pyCandapter

pyCandapter is a Python module for interfacing with the Candapter USB to CAN adapter. It uses the pySerial module to communicate with the Candapter. The python-can module is used to create and read CAN messages. The module is designed to be used with Python 3.8 and above.

Usage

• Install required modules.

  pip install pyserial
  pip install python-can

• Download the pyCandapter module and place it in the same directory as your Python script.

• Import necessary modules.

  import pyCandapter
  import can
  import signal

• Identify the COM port and baud rate of the Candapter. (This can be found through the Device Manager in Windows). Also define the CAN baud rate.

  PORT = 'COM7'
  SERIALBAUDRATE = 9600
  CANBAUDRATE = 250000

• Create a Candapter object and open the CAN bus on the Candapter.

  candapter = pyCandapter.pyCandapter(PORT, SERIALBAUDRATE)
  candapter.openCANBus(CANBAUDRATE)

• Set up a signal handler to close the CAN bus and serial port when the script is terminated.

  def signal_handler(sig, frame):
      candapter.closeCANBus()
      exit(0) 
  
  signal.signal(signal.SIGINT, signal_handler)

• To receive CAN messages, use the following code.

  while True:
      message = candapter.readCANMessage()
      if message is not None:
          print(message)

  The message is a python-can message object. The documentation for the same can be found here.

• To send a CAN message, use the following code.

  message = can.Message(arbitration_id=0x123, data=[0, 1, 2, 3, 4, 5, 6, 7], is_extended_id=False)
  candapter.sendCANMessage(message)

The full file can be found here.

Known Issues

• If the error "Error setting baudrate" appears, it is likely that the previous connection was not closed properly. Disconnect the Candapter and reconnect it, then try again.
• If the error "SerialException: could not open port 'COMx': PermissionError(13, 'Access is denied.', None, 5)" is encountered, it is likely that the COM port is already open in another application. Close the application and try again.
• If the error "SerialException: could not open port 'COMx': FileNotFoundError(2, 'The system cannot find the file specified.', None, 2)" is encountered, it is likely that the COM port is not connected to the computer. Connect the Candapter and try again.
• There is no support for reading extended CAN messages at the moment.