount of the tube and lay it over the exposed metal part (with solder connected) under the bullet head, and then apply heat from your soldering gun or a lighter to shrink and have it covered. Otherwise, use an electrical insulation tape.

Step 28: 4.5

Next, secure the each ESC on the top (or bottom) surface of each arm of the quadcopter using cable ties. Then, for now, randomly connect the bullet head connector (may be other types of connectors) of the 3-phase wires of the Brushless DC motors to the 3 outputs of the ESCs by applying a decent amount of strength. The three-phase quasi AC input to the BLDC motor will magnetise coils in the excitable coils in the stator alternatedly such that they repel the permanent magnets (rotor) to turn. The sequence of the 3-phase input to the motor will determine the direction of the rotation of motor. To make sure that the ESCs output a correct sequence of AC current to turn the motor in required directions, you will need to test it out later on.

Step 29: 4.6

When you have your quadcopter armed for the first time (after you have performed all steps that follows), with all propellers removed, you need to make sure that the direction of motor rotation for each motor is as follows. If any of the motor(s) do not rotate in the direction as required, simply interchange any 2 wires that you have randomly connected from the motor (which has wrong direction of rotation) to its powering ESC. Use your finger to feel all motors rotating in the correction direction as in

1. Front right – Anti-clockwise

2. Rear left – Anti-clockwise

3. Front left – Clockwise

4. Rear right – Clockwise

Step 30: 4.7

But that is only one of the last steps you would do before which there are still many to be done. Keep this section toward the end (you will be reminded about this once again after that) and proceed with the following.

Before that, you will need to connect the ESC to the servo rails of the flight controller as shown in the figure above. Refer to the Emlid documentation in the link:

You should now have your ESCs positive and negative inputs soldered onto the Power Distribution board, the central signal cable should be those to connect to the servo rail. Now, the connection of each ESC must be specific. Looking from the left of the servo rail, the leftmost column is the SBUS communication lines (we will deal with it later). The second column, third, forth and fifth column, is meant for the first, second, third and forth ESCs respectively. Please connect them according to the diagram provided by Emlid above.

Step 31: 4.8

Let’s name the central wire of our ESC as the signal wires. The signal wires consist of the actual signal wire, the BEC wire and the ground wire.

The signal wire (central of ESC) consists of 2 wires (for ESCs without BEC) and 3 wires (for ESCs with BEC). If your ESC is without a BEC, it will not have a central BEC wire. The central of the signal wires is empty. If your ESC has a BEC, the BEC wire is usually ‘the centre of the centre’. It is usually the central wire of your 3 signal wires, which is located in the centre of an ESC input.

If your ESC has a Battery Eliminator Circuit (BEC), connect only the BEC wire of your first ESC (can be any other ESCs as long as only one), as shown in the diagram above, on the left, as the orange wire extending from the first ESC. For other ESCs the BEC cable is cut off and insulated (don’t cut wrong- only “the centre of the centre”). This means that only one of your ESC’s central wire (BEC wire) of the central signal wires is connected to the servo rail. The other BEC wires from the other 3 ESCs are removed. This leaves only the first ESC with 3 signal wires (with BEC wire, actual signal wire and ground wire) and the rest of the ESCs with 2 signal wires (with the actual signal wire and ground wire). We know that usually the “central of the central” is the BEC wire, but to differentiate between the actual signal wire and the ground wire, you have to test it out. Again, do this toward the end after you arm your quadcopter. If your motors don’t work as according to the transmitters command (you can hear the change in speed), you have had it connected wrongly. As a rule of thumb, more often than not, the black or dark coloured wire is the ground wire. On the servo rail side, the signal, positive and negative terminals are clearly labelled as the top, middle and bottom row, respectively. The middle (positive) row is where the remaining one BEC wire (if you have one) should connect to, while the actual signal wire should be connected to the first row (of the respective column) marked with the square-wave signal icon. Lastly, the ground wires should be connected to the respective columns in the last row of the servo rail.

If your ESCs do not have a BEC, you will not need to remove or add anything.

Step 32: 4.9

To connect the receiver to the flight controller, you will need three female-to-female jumpers to connect the signal, positive and negative terminals of the SBUS line from the receiver to the respective signal, positive and negative terminals in the servo rail of the Navio2 flight controller. The first or the leftmost column labelled as ‘PPM/SB’ provides the signal, positive and negative terminal for the SBUS communication on the first, second and third line respectively. Use shorter jumpers (for better tidiness) to connect those to their counterparts in the receiver. Secure the receiver with a cable tie.

Step 33: 4.10

After the connection of the ESCs, motors, power module and receiver with the airframe, we are left with the telemetry module, GPS antenna and the battery. The telemetry module comes in a pair – one air module and another ground module. The air module usually comes with a UART micro-header pin connection to be connected to the navio2’s UART port as shown below, whereas the ground module comes with USB connector to connect to your PC.

Step 34: 4.11

(Skip the following section if you are connecting it the normal way) Nonetheless, you can interchange the air and ground module by connecting the ground module (with USB connector) to the Raspberry Pi, and the air module (with UART connector) to your PC. The latter will require an additional USB-TTL CP2102 converter in order that the air module can be connected to the COM port of your PC. The connection of the air module to the converter required soldering, and is as shown in the figure below.

The label on the USB-TTL converter is clear and correct, but on the air module the label within the cover may not be accurate. Maintain the micro-header pin on the telemetry air module side, and cut off the micro-header pin connecting to the UART port. Judging from their connection to the UART port of Navio2, we can know exactly which of the wires are TX, RX, 5V and GND. The port label can be found underneath the Navio2 board or as shown below. The wire that connects to RX on the UART port leads to TX terminal on the air module, while the wire that connects to TX on the UART port leads to RX terminal on the air module. Based on the similar working principle, TX terminal on the air module should be soldered to a jumper connecting to RX of the USB-TTL converter, and vice versa.

Step 35: 4.12

With the 5V and Ground pins connected, the LEDs on the air module will start to blink, signifying the complete circuit in powering up the air module. Make sure that the RX pin of the converter was connected to the TX of the telemetry air module, while the TX pin of the converter was connected to the RX of the air module. Completed connection will show solid light for LED when both the air and ground module are communicating with one another, but that did not imply the telemetry can work in terms of transmitting data for GCS. To achieve this, minor settings have to be done over the RPi3 by logging into the microcomputer’s OS.

From the “etc/default/arducopter” file, the connection configuration was updated to allow this. Details of this is shown in the later steps when you will go into setting up in the section “Connecting to your Ground Control Station (GCS)”.

Step 36: 4.13

A GPS stand is where the antenna is being mounted to, while the other end connects to the flight controller’s GNSS receiver through a micro coaxial (MCX) connector.

Step 37: 4.14

The battery is tied securely under the battery holder using the connecting tie/strip for battery and connected to the Power Module as shown below. One of the outputs of the power module should now been soldered to the power distribution board. The other output, a 6-pin micro-header branches out from the power module, is now connected to the power port of your navio2 flight controller as shown in the diagram above.

Step 38: 4.15

With the battery connected, you will be powering up your Raspberry Pi, Navio2, receiver, and your telemetry. Navio2 will have blinking LEDs whose colours will determine the different conditions of the flight controller. The telemetry module has blinking LED that turns solid when connection is established with its ground counterparts. The receiver should also have LEDs indicative of its supply to the power.

The assembled quadcopter is as shown below. Remember to tie all loose components securely using a cable tie. Then, after you have done with all the hardware setups, you will need to perform a series of software setups, network configurations and flight calibrations before you can set it for its maiden flight.

Step 39: 5.0 Flashing OS Into MicroSd Card

A microSD card which will be used as the storage for the micro-computer, RPi3, has to have the Raspbian Operating system (OS) installed. Choose a suitable size of 16GB or 32GB. Visit the Navio2 developer’s documentation at and download the OS image to your computer. Remember where you store the file because this zipped file downloaded will be “flashed” to your microSD card later on.

Step 40: 5.1

Then, we need a software to flash the downloaded OS into your microSD card. Visit to download and install Etcher. Etcher file is extracted and run on your PC.

Step 41: 5.2

After we get Etcher running, the OS image in the archive file selected is ‘flashed’ into the microSD card. It was found that this process may not be compatible with some PCs, which required other PCs to be used instead.

Plug in your new or newly formatted microSD card to your PC using a suitable card reader or a microUSB adapter. Usually Etcher will automatically select the microSD card as the device to flash. Otherwise change the device to your microSD card before selecting the OS image.

Step 42: 5.3

Select the OS image zip file from where you had it downloaded. Then click flash after it is illuminated!

Step 43: 5.4

This is all required to flash the OS image to your microSD card. The OS image by Ardupilot is a simple one without fancy GUI, and is simple to use. Note that your microSD card has now been partitioned for use of the Navio2 Flight Controller. If you wish to format it (if somehow it corrupts after flashing or after several times of boots), remember to delete the partitions after your formatting. Softwares such as AOMEI partition manager can be used for this purpose.

After the “flash”, your microSD card can now be inserted into your Raspberry Pi3, and then begin network configuration settings, followed by secure shell (SSH) your Raspberry Pi to your laptop using PuTTY.

Step 44: 6.0 Raspberry Pi Wi-Fi Network Configuration Setting

To secure shell your Raspberry Pi to your laptop, you need to connect both your Raspberry Pi and your laptop to the same LAN network – be it through wireless (Wi-Fi), or with cable (Ethernet) connection.

Let’s start with connecting your Raspberry Pi to the internet. It is easier if you are using LAN (or Ethernet) cable. Connect both the RPi and your laptop to the same LAN cable port, and this requires you to have a LAN cable splitter. Split the LAN port to 2 LAN cables. One connect to your laptop and the other to your RPi. Just like on your PC, if you are connecting to the internet using the Ethernet cable, you would not need to perform WPA network configuration (security) on your Raspberry Pi micro-computer so you can skip the step below.

Step 45: 6.1

Otherwise, if you do not have a splitter or if you are not using a LAN cable port, then follow through the wireless configuration step below, just like you would set up connection of your PC to wireless networks – it is only slightly more complicated than how you would normally connect your daily devices to Wi-Fi.

Please note that this network configuration setting is just to connect Raspberry Pi to Wi-Fi network so that it shares with your PC the same network you would connect your PC to. It is different from the network configuration that you will perform for Ground Control Station (GCS) communication via a telemetry module, which will be discussed later on.

As aforementioned, if you are using the Ethernet cable, you can skip the following step and directly go to “SSH Raspberry Pi on laptop”.

Otherwise, network configuration setting is required. Because this step is to enable SSH Raspberry Pi onto your laptop, before that can be done, you can only login Raspberry Pi using an external HDMI monitor and a keyboard. Only for the first time of connection setup (unless you prefer not to use SSH on your laptop but always use a monitor instead), connect your Raspberry Pi to a HDMI monitor or use a HDMI-to-VGA converter to connect to a VGA monitor.

Step 46: 6.2

Power up the Raspberry Pi either by connecting a microUSB charge cable, or by connecting it to the Li-Po battery through the power module. Note that if you are using the Li-Po battery, always attach a BB alarm to monitor the battery voltage to avoid the irrepairable damage if the battery voltage falls below 3 V per cell.

Step 47: 6.3

Then, by looking at the monitor screen, login to the OS by entering the default username and password. The default username is ‘pi’ and the password is ‘raspberry’. The password may not show up but anyways hit enter for each command entered.

Step 48: 6.4

The moment when you login to the OS, you will be greeted with the page as follows

Step 49: 6.5

Copy and paste the command:

sudo nano /boot/wpa_supplicant.conf

and hit enter to go to the file to configure Wi-Fi setting. Password and username of the network over which both the RPi3 and your laptop (with PuTTY) would connect to, is entered as shown. Fill your network name between the “ ” as in “NETWORK NAME” for ssid line and the password of your Wi-Fi network for psk line. If your local network is not password-protected, just leave the psk’s “” empty. These are nothing but the network name and password that you would normally enter to connect your devices to the Wi-Fi. To move the green text insertion cursor, use the arrow keys.

Step 50: 6.6

After that, press “Ctrl+X” to quit and hit key “Y” followed by “Enter” to save what you have editted on the network configuration file. Reboot the ardupilot by typing the command sudo reboot.

If you do not have a monitor or a keyboard, the whole editing process can also be done by editing the text file named wpa_supplicant.conf in the microSD card. To do this, just remove the micro SD card from your Raspberry Pi, plug it into your laptop or PC, and then look for the text file to edit the ssid and psk setting just as you would edit it using the monitor. This time, right-click the file and open with suitable softwares such as WordPad. Save the txt file after editting.

Then, if you are on the monitor display, reboot your Raspberry Pi by typing the command sudo reboot. After device reboot, your Raspberry Pi will then be able to automatically connect to your set Wi-Fi network when it is booted (though it may take some time for the connections). The connection of both your Raspberry Pi and your laptop to the same LAN (either Wi-Fi or Ethernet) is necessary for SSH connection in the following step.

Note: Using mobile or PC hotspot is also the same as using ordinary Wi-Fi. You can monitor from your phone or computer the devices that are connected to your network. If it cannot connect you may restart the RPi3 or recheck the network configuration name and password you have edited in your text file (note that they are case-sensitive and there should not be additional spacing when there is actually none), and wait until it connects (both navio and your PC) and is shown.

Step 51: 7.0 SSH Raspberry Pi on Your Laptop Using PuTTY

PuTTY is one of the network terminal emulator software that enables login to Raspberry Pi using your laptop. It is fine if you do not wish to SSH your Raspberry Pi with your laptop, but this will require you to connect your Raspberry Pi to a monitor and keyboard every time you want to make a configuration settings, such as setting up the Ardupilot, or setting up GCS communication. If that is the case, you don’t even have to perform the Wi-Fi configuration setting and do not need any internet connection. Just directly proceed to “setting up Ardupilot” through the monitor instead of through PuTTY.

Install PuTTY from the link below and follow through all the installation steps. Then search in your PC for PuTTY desktop app and run it.

Link to PuTTY download:

Step 52: 7.1

To connect with PuTTY, type in the configuration “navio.local” as the IP address and enter (or verify) the default port 22 as shown in the figure. Restart PuTTY and try it for several times if it prompts error that local host does not exist. If the condition persists, try disconnect supply to your Raspberry Pi and then reconnect it, i.e. to reboot your Raspberry Pi.

Step 53: 7.2

Repeat the action until PuTTY is started and you are prompted with a warning message from PuTTY. Allow connection by hitting “Yes”. Then, after entering the default “pi” as username and “raspberry” as password, you will be greeted with the same interface you would find by connecting your Raspberry Pi directly to a monitor, but this time is an SSH to your laptop.

If the error “Local host does not exist” persists, it means that you didn’t manage to connect both your laptop and your Raspberry Pi to the same and working network. Try using your mobile hotspot to see if both your laptop and Raspberry Pi (default name of device is navio) are in the list of connected device. If the navio device is not connected, check back to your network configuration setting.

Step 54: 7.3

The entire setup steps can be referred from the official navio documentation:

Step 55: 8.0 Setting Up Ardupilot

If you have powered your Raspberry Pi from Li-Po battery through the Power Module that also powers your ESCs, the ESC will beeps continuously until you have done calibrating your hardware. If you think the beeping sound is annoying, use a microUSB cable to power up the board instead. However, it is not recommended so in the following step because using a microUSB cable will add physical difficulties to the calibration process. Switch to battery connection during the flight calibration steps will ease things out.

Step 56: 8.1

Once the connection was established, entering the default ‘pi’ and ‘raspberry’ username and password will bring forward the same simple interface as shown below. As mentioned, you can lead to this interface either through SSH it on your laptop (where you have to connect both your laptop and RPi to the same LAN) or directly through a monitor.

Step 57: 8.2

In order to set up Ardupilot, the vehicle type, version and board had to be selected through the command “sudo emlidtool ardupilot”.

Use right-click (not Ctrl-C and Ctrl-V) if you want to copy and paste, and hit enter to run the command. The interface will show as below. Follow through the selection of your vehicle type – copter, version of Ardupilot, frame – Arducopter, whether you want Ardupilot to start on boot – enable, start the Arducopter and Apply.

Step 58: 8.3

Then, hit ‘q’ to exit. To check if the ardupilot will be started on boot of the Raspberry Pi, the command: "systemctl is-enabled arducopter" is entered.

The change in vehicle setting required reloading and restarting of the vehicle through the commands, one after another:

sudo systemctl stop arducopter

sudo systemctl daemon-reload

sudo systemctl start arducopter

Or less preferably,

sudo reboot

to directly reboot the arducopter

Step 59: 9.0 Connecting to Your Ground Control Station (GCS)

A Ground Control station is your laptop with a software such as Mission Planner used to monitor the flight in real-time.

You can connect your quadcopter with your Ground Control Station (GCS) using LAN connection (udp connection), just as you would do to set up SSH communication. Udp connection is useful when you want to connect your drone to the GCS for simple tasks such as pre-flight checking, post-flight analysis or retrieving flight data. However, it is recommended that to monitor a flight, a telemetry module pair is used because they are more reliable (do not rely on network connectivity strength), and are easier to connect.

For both udp and telemetry connection, a one-time configuration setting is required for the GCS communication. Type the command to configure telemetry network communication setting:

sudo nano /etc/default/arducopter

If the GCS is going to be connected to the Arducopter through udp, i.e. LAN connection, the IP address of the network, followed by the default udp baud rate, 14550 is entered.

Step 60: 9.1

The network IP address was obtained from network and sharing centre shown in the figure. Take for example this case, we will replace

TELEM1=“-A udp:” with

TELEM1=“-A udp:”

Step 61: 9.2

To open the network connection details in network and sharing centre, go to your control panel and press “view network status and task”

Step 62: 9.3

From the network and sharing centre, select the common LAN that you have had both your Raspberry Pi and your laptop connected to. The network address is taken from the IPV4 address shown above.

Step 63: 9.4

Now if the GCS is going to be connected through a pair of telemetry module, the second line with ‘TELEM2’ was updated. Simply uncomment the line by removing the # symbol in the beginning of the line

TELEM2=“-C /dev/ttyAMA0”

If a USB telemetry (usually a ground module) is used, the third line with ‘TELEM3’ was added. This time replace the “AMA” in the line with “USB” as

TELEM3=“-D /dev/ttyUSB0”

By specifying all entered ‘TELEM1’ to ‘TELEM3’ as your options, any types of connections as mentioned can be established without the need of a reconfiguration in this interface.

Step 64: 9.5

Again, press ctrl-X to leave and ‘Y’ followed by enter to save the changes. Then, reboot your Raspberry Pi through ‘sudo reboot’.

The GCS software used was Mission Planner by Michael Oborne which supports a variety of functions as discussed through easy-to-use interfaces. Download the latest version of Mission Planner from

Step 65: 9.6

If you are using a common LAN for GCS-navio2 communication, select on the top right corner (after you editted the telemetry network configuration address) UDP connection and hit ‘connect’. The baud rate will automatically show, and parameters will be loaded soon. Changes in the values of flight data on the bottom left in Mission Planner will a signify successful connection. If mavlink connection takes too long – after the 30-second counting down – consider restarting your Raspberry Pi, through sudo reboot on PuTTY, or directly unplug and reconnect supply to the Raspberry Pi. Note that it will never connect if your IP address of your network have changed but you have not updated the telemetry network configuration in the above step. Check out the IPV4 address at your network and sharing centre!

Step 66: 9.7

If you are connecting using a telemetry module pair, plug in the air module to the UART port on navio2 and the ground module to your laptop through USB. Wait until the LEDs on both modules stop flashing (i.e. emitting a solid light), go to Initial setup > Optional hardware > Sik Radio on Mission Planner. To do this you will not have to establish udp or any connections before that. Then, press the button “Load setting” and wait as the parameters in the blank spaces are automatically loaded. Save the setting after process is complete. Then go to the other tab and come back to see if the paramteres are still there. If this fails, try to reboot the RPi and attempt several times.

Please note that all hardware connections are shown in the “drone hardware setup” section.

Step 67: 9.8

Then, change the connection to COM4 (the baud rate will also be automatically loaded), and then hit ‘connect’. Telemetry connection usually takes longer time to load parameters but should also show responses within seconds. Again, retry again after rebooting the RPi if this step fails.

Step 68: 10.0 Flight Calibration on Mission Planner (MP)

If we connect the power of the Raspberry Pi through the Power Module from the battery, instead of the micro-USB cable, the esc will beep continuously signifying the setup procedure is yet to complete and the esc does not recognise the flight controller. Only after all calibrations are done, the esc beeping will stop.

Flight calibration is a crucial and compulsory step to complete before the quadcopter can be armed for a flight. To proceed we first connect the Mission Planner GCS to the drone from the previous step, through udp connection, or through a pair of telemetry module (recommended).

It is not necessary to follow through the steps in the setup wizard, that is designed to guide new users through the calibration procedures. The calibration steps are as follows:

Step 69: 10.1

1. Go to Initial Setup tab > Mandatory Hardware > Frame type

Step 70: 10.2

2. The quadcopter airframe type – X-frame – is selected.

Step 71: 10.3

3. Perform accelerometer calibration. Simply place the drone on flat level and then hit “Calibrate Accel”.

Step 72: 10.4

4. The quadcopter is then placed still on a flat surface for level calibration. Different orientations of tilting, as instructed: on level, on its right, on its left, nose up, nose down and on its back, is calibrated. Press the button after each position is properly adjusted. As mentioned, this calibration process is much simpler done when your RPi is connected wirelessly to the GCS through a telemetry and has power supplied through a battery, instead of using LAN cable or power from MicroUSB cable because otherwise movements of the quadcopter will be restricted by the cables.

This step overrides the current state of the quadcopter as level and in different positions, and can be done everytime you see from the attitude indicator (as above) that the quadcopter is not leveled properly.

Note: Telemetry’s connection requires a one-time configuration through Sik Radio connection in optional hardware in the Initial Setup tab, by loading the settings after both the air and ground modules’ LED are in green, solid emitted state.

Step 73: 10.5

5. Magnetometer or compass calibration is required for the accuracy of the quadcopter’s headings, and is performed by moving the quadcopter to cover all directions of the 3-axis planes. To start this, simply hit the start button as shown in the figure below. Calibration will begin collecting required sensor data and the progress of the calibration of the selected compass is shown in the green progress bar.

Step 74: 10.5.1

To calibrate the compass, turn the drone’s top toward you and move it in circle like how you would steer a car to exceed one cycle. Then repeat the actions with the drone’s top facing away from you. Then, rotate the drone on its level then rotate again with it upside down. The video demonstration by Ardupilot on magnetometer calibration is as:

Step 75: 10.5.2

By the end the progress bar should have reached its end and a message to tell completion and prompt restart will be shown.

There are 2 built-in compasses in the navio2 flight controller. If both compass 1 and 2 are used (checked). They both have to be calibrated. If any of the compasses keeps reload (the green progress bar keeps restart again after it progresses to the end repeatedly) when being calibrated, uncheck that problematic compass, i.e. use only compass 1 if compass 2’s progress keeps reloading and use compass 2 if compass 1’s progress keeps reload.

Don’t use the setup wizard if there is problem recurring in the magnetometer calibration. After the calibration is complete, press Ctrl+F to open ‘temps’ and reboot pixhawk as shown.

Step 76: 10.5.3

After rebooting, in order to see the newly calibrated compass offset value, click to go to any other tabs and then back to the compass calibration tab. The offset values are preferably less than 150 for all directions to be considered successful (values are shown in green). If the values are more than 150 (in yellow or in red), redo the calibration. Offsets value that are too high may cause the quadcopter to fail the pre-arm check list.

If several attempts of recalibration turns out similar results, and have ruled out interference of surrounding metal objects, uncheck the compass from the pre-arm check list if you are restricted from arming your quadcopter due to “compass offset too high” after all the calibrations are completed. This is done by going to the Configuring tab > Standard Params > click the ‘Find’ button and search for arm checks. Uncheck ‘All’ and then individually reselect all but compass and write (save) the parameters. Sometimes the failure to arm a quadcopter due to compass offset disappears even after you re-check compass as a component of the pre-arm check requirement.

Step 77: 10.6

6. Radio calibration was carried out to let the Flight controller (FC) know the range of PWM that each channel of radio is sent from the transmitter to the receiver before the FC can translate them into flight control actions. To begin with the calibration, hit the button “Calibrate Radio”. Then, move the left and right sticks on your trnsmitter in all directions while checking that each of them is responding to the right channel as shown below. The left stick controls the yaw (left and right) and throttle (up and down), while the right stick controls roll (left and right) and pitch (up and down). Bring each stick to their 2 extreme ends to get the full range of their PWM value recorded. As the stick is pushed to its extremes, and the red markers that specify the range of radio PWM will expand to the side. If the stick does not respond to the right channel as discussed, modification on the transmitter has to be made, but the transmitter usually would only allow modification on channels other than the first 4, which are fixed for

a. Channel 1: Roll

b. Channel 2: Pitch

c. Channel 3: Throttle

d. Channel 4: Yaw

Note: Please make sure that the transmitter vehicle setting is copter and not other types of vehicles.

Step 78: 10.6.1

If the direction of the response of any radio channel is inverted, reverse the channel signal either through setting on the transmitter or the Mission Planner. For example, if the pitch is shown to be positive in the radio configuration when you push the right stick up, that radio channel can be reversed. After that, all available channels have their radio calibrated by throwing each switch into different directions.

Motor and ESC calibration is performed for better power delivery and motor rotation.

Step 79: 10.7

7. To perform ESC calibration, hit the calibrate ESC button. With the transmitter throttle stick (left) fully pushed up, start your flight controller. Then, after a while, pull the throttle down. The ESC calibration will complete after the long beeping sound stops. If the beeping persists forever, give up the calibration and restart your quadcopter normally with your throttle at minimum. Some ESC calibration will be performed every time they are first connected to the power supply, and is marked by long beeping sounds with the FC LED blinking in read and blue.

After all calibration the beeping sound is gone. If not then the calibration steps may not be complete. Follow through all the wizard just to make sure you covered all the mandatory calibration and setups. Check also if the selected frame type is correct.

Step 80: 10.8

8. Failsafe

It is recommended to set failsafe for the quadcopter to land at low board voltage (unless the board voltage measurement by the FC is not accurate. It is easier and more convenient to use a BB alarm instead. The BB alarm is connected to the Li-Po battery to trigger an alarm whenever the battery voltage drops below a specified limit. The battery voltage below which the alarm is triggered can be set easily through a simple button push that can be found on the BB alarm. It is safe to set it at 3.2-3.4V where when either one of the cells drops below the threshold, you will be alarmed to land your quadcopter.

Radio communication is a crucial component whose failure can cause your quadcopter to be gone forever. Do not use components that can have interference with the radio channel frequency and always check the transmitter voltage and functionality. Safeguard your quadcopter by setting a failsafe for the radio communication by which the quadcopter will Return to Launch (RTL) whenever the radio communication is lost.

The quadcopter can only be armed after all the safety pre-arm checks are completed, which also includes all of the above flight calibration steps.

Step 81: 11.0 Change the Flight Mode on Mission Planner With Respect to Radio Transmitter Channel

As aforementioned, the primary channels (channel 1 to 4) are fixed for the specific type of vehicle selected. The Auxiliary channel on the other hand, can be altered according to our needs. Different transmitters have different methods of setting for the auxiliary channel. Each channel is controlled by a switch on the transmitter. All we need to do is to change the channel’s switch to the specific switch that we want to use to control the specific channel.

Step 82: 11.1

The radio channel setting on your radio transmitter has to be collaborated with the setting on the Mission Planning, and the actual mode that your quadcopter holds to will be as shown in the Mission Planner (not as shown in your Radio transmitter).

To go to the flight mode setting on Mission Planner, connect your GCS to your quadcopter (through udp or telemetry), then go to Configuring > Flight Modes. The flight mode setting in the Mission Planner uses fixed and default channel 5 from your radio. Our aim here is we want to utilise most out of the 6 flight modes switching offered by Mission Planner across the PWM range in channel 5.

Therefore, on your radio transmitter, change the auxiliary channel, Channel 5, to be controlled by a suitable 3-way switch (if you have one). Throw your switch to different positions to test which flight modes that were being engaged at different positions. My 3-way switch at channel 5 engages Flight Mode 1 (when switch position is at Bottom), Flight Mode 4 (when switch position is Mid) and Flight Mode 6 (when switch position is at top). Now change on Mission Planner the by selecting from the drop-down list the modes that we want the quadcopter to engage, i.e. for my case, selecting the modes for flight modes 1, 4 and 6.

Now try to look at the current mode shown to see the changes as you throw your switch across different positions. In my case, for example, the current mode will change from stabilise (bottom) to Altitude Hold (Mid) and Loiter (Top).

Need not worry if your radio transmitter only has 2-way switches. Use the 2 Flight Modes for the mode you think is most important for you. I would suggest Stabilise (the basic one), and Altitude Hold (Important if you are not pro at controlling throttle).

Step 83: 11.2

Landing a quadcopter is equally challenging and you may want to include that as well. I would suggest Land mode to be set from a separate channel so you can leave channel 5 alone for other modes. Simply go to Configuring > Extended Tuning for the mode settings for other channels

Step 84: 11.3

Again, match the setting on your radio transmitter with that on Mission Planner. For example, we first made sure that we set channel 8 to be controlled by a switch (2-way) that we want to use to Land the quadcopter, and then on the Mission Planner, I set channel 8 Opt as Land. Land will be a prioritised mode over all others. This means that if my channel 5 is set as stabilise (say with switch C at bottom), and my channel 8 is set to land (say with switch F on), the quadcopter will go for Land. Always note that the actual mode that the quadcopter engages is shown in the Current Mode shown in Configuration > Flight Modes. From there, always test out different switching of the switches you have set to see if the quadcopter really engage the modes that you desire at all times. As shown in the above diagram, there are 2 more channels from channel 6 and channel 7 where you can use to engage other desired flight modes.

The PWM value of the channel at a particular switch position is shown below the flight mode. It is not recommended to use a knob you are confident because it is hard to gauge the position and the accurate PWM output.

Some radio transmitter allow logic control of switches to control a single channel. This means that 2 switches can be used to control, say channel 5 for more outputs. An example is shown above just for better illustration. This setting can be done on your radio transmitter (if it has this feature) under logic switch which may be different for every transmitter. Spend some time to look through how to perform the setting.

Step 85: 11.4

However, it is not recommended to use logic switch unless you are confident because it might easily cause confusion due to the complexity of switching and can be dangerous at times of panic. To be on the safe side, always use a single 3-way switch and make clear labels on your radio transmitters for the different modes that the different switches will engage. This helps you to be able to respond immediately to emergency cases such as land the quadcopter or disengage a failing mode, than having to figure out which switch to control.

Step 86: 11.5

Above shows the summary of my switch setting as an example for your reference based on the figure on MP (extended tuning) above. The 3 fundamental modes that you may consider setting are Land, Stabilise and Altitude hold.

Step 87: 11.6

Understanding different important flight modes

After the flight mode is set on both your transmitter and your Mission Planner (connected to your drone), you will not require connection to the MP anymore to start the flight, unless you want to monitor your flight. However, make sure you are clear of the modes you are switching into!

Step 88: 12.0 Installing a Turn-off Switch to the RPi3

To turn off the Arducopter, a sudo halt command is required. Similar to a PC, no proper shutting down of devices may corrupt the storage in the long run. Therefore, a switch is installed and the program for the switch operation to turn the device off is being executed on start of the RPi. The switch installation details were being discussed in the hardware component setup section.

The Raspberry Pi starts booting as soon as it receives power supply from the battery. However, there is slightly more trouble when it comes to shutting it down appropriately.

We all know that appropriate shutdowns of the Raspberry Pi microcomputer can be as important as shutting down your PCs appropriately. The shutting down can only be executed after logging into Raspberry Pi, either through proper connections with keyboard or mouse and monitor, or secure shell (SSH) to laptop via PuTTY. Forced shutting down by unplugging the supply may result in SD card corruption in the long run.

Therefore, one of the free GPIOs of the Raspberry Pi – that is not used up by the Navio2 Flight controller – is used to install a turn-off switch for the Raspberry Pi. Only 3 free GPIOs can be used, that is GPIO 17 (Pin 11), GPIO18 (Pin 12), and GPIO 26 (Pin 37). The idea is to write a program that runs on boot in the Raspberry Pi, that whenever GPIO 17 (Pin 11), for example, is shorted to the ground (through a momentary push button switch), the Raspberry Pi will run the command to shut itself down automatically.

To add a turn-off button to the Raspberry Pi, simply follow through the steps in the following link by ETA Prime. It is very straightforward and easy for everyone.

The RetroPie text file can be downloaded from!ppdynJjK!eclxScK_XLy0UmSQeyTK5WyzE5QfmQu0DKZp0WPX9Hc

The contents of the RetroPie text file can be opened with notepad or WordPad, and the commands in the text file are copied one after another, into the pi@navio command interface as shown below

Step 89: 13.0 Running an Autonomous Mission

Please refer to manual flight first if this is the first time you arm your quadcopter.

To test out, first find a wide and empty open field with little obstructions or trees. Carry with you your laptop (Mission Planner), your drone, and all necessary equipment (such as transmitter, spare propellers, spanner for tightening the motor cap if needed, cable ties if needed, etc.) to the empty field. Connect your telemetry ground and air module to your laptop and to the flight controller respectively. Making sure the telemetry connection has been configured as in the section “Connecting to ground control station”, press ‘Connect’ on the top right corner after both the ground and air module has the same solid LED lights (not flashing).

On Mission Planner, go to the Flight Mode tab. Use a mouse to easier navigate through the map. The mouse scroll wheel can be used to zoom in and out of the map, and then use the left-click to drag the map to interactively navigate to any directions. A pop-out dialogue box will ask if you want to set the current coordinate of your drone as the Home location (the point for your drone to take-off). Press ‘Yes’ to do so. With this the quadcopter icon (your drone’s location) on the map will then merge with the ‘H’ icon (Home location) on the map.

With the GPS antenna properly connected to the MCX connector on the Flight Controller (see component setup), the Google map will load automatically the map where your drone is currently at. Note that the home button (‘H’ icon) is loaded as your current drone’s location (quadcopter icon), i.e. the ‘H’ icon must be coinciding with the quadcopter icon. Otherwise, press ‘Home location’ as shown above to do so.

Step 90: 13.1

Next, on the map, perform path planning or mission planning by clicking on points (WP) where you want your drone to follow through as shown below, one WP after another.

Step 91: 13.2

During the path planning, a WayPoint table is automatically generated. The WP table contains the coordinates of location of each of the selected WP and the commands we want the drone to execute at specific WPs. Move your cursor to the line that separates between the map and your table and pull down to enlarge the map with respect to the table.

Step 92: 13.3

To enable the drone to carry out a complete mission, add a WP above the first WP and change the command for the new first WP to be ‘TakeOff’. To add a WP, click on the row below which you want to insert the WP in sequence, and then press ‘Add below’. WP will be added below the row, and press the arrow UP or DOWN to exchange the sequence of the WP. Move the ‘TakeOff’ WP to the top. Then, add below the last WP another new WP and set the new last WP command to be ‘Land’. An example of the WP table is as shown above.

To delete a WP, click ‘X’ and the entire row will be deleted.

Step 93: 13.4

Make sure that your drone will not hit any objects such as trees, poles and etc. that arise near the path planned by avoiding drawing any WP near to them altogether. Set the desired altitude to a suitable value. It is advisable that the autonomous flight has a ground clearance of at least 5 metres. Set it higher to overcome trees, lampposts and other objects. Make sure also that the flight path is complete and there is no WPs that is out of the zone. Be very careful in this because sometimes WPs that are not desired will appear in between and that is shown by yellow lines extending to other locations, Make sure to delete the wrong WPs before any actions are done.

Step 94: 13.5

On the action panel as shown above, there are 4 actions that are important, which are Save, Load, Read and Write. Any WP tables generated on Mission Planner can be saved to your PC as a text file (WP file) so that it can be loaded to the Mission Planner whenever you want to run the same mission. To load a saved WP file, press the Load button and direct to where you have saved your WP file and open it. The WP table will be loaded to your Mission Planner. Double check if the loaded mission is really the mission you intend to run. Then, press the Write button to save the WP table on Mission Planner. After that, press ‘Read’ to send the WP file to the Flight Controller so that the drone will follow through the path. This requires the drone to be connected with the GCS through a telemetry module. After the ‘Read’, Mission Planner will ask again if you want to set the Home location (Launch location) to be at the current loaded drone coordinate. Press ‘No’ to maintain the WP file. Perform the read for several times to make sure your drone is told what to do.

Step 95: 13.6

When ‘Read’ is complete, arm your drone through your transmitter by pushing the left throttle stick (at zero throttle) fully to the right and hold. Your drone should now be placed as mentioned such that the loaded coordinates coincide with the Home Location (press the Home Location button to do so if they are at different locations on the map). Your drone will not arm in autonomous mode or land mode. Switch to stabilise mode first before you arm. For details on the switching between different flight modes, please refer to the section “change the flight mode on the Mission Planner”. Immediately after your drone is armed, engage the autonomous mode, and then give a gentle slight push to the throttle to initiate autonomous mode. The drone will take off automatically to the selected altitude and then begin moving to the first and subsequent WPs.

The speed across which your drone will fly across the WPs can be set from the Full Parameter list by searching for and editing the WPNAV_SPEED parameter. It is easier done on the Configuring tab > Extended Tuning as shown below. The Speed 400.000 means your drone is set to move horizontally at a speed of 4 metre per second. If you are not confident of your GPS accuracy, set the speed to be less than 3 metre per second.

The Landing speed is equally important. Land speed can be set in the full parameter list by searching and editing the LAND_SPEED parameter. The landing speed is the vertical final touch down speed when your drone is about to touch the ground. This value can be best set to be as low as 10 cm/s. The vertical descend speed (before final touch down) of your drone is set from WPNAV_SPEED_DN in the full parameter list. If you are not confident, or if you have barometer sensing errors, set the descend speed to be as low as 10 cm/s as well. Again, this can be easier set on the extended tuning tab, where ‘Speed Dn’ in the figure shown below means the quadcopter will descend at a speed of 1.5 metre/s before reducing to its final touch down speed at your set LAND_SPEED. Remember to hit the ‘Write Params’ button to save any changes.

Step 96: 13.7

To disengage the autonomous mode in the mid flight can be challenging. You would not want to do this if you are new and inexperienced. However, you will still need this when errors occur mid-flight such as the drone moves too slowly, or you realise you have selected a WP that may hit objects, or you did not set your drone to Land at the last WP or at a suitable spot or etc. Do not switch to Land Mode as the drone may fall from the sky! Push the throttle up above the mid throttle level before you switch to Stabilise mode. Prepare to take control over the throttle to prevent it plummeting from the sky. Fly it to safety before you land your drone. If you have pre-set Loiter mode on your transmitter, engage it to take back control from auto-mode, it is easier to control in Loiter Mode since it includes Altitude Hold.

After the path planning is complete, your drone will land at the last WP and the throttle will automatically turn off as soon as it touches the ground. If it doesn’t, pull your throttle fully down and engage stabilise mode, then disarm your drone manually. Disarm your drone by pushing the throttle stick fully to the left at zero throttle position.

Step 97: 14.0 Manual Flight Control

Make sure that you have done with all the calibration and setup in the previous steps. Make sure also you have set all basic required modes ready on the transmitter and on Mission Planner such as Stablise, Altitude Hold, and Land. Refer to “Change the flight mode on mission planner with respect to radio transmitter channel” for more details.

Place your quadcopter on a flat ground in a wide open field and then plug in the battery. Wait until the long beeping sound stops. Then arm your quadcopter by pushing the throttle stick at zero throttle position fully to the right. If this is the first time you arm your quadcopter, you are going to make sure that the directions of your motor rotation are correct. Arm it with your propellers off, and then feel with your finger if the direction of rotation of each motor is correct. Otherwise, interchange any 2 connections (bullet connector) between the specific ESC and motor. Please refer to motor setup in the section “Drone Hardware Setup”.

Step 98: 14.1

If your quadcopter cannot arm, connect your drone to the Mission Planner to see what is causing the pre-arm check to trigger. For example, if the compass offset is too high, you need to re-calibrate your magnetometer. Google search the pre-arm check error message followed by the keyword “Ardupilot” (eg: Compass offset too high Ardupilot) to look for methods to resolve the error.

The pre-arm check’s components can be selectively disabled by going to the Configuring tab > Standard Params > click the ‘Find’ button and search for arm checks. Uncheck ‘All’ and then individually reselect all but the faulty components and then press ‘Write Params’ to save. Make sure you do this after making sure the faulty components will not result in crashes.

Step 99: 14.2

After your quadcopter is armed, i.e. the motors are spinning at minimum speed, push the throttle gently and slowly up until you see your drone begins to lift, give more thrust to help it lift and rise into the air. At your desired altitude, switch to Altitude Hold to remain the altitude. Switch to Loiter mode if you want the drone to stay at the current GPS location while maintaining at the same altitude. Your drone should stay at the last altitude when you switch to these modes. If it falls or descends, you can still push the throttle up to control the flight.

If you do not wish to use the Altitude Hold mode, make sure you are confident at controlling the altitude by constantly pushing the throttle stick up when it descends, and push it back down when it rises, while at the same time controlling the pitch, roll and yaw of your quadcopter. You are advised to test your pilot skill on a cheaper Chinese drone (without Altitude Hold) first before you pilot your self-built drone. Some drones has built-in Altitude Hold ability, and learning over those drones will not help you master the skill of controlling the drone’s altitude manually.

You can begin moving your drone horizontally after your drone is in the air with suitable amount of ground clearance. Your drone moves by rotating around three-axes:

1. Rolling to the left and rolling to the right (Please refer to the transmitter control diagram)

2. Pitching nose down and pitching nose up

3. Yawing to the left (anti-clockwise) and yawing to the right (clockwise)

Step 100: 14.3

Make sure you always monitor the battery voltage using a BB alarm battery voltage monitor. Land your quadcopter as soon as the alarm triggers off. The vertical landing speed can be adjusted together with the descend speed as shown in the section “Running an autonomous mission”. If you do not want to use the Land Mode, slowly descend your quadcopter to the ground by controlling the throttle stick up and down. That again, requires a lot of practices to master a perfect landing. Make sure to try this out on cheaper drones first.

A soon as your quadcopter touches the ground, the throttle will turn off automatically. If it doesn’t, pull your throttle fully down and engage the stabilise mode, then disarm your drone manually. Disarm your drone by pushing the throttle stick fully to the left at zero throttle position.

Step 101: 15.0 Data Flash Log Analysis

Post-flight analysis tells you everything about your flight ranging from barometer altitude, GPS locations, satellite reception, battery voltage, attitude responses, desired attitude, radio communication, speed, motor current, to 3D images of the flight path and modes.

To load the data flash log from Mission Planner, you should not connect the Mission Planner to your drone through a radio telemetry. Instead, you will need to establish udp connection by connecting both (RPi3 and your laptop) to the same LAN and perform necessary telemetry network configuration as shown in the section “Connecting to the Ground Control Station”.

Next, press the data flash log tab as shown above > Download DataFlash Log via Mavlink > and then select the log files of flights (based on accurate time and date) that you want analyse > Download selected files. The downloaded log files will be stored in your PC.

Step 102: 15.1

The downloaded binary log files can be loaded to the Mission Planner for analyses without having to connect to the drone. Simply press ‘Review a Log’ and then open to load the desired flight data based on recorded time and date.

You will be automatically directed to where the flash logs are stored when you want to review them. Otherwise, they can be found in

C:\Users\Username\ Mission Planner\logs\QUADROTOR\1

Step 103: 15.2

Double-click on the selected binary log file to open the flash log. From the flash log, some of the popular and useful parameters in the data flash logs include:

1. Attitude

a. Desired roll/pitch/yaw: Your intended attitude or yaw value from radio

b. Roll/pitch/yaw: Actual attitude and yaw response measured by on-board sensors


a. Alt: Barometer altitude sensing

3. ThO: Output Throttle value

4. GPS

a. NSats: Number of satellite reception

b. HDOP: Horizontal Dilution of Precision to tell GPS accuracy

c. Lat: Latitudinal coordinates throughout the flight

d. Lng: Longitudinal coordinates throughout the flight

e. Alt: GPS measured altitude

f. Spd: Speed

g. GCrs: Ground Course (Heading of quadcopter)

5. IMU

a. Gyr X/Y/Z: Gyroscope IMU data

b. Acc X/Y/Z: Accelerometer IMU data

6. RCIN: Input radio channel value


a. C1/C2/C3/C4: Motor current for Motor 1 to 4


a. Vibe X/Y/Z: Vibration in different axes

Step 104: 15.3

Simply check the box of the parameter you want to analsye on the bottom right panel and the respective graph of that parameter will be generated. It is advisable to uncheck unrelated parameters before you analyse a new parameter so that the graph’s scale can be reset suitably. To increase the size of the graph, move your cursor to the double dotted lines and then drag it down to expand the graph. This takes up in turn the space below it.

If you want to save the graph, right-click and ‘save image as’. Even easier, use a Snipping tool to crop wherever you want to save or copy. The link to download Snipping Tool is as follow:

It requires Java tools to work: The link to download Java is as follows

Step 105: 15.4

The flight data is useful to find out reasons behind crashes, malfunctionalities, or inability to carry out specific functions. For example, if the quadcopter keeps falling down in the Altitude Hold mode, look at the barometer data to see if the barometer sensing of altitude is working properly.

Step 106: 15.5

Together with the downloaded binary log files is the KMZ file of the flight. KMZ files can be opened using the Goggle Earth pro software. Navigate in your PC to C:\Users\Username\ Mission Planner\logs\QUADROTOR\1 and then open the KMZ file with Google Earth Pro.

From Google Earth Pro, you will be able to analyse your flight in 3D street view,

Step 107: 15.6

3D street view image can be observed using Google earth pro. Different flight paths are differentiated based on the switch of flight modes as shown on the left panel above. The flight paths can be deselected from the list as shown in the left panel. Unchecked flight modes will disappear from the 3D map leaving only the checked flight path. From the diagram above, green path is the first lap of auto mode flight path the quadcopter has followed through while the overlapping purple path is the second lap of auto mode.

Horizontal distance measurement of the flight path can be done using the ruler tool in the software.

Step 108: 16.0 Object Avoidance Implementation

APM supports object avoidance in a maximum of 2 directions at most. Through the LV-MaxSonar-EZ0 high performance sonar by Maxbotix, the quadcopter is able to avoid obstacles up to a range of 6.45 m. This expensive EZ0 sensor is used only for object detection above the quadcopter, to avoid hitting objects when the quadcopter takes off or rises. The connection of the MaxSonar to Navio2 FC is through the analog to digital converter (ADC) pins, connecting as shown in below, the voltage, ground and analog pin from the FC to the sonar. To establish physical connection, the micro-header pin for the 6-pin ADC adopted by Navio2 had to be purchased online. The header pins will also fit the other ports so long the number of pins matches.

Step 109: 16.1

As studied, a 100uF capacitor is added in parallel to the supply to stabilise the voltage supply during times of high current consumption and a 100 Ω resistor connected in series to adjust the high logical state during idle. Together this configuration brings about a consistent values of readings from the MaxSonar sensor.

Settings have been made in the Mission Planner software’s “Full Parameter List” tab to enable the rangefinder and to specify the direction it will act against. Rangefinder orientation is set as 24 for UP orientation and the rangefinder pin is set as 5 with connection to the pin ADC 3 on Navio2 as shown below. Other required settings in the parameter list required are shown. Search for them using the “find” function.

Step 110: 16.2

The real-time sensor data was not shown for all orientations other than down or 25 in the rangefinder tab in initial setup, but was shown in the radius radar initiated from the proximity button in the temps menu initiated by Ctrl-F shortcut key. Note that the 2-Dimensional radar will not show distance when the orientation is set to up, or down.

Step 111: 16.3

After making sure that the sonar was working through monitoring from the radar window and testing out the data with different distances, the quadcopter was then safe for flight with obstacle avoidance. The sensor is mounted properly according to the orientation being set, making sure that no objects from the quadcopter, such as wiring or GPS stand, comes in the pings’ travel path. The quadcopter is armed and then switched to only either guided or altitude hold mode for object avoidance.

Several limitations are underlined in the existing object avoidance system which is currently still under development by Emlid developers. The limitations include expensive ultrasonic sensors, limitations of the modes in which object avoidance can work, and limitation of the directions against which the object avoidance system can work.

Shao Fu from have come up with a solution of using HC-SR04 ultrasonic sensor for the implementation of object avoidance in his YouTube channel

Step 112: 16.4

As shown above, five inexpensive ultrasonic sensors HC-SR04 were used for object detection in the front, right, rear, left and down direction. Arduino microcontroller acts as the processor for the receiving sensor data and generate responses accordingly. Arduino Nano was used because of its small size and relatively lighter weight. The Arduino connections with all sensors were sketched and the complete circuit diagram was drawn.

Step 113: 16.5

This time, the system was connected to the FC through the UART serial port. 5V and ground completes the supply circuit to power the Arduino Nano, while Transmitter (TX) pin of the FC was connected to Receiver (RX) pin of Arduino Nano. Similarly, RX pin of the FC was connected to TX pin at the Arduino. The UART port was initially used for the air module of telemetry to enable communication with the ground module in the GCS. To make way for the object avoidance system a simple modification and an extra component was required so the UART port can be spared.

The trick is to exchange the ground and air module where now the ground module was connected through USB port at the FC, and the air module was connected to the GCS. Details of this is explained in the section “Drone Hardware Setup” under the telemetry component.

Connection points required were being precisely and tightly soldered on a copper board. Jumpers were used to ease out connections and female header pins were soldered on place for the installation of ultrasonic sensors in each direction, as shown below. Again, capacitors and resistors were added to improve consistency of each sensor.

Step 114: 16.6

The software of the object avoidance system was built with the Arduino Software (IDE). For distance measurement, NewPing library was used to retrieve raw sensor data directly in centimetre. To improve overall sensor data consistency, averaged value of 5 sensor readings were taken. It was learnt that sonar outputting zero distance is not uncommon. It happens when the distance of the object is out of the detection range, or when there is a directional uncertainty. To avoid the average values getting affected by such errors, only average values with at least 4 non-zero readings are taken, otherwise discarded.

Pitch and roll responses can be realised by sending mavlink pakages containing signals to override the existing roll and pitch value. From the data flash logs, the input RC channel shows a value nearing 1500 for both pitch and roll values when the quadcopter is stable. When the quadcopter pitches nose down, the value drops below 1500, whereas when pitched up, the value rises above 1500 in the pitch channel. Likewise, when the quadcopter tilts to the right, it rises above 1500, in the roll channel, and vice versa.

Step 115: 16.7

This piece of information is vital because the Mavlink messages that were sent from the Arduino microcontroller to the FC will be the messages to override those values in the respective radio channels. The Arduino software was coded in a way that the change in roll-pitch values increase when the nearest distance detected reduces.

Step 116: 16.8

Responses will not be initiated just as soon as the criteria stated in table above is met. Several other conditions have to be fulfilled at the same time to make sure that responses only take place when necessary and when the environment allows so.

Firstly, the quadcopter will only begin its object avoidance, in any flight modes, when the ‘down’ ultrasonic sensor shows altitude over a certain heights. This stabilises the flight during takeoffs, where unnecessary tilting can lead to parts of the quadcopter hitting the ground. Only after making sure that the quadcopter has sufficient clearance from the ground to perform as defined a pitch or roll, object avoidance will take control of the flight.

Secondly, the object detection distance of a particular sensor has to be ‘near’ as in lesser in distance than a specified value, i.e. 100 cm. ‘Near’ in its context has been defined as a non-zero value – in case obstacles are too far away – below 100 cm.

Thirdly, distance sensor along the same axis has to agree upon a response in a way that the direction for response where the quadcopter will act toward must have no obstacles. In other words, if the difference in the distance of object at the front sensor and that of the rear sensor does not exceed a safe specified value, the quadcopter will not be made to tilt to the back even if there is obstacle that appears to fulfil the first 2 conditions stated.

During the upload of sketch on Arduino Nano, TX and RX pins have to be disconnected from Arduino to the FC. Blinking LEDs on the Arduino signifies certain exchange of information between the 2 components. For instance, Arduino is coded to receive at its RX pins heartbeat signal from the FC for every passing second. In the other way round, the TX pin of Arduino will be sending overriding signal to the FC whenever the conditions stated are fulfilled for a specified set of response to be initiated.

When all conditions fulfil, RC overriding mavlink message containing new RollOut and PitchOut values are sent in a standard UART send function. Because the program runs in loop, as soon as the obstacle is distanced from the particular sensor, the response should stop and return to initialised value of zero pitch or roll, i.e. at 1500.

Tests for object avoidance were carried out by constraining 4 sides of the quadcopter to the PVC rectangular structure built as shown above.