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Bluetooth with Python 3.3

Since about version 3.3 Python supports Bluetooth sockets natively. To put this to the test I got hold of an iRacer from sparkfun. To send to New Zealand the cost was $60. The toy has an on-board Bluetooth radio that supports the RFCOMM transport protocol.



The drive protocol is dead easy, you send single byte instructions when a direction or speed change is required. The bytes are broken into two nibbles: 0xXY where X is the direction and Y is the speed. For example the byte 0x16 means forwards at mid-speed. I was surprised to note the car continues carrying out the last given demand!

I let pairing get dealt with by the operating system. The code to create a Car object that is drivable over Bluetooth is very straight forward in pure Python:

import socket
import time

class BluetoothCar:
    def __init__(self, mac_address="00:12:05:09:98:36"):
        self.socket = socket.socket(socket.AF_BLUETOOTH, socket.SOCK_STREAM, socket.BTPROTO_RFCOMM)
        self.socket.connect((mac_address, 1))
    
    def _write(self, data_byte):
        self.socket.send(bytes([data_byte]))
    
    def drive(self, command, duration=1.0):
        self._write(command)
        time.sleep(duration)
        self.stop()
        
    def forwards(self, duration=1.0):
        self.drive(0x16, duration)
        
    def reverse(self, duration=1.0):
        self.drive(0x26, duration)

    def left(self, duration=1.0):
        self.drive(0x57, duration)

    def right(self, duration=1.0):
        self.drive(0x67, duration)

    def stop(self):
        self._write(0x00)
    
    def __del__(self):
        self.stop()

if __name__ == "__main__":
    car = BluetoothCar()
    while True:
        car.forwards(0.05)

So there is no need for PyBluez or any of that overhead for some easy Bluetooth tasks. From here it is very easy to build up a program to control the car from the interface of your desire:  keyboard, mouse, joystick, internet, webcam...

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