Simple script for calculating filter and mask for CAN bus communication

CANBusFilterMaskGenerator.py

#!/usr/bin/python
#
# Copyright (C) 2018 Kristian Lauszus, Candela. All rights reserved.
#
# Contact information
# -------------------
# Kristian Lauszus
# Web      :  http://www.lauszus.com
# e-mail   :  lauszus@gmail.com

import operator
from functools import reduce


def can_bus_filter_mask(can_bus_ids, quiet=True, verbose=False):
    if verbose:
        print('[{}]'.format(', '.join([hex(x).upper() for x in can_bus_ids])))

    # Calculate CAN Bus filter and mask
    can_bus_filter = reduce(operator.and_, can_bus_ids)  # Simply bitwise AND all IDs together

    can_bus_mask = reduce(operator.or_, can_bus_ids) ^ can_bus_filter  # Get bits that are not constant among the IDs
    # We can use all bits except these ones for the mask, so simply flip bits according to current format
    if reduce(operator.or_, can_bus_ids) > 0x7FF:  # Check if using extended format
        can_bus_mask ^= 0x1FFFFFFF  # Extended format = 29 bits
    else:
        can_bus_mask ^= 0x7FF  # Base format = 11 bits

    # Just to make sure that it is calculated correctly
    for can_bus_id in can_bus_ids:
        assert can_bus_id & can_bus_mask == can_bus_filter, 'Error: 0x{:03X}'.format(can_bus_id)

    if not quiet:
        print('Filter: 0x{:03X}'.format(can_bus_filter))
        print('Mask: 0x{:03X}'.format(can_bus_mask))

    if not quiet:
        if can_bus_filter <= 0x7FF:
            can_bus_received_id_count = 0
            for can_bus_id in range(0, 0x7FF + 1):
                if can_bus_id & can_bus_mask == can_bus_filter:
                    can_bus_received_id_count += 1
                    if verbose:
                        print('ID: 0x{:03X} will be received'.format(can_bus_id))
            print('{} ID\'s will be received\n'.format(can_bus_received_id_count))
        else:  # It takes too long to loop through all extended IDs
            for can_bus_id in can_bus_ids:
                if can_bus_id & can_bus_mask != can_bus_filter:
                    print ('ID: 0x{:03X} will NOT be received'.format(can_bus_id))

    return can_bus_filter, can_bus_mask


# noinspection PyPep8Naming
def main():
    # See: http://www.cse.dmu.ac.uk/~eg/tele/CanbusIDandMask.html
    # ids = range(0, 0x1FFFFFFF + 1)  # Extended format example
    # ids = range(0, 0x7FF + 1)  # Base format example

    inverter_id = 0x01
    INVERTER_INFO = 0x12C, 0x136, 0x140, 0x14A, 0x154
    ids = [x + inverter_id for x in INVERTER_INFO]
    can_bus_filter_mask(ids, False)

    node_ids = [inverter_id]  # Set all the node ID's here
    CANOPEN_EMCY, CANOPEN_HEARTBEAT = 0x080, 0x700
    ids = [msg + node for node in node_ids for msg in [CANOPEN_EMCY, CANOPEN_HEARTBEAT]]
    can_bus_filter_mask(ids, False)

    bms_error_ids = [list(range(0x100, 0x100 + 8)), # General frames
                    list(range(0x200, 0x200 + 8)) + [0x200 + 256]]  # Error last seen
    for ids in bms_error_ids:
        can_bus_filter_mask(ids, False, True)


if __name__ == '__main__':
    main()