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In this very short tutorial, I will show you how to controll 2 servos wired on your RaspberryPi. This tutorial is very simple and flexible because of its multiple applications. So, let's start !

If you are bored about reading, I made 2 videos on this subject (in French).

Step 1: Some Stuff

To begin, let me introduce you the stuff we will need to start the project.

We will need :

  1. 1 Raspberry Pi (we do not care about the model)
  2. 1 Bluetooth USB dongle (generally they are relatively cheap, get some here)
  3. 2 Servos (get some here)
  4. 1 WiiMote (get one here)
  5. Some wire (you will see why later)

This is the entire stuff we will need to build this project. Now let's make !

Step 2: Preparing the Pi !

When you are ready, plug the power into your Pi and start by cloning this Git repository into your Home by typing this command :

sudo git clone https://github.com/richardghirst/PiBits.git

After go into the Servod directory by typing :

cd ~/PiBits/ServoBlaster/user/

And compile the program :

sudo make

Next step, we will wire the servos and configure ServoBlaster to make our servos controllables.

Step 3: Wiring the Servos

On the S3003 servos, you should see that there are 3 entries : the red is for the power, black for ground and the white one for the signal.

Powering the servos is very simple, just plug the red wire on a 5V GPIO pin of your Raspberry Pi, after that, plug the black wire on a ground pin.

List of the 5V GPIO pins : 2,4.
List of the ground pins : 9,14,25,30,34,39.

For the signal wire, you have to plug it in basic GPIO pins; I usually plug them in pins 7 (GPIO4) and 11 (GPIO17). The main thing you have to do is remebering which servo is wired to these pins (e.g. pan in on 7 and tilt is on 11) to configure the program.

So, let's configure the program !

Step 4: Configuring ServoBlaster

Once you have wired your servos and you remember the numbers of the pins, start by going into Servod directory :

cd ~/PiBits/ServoBlaster/user/

Here, just type :

./servod

You should see somthing like that :

$ sudo ./servod
Board revision: 1
Using hardware: PWM
Using DMA channel: 14
Idle timeout: Disabled
Number of servos: 8
Servo cycle time: 20000us
Pulse increment step size: 10us
Minimum width value: 50 (500us)
Maximum width value: 250 (2500us)
Output levels: Normal

Using P1 pins: 7,11,12,13,15,16,18,22

Servo mapping:

0 on P1-7 GPIO-4
1 on P1-11 GPIO-17
2 on P1-12 GPIO-18
3 on P1-13 GPIO-21
4 on P1-15 GPIO-22
5 on P1-16 GPIO-23
6 on P1-18 GPIO-24
7 on P1-22 GPIO-25

After that enter this line (pins 7 and 11 are used as examples, you can use yours of course):

./servod --p1pins=7,11

This line will specify that 2 signal wire are plugged, one on GPIO7 and the other on GPIO17.

You can now try to make rotate your servos by typing :

sudo echo P1-7=0% > /dev/servoblaster
sudo echo P1-11=0% > /dev/servoblaster
sudo echo P1-7=100% > /dev/servoblaster
sudo echo P1-11=100% > /dev/servoblaster

You should have noticed that the 4 commands entered are usually used to write text into files.

Now, we can setting up Bluetooth to connect our WiiMote to the Pi !

Step 5: Setting Up Bluetooth and WiiMote

Start by plugging your Bluetooth USB dongle into your Pi and reboot it. Next, run :

lsusb

If your dongle appears, all right, we can continue ! If it not appears, retry...

Now, we need to install the drivers and softwares, type :

sudo apt-get update
sudo apt-get install bluetooth

If the installation ends without APT or DPKG error message, you can continue else, try to solve the problem by typing sudo apt-get -f install and then retry sudo apt-get install bluetooth --fix-missing .

After that check if the Bluetooth service is running :

sudo service bluetooth status

You should see something like :
[ok] bluetooth is running.

If the service not seems to be running, try sudo /etc/init.d/bluetooth start

If all these steps worked correctly, now let's code !

Step 6: Installing the CWiiD Python Library

In order to get informations from the Wiimote through Bluetooth, we have to install a Python library called CWiiD, it is like a "driver" if you want. To install it, it is very simple, juste type :

sudo apt-get install python-cwiid

That's it, now let's code (really) !

Step 7: Coding the Python Script

To get the script just type :

sudo nano ~/wiimote-script.py

Then, copy and paste the piece of code at https://github.com/Cypaubr/WiimoteServos/blob/mast...

Ctrl+O, ENTER and Ctrl+X to save and quit.

Now, it's time to run the script !!!

Step 8: Running the Script

To run the script just type :

sudo python wiimote-script.py

You should now be able to control your servos from your Wiimote.

If the programms throws an erre like

/dev/servoblaster File not found

You just have to relaunch the servod program from Step 4...

<p>You should never connect your Pi's 5V supply to servos. The servos can cause a voltage drop which may damage your Pi, or at the very least cause it to reboot, possibly causing SD card corruption</p>
<p>Yes, I know it but it is just for the time of the tutorial, for educational purposes. Normally, a voltage drop does not appear if you do not force the servos. But it is true that if I would like to make a real application with that I should use a self-powered servo board. Thank you !</p>
<p>Wiimotes are so useful! I've used them for a few different projects! Thanks for sharing! </p>
<p>You are welcome !</p>

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