upm/examples/python/mcp2515.py

#!/usr/bin/env python
# Author: Jon Trulson <jtrulson@ics.com>
# Copyright (c) 2016 Intel Corporation.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

from __future__ import print_function
import time, sys, signal, atexit
from upm import pyupm_mcp2515 as MCP2515

def main():
    # Instantiate a MCP2515 on SPI bus 0 using a hw CS pin (-1).
    sensor = MCP2515.MCP2515(0, -1)

    ## Exit handlers ##
    # This function stops python from printing a stacktrace when you
    # hit control-C
    def SIGINTHandler(signum, frame):
        raise SystemExit

    # This function lets you run code on exit, including functions from sensor
    def exitHandler():
        print("Exiting")
        sys.exit(0)

    # Register exit handlers
    atexit.register(exitHandler)
    signal.signal(signal.SIGINT, SIGINTHandler)

    print("Setting loopback mode...")

    # set the mode to loopback mode.  In loopback mode, transmitted
    # packets are sent directly to an appropriate receive buffer
    # without actually going out onto the CAN bus.
    sensor.setOpmode(MCP2515.MCP2515_OPMODE_LOOPBACK);

    # lets build up a packet and try loading it (8 bytes max).
    myPayload = "01234567";
    print("Loading a packet of 8 numbers (0-7) into a TX buffer...")
    sensor.loadTXBuffer(MCP2515.MCP2515_TX_BUFFER0, 0, False, False, myPayload);

    # now lets try to transmit it
    print("Transmitting packet...")
    sensor.transmitBuffer(MCP2515.MCP2515_TX_BUFFER0, True);

    print("Transmit successful")

    # There should now be a packet waiting for us in RXB0
    if (sensor.rxStatusMsgs() == MCP2515.MCP2515_RXMSG_RXB0):
        print("Packet received in RXB0, decoding...")

        # now lets retrieve and print it
        sensor.getRXMsg(MCP2515.MCP2515_RX_BUFFER0);

        sensor.printMsg();
    else:
        print("No packet found, how strange.")

    print("Exiting...")

if __name__ == '__main__':
    main()