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/javascript/mcp2515-txrx.js

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+/*
+ * 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.
+ */
+
+var sensorObj = require('jsupm_mcp2515');
+
+// Instantiate a MCP2515 on SPI bus 0 using a hw CS pin (-1).
+var sensor = new sensorObj.MCP2515(0, -1);
+
+// 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.
+
+function transmit(sensor)
+{
+    // lets build up a packet and try loading it (8 bytes max).
+    var myPayload = "01234567";
+    console.log("Loading a packet of 8 numbers (0-7) into a TX buffer...");
+    sensor.loadTXBuffer(sensorObj.MCP2515_TX_BUFFER0,
+                        0, false, false, myPayload);
+
+    // now lets try to transmit it
+    console.log("Transmitting packet...");
+    sensor.transmitBuffer(sensorObj.MCP2515_TX_BUFFER0, true);
+
+    console.log("Transmit successful");
+    console.log();
+}
+
+function receive(sensor)
+{
+    // There should now be a packet waiting for us in RXB0
+    if (sensor.rxStatusMsgs() == sensorObj.MCP2515_RXMSG_RXB0)
+    {
+        console.log("Packet received in RXB0, decoding...");
+
+        // now lets retrieve and print it
+        sensor.getRXMsg(sensorObj.MCP2515_RX_BUFFER0);
+
+        sensor.printMsg();
+        console.log();
+    }
+}
+
+// by default we just receive packets
+if (process.argv.length > 2)
+{
+    // transmit mode
+    interval = setInterval(function() { transmit(sensor); }, 500);
+}
+else
+{
+    // receive mode
+    interval = setInterval(function() { receive(sensor); }, 100);
+}
+
+process.on('SIGINT', function()
+{
+    sensor = null;
+    sensorObj.cleanUp();
+    sensorObj = null;
+    console.log("Exiting...");
+    process.exit(0);
+});