title: Bluetooth PS3 gamepad in Python

subject: Hardware - Gamepads and remote controls

author: Anton Vanhoucke

* Table of Contents

{:toc}

The cool thing about the PS3 gamepad is that it's a normal Bluetooth device and connects directly to the Ev3. You can easily run programs in brickman and use the pad without another computer or laptop.

- A PS3 gamepad (also known as Sixaxis controller or Dualshock 3)

- A mini-usb / usb cable

- A working ssh and internet connection to the Ev3 (or other ev3dev device)

- ev3-ev3dev-jessie-2015-12-30.img or later

The PS3 pairing process in Brickman is a little strange, but works fine. Stick exactly to these steps:

1. On the Ev3 brick go to 'Wireless and Networks' > 'Bluetooth'

2. Make sure Bluetooth is Powered and the brick is Visible.

3. Connect the gamepad via a mini usb cable to the Ev3. I used the large usb port next to the micro SD slot.

4. Under Devices a 'PLAYSTATION(R) 3 controller' should show up. But don't pair!

4. Remove the USB cable again.

5. Press the PS3 button on the gamepad.

6. The brick now asks "Authorize service HID?" Press "Accept"

You're done! Whenever you press the PS3 button on the gamepad now, it will try to connect to the ev3 brick. Nice!

If brickman doesn't work or if you don't have a display, like on a BrickPi, `bluetoothctl` is the way to go. The gentoo linux guys wrote [a nice tutorial](https://wiki.gentoo.org/wiki/Sony_DualShock)

Now on to Python. In python we need the evdev (without a 3) to read gamepad events. Here's a quick program that will take the right stick Y axis and use it to set the speed of a motor in port A. Note that motor control is in a separate thread. That's because controlling the motors is much slower than reading the gamepad. Multithreading synchronizes both.

{% highlight python %}

#!/usr/bin/env python

__author__ = 'Anton Vanhoucke'

import evdev

import ev3dev.auto as ev3

import threading

def scale(val, src, dst):

"""

Scale the given value from the scale of src to the scale of dst.

val: float or int

src: tuple

dst: tuple

example: print scale(99, (0.0, 99.0), (-1.0, +1.0))

"""

return (float(val - src[0]) / (src[1] - src[0])) * (dst[1] - dst[0]) + dst[0]

def scale_stick(value):

return scale(value,(0,255),(-100,100))

print "Finding ps3 controller..."

devices = [evdev.InputDevice(fn) for fn in evdev.list_devices()]

for device in devices:

if device.name == 'PLAYSTATION(R)3 Controller':

ps3dev = device.fn

gamepad = evdev.InputDevice(ps3dev)

speed = 0

running = True

class MotorThread(threading.Thread):

def __init__(self):

self.motor = ev3.LargeMotor(ev3.OUTPUT_A)

threading.Thread.__init__(self)

def run(self):

print "Engine running!"

while running:

self.motor.run_forever(duty_cycle_sp=speed)

self.motor.stop()

motor_thread = MotorThread()

motor_thread.setDaemon(True)

motor_thread.start()

for event in gamepad.read_loop(): #this loops infinitely

if event.type == 3: #A stick is moved

if event.code == 5: #Y axis on right stick

speed = scale_stick(event.value)

if event.type == 1 and event.code == 302 and event.value == 1:

print "X button is pressed. Stopping."

running = False

break

{% endhighlight %}

Copy this code into a file on the Ev3 brick to run it. If you do `sudo chmod +x your_file_name.py`, you can even run it from the brickman interface!

I mapped out all codes for you! Here they are:

{% include screenshot.html source="/images/Website/sixaxis_event_codes.png" %}

How cool! No computer needed. Just a gamepad and the ev3 brick.

{% include youtube-embed.html youtube_video_id="brfgF3D5c4k" %}