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/c/mcp2515.c

@@ -0,0 +1,101 @@
+/*
+ * 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.
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+
+#include "mcp2515.h"
+
+int main(int argc, char **argv)
+{
+//! [Interesting]
+
+    // Instantiate a MCP2515 on SPI bus 0 using a hw CS pin (-1).
+    mcp2515_context sensor = mcp2515_init(0, -1);
+
+    if (!sensor)
+    {
+        printf("mcp2515_init() failed\n");
+        return 1;
+    }
+
+    printf("Setting loopback mode...\n");
+
+    // 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.
+    if (mcp2515_set_opmode(sensor, MCP2515_OPMODE_LOOPBACK))
+    {
+        printf("mcp2515_set_opmode(loopback) failed.\n");
+        return 1;
+    }
+
+    // lets build up a packet and try loading it.
+    uint8_t myPayload[8] = {0, 1, 2, 3, 4, 5, 6, 7};
+    printf("Loading a packet of 8 numbers (0-7) into a TX buffer...\n");
+    if (mcp2515_load_tx_buffer(sensor, MCP2515_TX_BUFFER0, 0, false, false,
+                               myPayload, 8))
+    {
+        printf("mcp2515_load_tx_buffer() failed\n");
+        return 1;
+    }
+
+    // now lets try to transmit it
+    printf("Transmitting packet...\n");
+    upm_result_t rv = 0;
+    if ((rv = mcp2515_transmit_buffer(sensor, MCP2515_TX_BUFFER0, true)))
+    {
+        printf("mcp2515_transmit_buffer() failed with code %d\n", rv);
+        return 1;
+    }
+
+    printf("Transmit successful\n");
+
+    // There should now be a packet waiting for us in RXB0
+    if (mcp2515_rx_status_msgs(sensor) == MCP2515_RXMSG_RXB0)
+    {
+        printf("Packet received in RXB0, decoding...\n");
+
+        // now lets retrieve it
+        MCP2515_MSG_T msg;
+        if (mcp2515_get_rx_msg(sensor, MCP2515_RX_BUFFER0, &msg))
+        {
+            printf("mcp2515_get_rx_msg() failed\n");
+            return 1;
+        }
+
+        mcp2515_print_msg(sensor, &msg);
+    }
+    else
+    {
+        printf("No packet found, how strange.\n");
+    }
+
+    printf("Exiting...\n");
+
+    mcp2515_close(sensor);
+//! [Interesting]
+
+    return 0;
+}