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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...

Comments

  1. Brian, a little positive feedback for you. This little sentence is huge for my project "Since about version 3.3 Python supports Bluetooth sockets natively."

    My project is stuck at Python 2.6, because of PyBluez dependence for SPP profile. It was a complete mystery to me why there is no development of PyBluez, and so little talk of Bluetooth libs on stackoverflow etc. I was stumped, I thought: Am I the only one who uses Bluetooth and Python??? So the mystery is solved: Everyone has apparently moved to Python3 with native Bluetooth. Woohoo! I can't wait to try it.

    ReplyDelete

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