mcp2515: Initial implementation; C; C++

The mcp2515 is a CAN bus controller.  It was developed using the Seeed
CAN bus shield.

Signed-off-by: Jon Trulson <jtrulson@ics.com>

examples/python/mcp2515-txrx.py

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+#!/usr/bin/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)
+
+    # by default we just receive packets
+    do_tx = False;
+    if (len(sys.argv) > 1):
+        do_tx = True
+
+    # NOTE: This example assumes that only two devices are connected
+    # to the CAN bus, and that both devices are running this example;
+    # one in TX (transmit) mode, and one in RX (receive) mode.
+
+    # If this is not the case, then in rx mode you may see other
+    # packets from other devices, or not, depending on whether the
+    # speed is correct for the network.  In tx mode, errors may be
+    # generated on the bus, especially if the CAN bus speed does not
+    # match the rest of the network.
+
+    # You should start the receiver example first.  The transmitter
+    # example will fail after about 5 seconds (timeout) of not being
+    # able to transmit a message.
+
+    # By default, after initialization, the baud rate is set to
+    # 50Kbps, and the mode is NORMAL, so we don't need to set any of
+    # that here.
+
+    while (True):
+        if (do_tx):
+            print("Loading a packet of 8 numbers (0-7) into a TX buffer...")
+            myPayload = "01234567";
+            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")
+            print()
+            time.sleep(.5)
+        else:
+            # RX mode
+            # Look for 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();
+                print()
+
+    print("Exiting...")
+
+if __name__ == '__main__':
+    main()

examples/python/mcp2515.py

@@ -0,0 +1,79 @@
+#!/usr/bin/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()