Introduction: Cheerson CX-20 3DR Radio for New Board

Picture of Cheerson CX-20 3DR Radio for New Board

This Instructable is for the Cheerson CX-20 with a different APM board than most other people have. These steps will explain what I mean. There is very little instruction for setting up telemetry with this board, but I managed to figure out how to get it working properly.

Step 1: Telemetry Unit

Picture of Telemetry Unit

This is the Telemetry unit that I am using. It is a 915Mhz model and it comes with the necessary components to install the telemetry.

Here is a link on amazon for this exact unit:

Step 2: Opening Your Quad

Picture of Opening Your Quad

The first thing you need to do is take the top part of your quad off. They supply the tools.

After that you need to locate the box that is in the middle of the craft and open it. There will be a zip tie around yours, you just need to cut it and you can put another one on when your finished if you wish. Once you open the little box there is a piece of foam. That needs to go back on there in a similar fashion it came off.

Step 3: Accessing the Port

Picture of Accessing the Port

After you open it up, take it out carefully and flip it so you can see the underside. There should be a port already soldered onto the board and labeled UART. If this is not there, this Instructables is not for you.

Find the cable that came in your telemetry box that fits the port and plug it in.

Step 4: Clipping Some Wires

Picture of Clipping Some Wires

On the end of the cable that plugs into the port on your APM board, clip the Green and Yellow wires. I would clip them pretty short, you won't be using them on that end of the cable. On the other end (The end that connects to the remote telemetry unit) Leave the wires long and strip the ends.

On the board the Ground and +5v are switched, so you will need to cut them and solder them to the opposite wire. So Red wire will now go the the black one, and the black one will go to the red one. Don't ask me why this is I have no clue.

Step 5: Soldering the Tx and Rx Wires

Picture of Soldering the Tx and Rx Wires

Take 2 extra wires and solder them to the location on the bottom of the first board. Wheres the first board you say. Well just like and arduino, the boards come apart. So carefully pull the boards apart and take the top board and flip it over. It should look like the picture. Those 2 extra wires need to be soldered to those 2 points on the board. These are Rx and Tx pins. Now it doesnt matter which wire goes where because if you mix them up the device simply won't work and you will have to switch them around.

Step 6: Connect the Rx and Tx

Picture of Connect the Rx and Tx

Now you need to solder those wires from the bottom of the board to the cable. You need to use the green and yellow cables that attach to your telemetry device, not the ones connected to the UART port that we clipped earlier.

In my case the White wire from the previous step goes to the green wire and the Black wire goes the yellow wire.

It may be different for you, so to check you need to go to your computer and see if both the ground telemetry (USB end) and the remote telemetry can connect. There should be a solid green light and a blinking red one. If the red one on the remote side is dim, the connections are wrong and you need to switch them.

Step 7: Finishing Up

Picture of Finishing Up

Once you have identified the correct wiring, then your all set to put it some heat shrink tubing on for neatness and put it all back together. Your cheerson should now talk to mission planner


budwyzer made it! (author)2017-03-19

Hello, trying to add Minimosd and Voltage unit to Cx-20. Have a few questions, 1) have not soldered the 5v blob on the Minimosd board yet, wondering??? to get 3dr radio telemetry (later) and Minimosd together should I leave the 12v side intact (does 12v side need to be intact to get both) ....also how do you power the 12v side (do you just run 12v to a set of pins on underside of board to the cam or the vid tx or both, sorry for dumb quiestion)? I'll add pics. (2) When opening up copter shell and doing the wire set up for the UART and battery monitor I noticed a White wire that looked broken on the board on the back side by the battery compartment and another White wire that goes to the CX-20 rx. I have put connectors on the wires and hooked them together but have not powered up copter yet just want to be sure before I power it up, but it is a white wire so don't think but not sure it will fry anything. Thanks in advance if anyone can help, Bud.

aggalitsas (author)2015-03-14

After reading your instructable I switched all wires and came up with red(vcc),green(Tx),yellow(Rx), empty and black(gnd) connected to the UART.I get green steady light and red flashing on the 3dr,I can connect to droidplanner,I get the HUD working but I cannot arm the motors (indoors).Do I need to perform step 5 or is that natural?

Aphire (author)aggalitsas2015-03-14

unfortunately this is normal for the moment. the problem is that the radios have different versions of firmware. I've tried to Google the fix and I have not come up with anything. if you find an answer let me know!

kmclen1565 (author)Aphire2016-07-07

you have to get a FTDI Breakout board (about $3 on Amazon) and update the airmodule that way, it will give you the ability to connect the air side to your PC using a usb to mini or micro usb cable.. or use the 3dr radio configuration it

LewyP (author)2015-12-16

Does anyone have experience with wiring this this board with the minimosd and telemetry unit at the same time? I know some people have wired both to the UART port. I just have not found a clear tutorial as to how to do this. I have purchased a splitter that has the 5pin connector for the UART on one end and the 4pin to the telemetry and 6pin header female connector for the micro minimosd. I just want to make sure the wires are in the correct order for using both. This is the first tutorial I've seen with the new board that soldered the rx and tx. I'm hoping mine would work directly to the UART. Adding the osd to that wiring only increases my confusion. Any advice is appreciated!

kmclen1565 (author)LewyP2016-07-07

the 5 to 4 wire is designed for the APM FC, just make sure you have power, ground,TX and RX. on the APM you have to reverse TX an RX at the FC side I don't know about these

coolarmybrat (author)2016-05-09

I have the same board version with a UART connector; it finally fell off when I kept taking out the connector since my Telemetry(ies) were not working correctly. I finally solder the wires to where the UART connector was but here is the thing, if I put in the 433mhz plug-I am able to pair and update the firmware via SIK radio setup (via Mission Planner), but NO heartbeat when I try to connect normally for flgiht programming. If I use my 915mhz plug, I only get a blue light and never sync with my 915mhz ground module. HELP!

kmclen1565 (author)coolarmybrat2016-07-07

as long as you don't cross the power and ground, you can't hurt either board, so figure those out first the you can trial an error it.. GOOD LUCK!!

NiklasF5 (author)2016-06-09

Thank you so much for this tutorial! I soldered the wires as instructed in step 5, and it works perfectly! Both on the computer and on the phone.

IanW17 (author)2015-09-11

Hi, I have the quanum nova and have the new board also. I've been trying to install the radio for a couple of weeks now and have tried every bit of advice that I've found on multiple forums (mainly switching the wires around in the plug) But have had no luck. I was advised to upload a custom firmware (3.2.1) by nice chap on another forum, which I have but still no joy. I was about to give up until I came across this page and will try soldering the 2 wires soon.

I'm a bit concerned that the custom firmware that I've uploaded was write for the cheerson and wondering if it will still activate the telemetry on the quanum?

Also when I was first playing around by plugging the Uart cable in I noticed that there was a single dull red led flash on the air radio but now Im not getting anything, I haven't broke it have I?

Thanks for any advise

AlexisP12 (author)IanW172015-11-30


We have the same board 3.2.1 and it gives me headache at first but upon trying had it all working.

The picture is right but a bit confusing looking at it. what i did was

1. when facing UART, the last right hole of that is the black wire and opposite of that on left in the ground.

2.Cut the green or blue and yellow wire (dont need it in the UART

3. the Green/Blue and Yellow wire solder it on the TX and RX as indicated on the picture number 5. if it doesn't work try to interchange it and it will 100% work

Aphire (author)IanW172015-09-11

I don't think the firmware will be a problem. The Uart cable is a little bi fishy. If your getting a dull red light that means your Rx and Tx cables are switched. if your getting no light, check your connections and also your positive and negative cables. It is not possible to short the board with the Rx and Tx cables, however it is possible to short the board if your positive and negative are wrong.

IanW17 (author)Aphire2015-09-11

Thanks Aphire. I soldered the 2 wires last night and still got nothing so I guess I've shorted the board some where down the line. If you are looking a the UART board flat on with the UART socket at the top, what side should the black (ground) be?

IanW17 (author)2015-09-23

Hi all, I've finally got my telemetry working thanks to Aphire. Turned out to be a faulty transmitter. Now it's all up and running I've noticed that it's disabled my SWA & SWB-0 switches. Is this normal?

BenjaminM10 (author)2015-06-13

Would this telemetry unit work with the Cheerson CX-20?

Also, I'll be using it with my LG GPad 8.3, any thing you think I should be aware of?

Thanks a lot for your feedback.

BenjaminM10 (author)2015-06-09

@Aphire, which telemetry unit should I use then? Any possibility to use it with Bluetooth?
@js349, any chance you good do a video, I'd love to see how it works on screen. Thanks.

js349 (author)2015-05-15

Could somebody please help me? I have the exact same APM board with the UART connector so I've followed your instructions and I get a green light blinking on both of the telemetry units and when I click connect on my tablet (what I'm using for a computer) in the Tower (Droid Planner) software, the red light blinks on the telemetry unit that is connected to my tablet but the green light continues to blink on the telemetry unit connected to the UART and no other light comes on. Any ideas what I may have done wrong?

Aphire (author)js3492015-05-15

The telemetry unit that is featured in this Instructable is not tablet compatabile

js349 (author)Aphire2015-05-16

Thanks for answering Aphire but I'm really confused about that. I had seen this and thought that was what you could do with this. I thought this was great because you could carry a small tablet out in the field and plot your course there. My Android tablet recognizes the USB module and the module has a green light that comes on and when I click connect, the red light blinks but it doesn't connect with the module plugged in to the UART and the UART module has a green blinking light. I'm using the Android app named Tower (previously named Droid Planner). So when you use a computer, what application do you use? This is what really confuses me because with the open source version of this quad (which is what I have), you can already connect it to a PC and plot a course there with that version of Mission Planner. Is this just for non open source CX-20s?

Aphire (author)js3492015-05-16

Yes the tablet may recognize the usb module, but this is mean't for a laptop. The board on the CX-20 I believe does not support any other program besides Mission planner.

js349 (author)Aphire2015-05-16

OK, well that's disappointing. Now, I've downloaded and installed Mission Planner v1.3.25 to my laptop and started the application and I have my USB module plugged in and the module plugged in on the quad and connected a battery and both units have green blinking lights. When I click connect nothing happens and it just times out. Do I have the wrong version of Mission Planner or did I miss something? Thanks again!

js349 (author)js3492015-05-16

I figured out that I didn't have the correct com port picked and baud rate set but even after I did that, the red light blinks and the software says it is attempting to connect but it never connects to the module on the quad. All I get there is a green blinking light but never see the red light at all. Any ideas?

Aphire (author)js3492015-05-17

Switch the Tx and the Rx wires on the CX-20

js349 (author)Aphire2015-05-18

I'm happy to report that switching the wires worked and I'm very happy to report that it works with my tablet. Now the next step is to learn a little more about Tower before I fly a mission. I was able to upload and download a mission between the CX-20 and my tablet.

BenjaminM10 (author)js3492015-06-09

Hi js349, I'm curious to know your result with you first mission using Tower. How did it go? I was also wondering what kind of telemetry can you receive (GPS connection, Signal, Compass, Altitude, speed, etc.)? Can you also set way points dynamically and follow the CX-20 path on a map? Thanks a lot for your input

js349 (author)BenjaminM102015-06-09

My first mission was fairly short and I haven't been able to fly any more because I can't get a good enough GPS signal at my house due to tall trees all around so I've got to find an open field where I can test it better (look on Youtube to see people who have flown missions). The Tower software shows/tells you about your GPS connection and all of the other items you asked about. And, you can draw your flight path on your tablet, create way points dynamically and follow the path. I did find out that you need to change a parameter for the CX-20 to face the way point that it is traveling towards and that is the WP_YAW_BEHAVIOR to 2.

js349 (author)Aphire2015-05-18

Thanks Aphire! That is what I'm going to try next when I have a chance to take it apart again. I put it all back together to make sure it would still fly after the soldering and it does fly like it did before.

bullseye123 (author)2015-04-25

Hi, I have the exact same telemetry kit, I first plugged everything in, found that no light is coming on, then I swapped the power like said after testing the voltage with my volt meter, I found power on the tx and rx to ground too just to make sure, still nothing worked, then I soldered as you said, and still nothing work, the tx is not coming on, I have tested the voltage does get to the tx, and the solder is done properly I have now spend 5 ours on this, so either something is disabled via software, or this brand new tx is faulty, the rx with usb works fine in my pc. any input will help a lot. thank you.

PhilT5 (author)bullseye1232015-05-30

Hi, could you resolve your issue? I think I have the exact same problem. Any help would be really appreciated.

Aphire (author)bullseye1232015-04-25

Is there any faint lights coming on? Sometimes the lights are faint and you can barely see them. If thats the case, switch the rx and tx. Otherwise, try making the telemetry unit power on with some other 5v power source. If none of that works comment again and ill see if i can find anything else

bullseye123 (author)Aphire2015-04-26

Hi Aphire, Thank you for the reply: No faint light's coming on. I switched the rx and tx multiple times with no luck. I have an arduino uno board that gives out 5v and I plugged it in there. still nothing working. Im just spitballing here, could something have damaged the first time I plugged it in without the 5v and ground swopped ?

Aphire (author)bullseye1232015-04-29

Sorry for the late reply! Possibly.. but i did the same thing and mine is fine.. Could you attach images to another comment so i can see exactly how you have done it?

aabelix (author)2015-05-21

Hi, Just looking the circuit diagram and think if I remove resistors R49 and R50 from second serial port is what is routed to the telemetry pads on the APM UART connector, then you can solder jumper wires to the microprocessor side of the IO protection resistors to connector side removed resistors pads and you can get right RX and TX data directly to UART connector. But I will do more measurements :-)

PascalB1 (author)2015-05-06

Hi Aphire, thank you so much for your topic, it solved my problem! Just one thing: in order to simplify the process, I soldered the TX and RX (UART side) cables direcly on board point without clipping them. It's very easy to pull them out of the connector, so no need for extra 2 wires.

Aphire (author)PascalB12015-05-06

Very good point. In the midst of figuring all of this out, I cut my cable too short, which is why I needed extra wires.

meikdre (author)2015-04-27

Any ideas from where I can recycle the cable? I don't have the cable and thought it might be in some kind of eletronics (but did not find it in my pc, cd drive...)?!

Aphire (author)meikdre2015-04-29

Im not sure... But the telemetry kit should have come with all the cables you would need

AlejandroR3 (author)2015-04-21

Thank you so much for putting this together! So just to be clear if I have the UART port already soldered, do I still need to solder something else? Also do you know how to add the power module? Thanks!

Aphire (author)AlejandroR32015-04-22

The only thing you will need to solder is the TX and RX things. they are in the instructable instructions. I am not quite sure what you mean by power module. The Cheerson CX-20 comes with a connector for battery packs

elricfate (author)2015-03-12

Totally making this a favorite for when my CX-20 gets here, just ordered it so it's likely got the new board.

CCollado (author)2015-02-19

Don't understand step 5. I plugged mine in to the uart with 5pin connector and 4 pin to the telemetry and it worked fine. Also it looks like your wires are in the wrong order. It should be red, green, yellow, skip a pin and black in the last pin (left to right). That might be why you have the extra tx/rx wiring. You shouldn't need step 5.

Aphire (author)CCollado2015-02-19

yes you shouldn't need step 5. There is either a problem with the telemetry wiring, or someone screwed up my flight controller. either way, step 5 Is necessary for some people

CCollado (author)2015-02-19

This was a surprise when I opened up the FC. I was ready to sodder it to the board. Just plugged in my telemetry and boom connected to MP right away.

Aphire (author)CCollado2015-02-19

well congrats! glad yours worked right off the bat

MsSweetSatisfaction (author)2015-01-31

This is so awesome information, definitely great for any quadcopter enthusiast. Welcome to instructables, I hope we see more from you in the future!

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