Create CAN_loopback

Loop back example to test a single CAN interface.

examples/CAN_loopback

@@ -0,0 +1,88 @@
+/* CAN Loopback Example
+ * This example sends a message once a second and receives that message
+ *   no CAN bus is required.  This example will test the functionality 
+ *   of the protocol controller, and connections to it.
+ *   
+ *   Written By: Cory J. Fowler - October 5th 2016
+ */
+
+#include <mcp_can.h>
+#include <SPI.h>
+
+// CAN TX Variables
+unsigned long prevTX = 0;                                        // Variable to store last execution time
+const unsigned int invlTX = 1000;                                // One second interval constant
+byte data[] = {0xAA, 0x55, 0x01, 0x10, 0xFF, 0x12, 0x34, 0x56};  // Generic CAN data to send
+
+// CAN RX Variables
+long unsigned int rxId;
+unsigned char len;
+unsigned char rxBuf[8];
+
+// Serial Output String Buffer
+char msgString[128];
+
+// CAN0 INT and CS
+#define CAN0_INT 2                              // Set INT to pin 2
+MCP_CAN CAN0(10);                               // Set CS to pin 10
+
+
+void setup()
+{
+  Serial.begin(115200);  // CAN is running at 500,000BPS; 115,200BPS is SLOW, not FAST, thus 9600 is crippling.
+
+  // Initialize MCP2515 running at 16MHz with a baudrate of 500kb/s and the masks and filters disabled.
+  if(CAN0.begin(MCP_ANY, CAN_500KBPS, MCP_16MHZ) == CAN_OK)
+    Serial.println("MCP2515 Initialized Successfully!");
+  else
+    Serial.println("Error Initializing MCP2515...");
+
+  // Since we do not set NORMAL mode, we are in loopback mode by default.
+  //CAN0.setMode(MCP_NORMAL);
+
+  pinMode(CAN0_INT, INPUT);                           // Configuring pin for /INT input
+
+  Serial.println("MCP2515 Library Loopback Example...");
+}
+
+void loop()
+{
+  if(!digitalRead(CAN0_INT))                          // If CAN0_INT pin is low, read receive buffer
+  {
+    CAN0.readMsgBuf(&rxId, &len, rxBuf);              // Read data: len = data length, buf = data byte(s)
+
+    if((rxId & 0x80000000) == 0x80000000)             // Determine if ID is standard (11 bits) or extended (29 bits)
+      sprintf(msgString, "Extended ID: 0x%.8lX  DLC: %1d  Data:", (rxId & 0x1FFFFFFF), len);
+    else
+      sprintf(msgString, "Standard ID: 0x%.3lX       DLC: %1d  Data:", rxId, len);
+
+    Serial.print(msgString);
+
+    if((rxId & 0x40000000) == 0x40000000){            // Determine if message is a remote request frame.
+      sprintf(msgString, " REMOTE REQUEST FRAME");
+      Serial.print(msgString);
+    } else {
+      for(byte i = 0; i<len; i++){
+        sprintf(msgString, " 0x%.2X", rxBuf[i]);
+        Serial.print(msgString);
+      }
+    }
+
+    Serial.println();
+  }
+
+  if(millis() - prevTX >= invlTX){                    // Send this at a one second interval. 
+    prevTX = millis();
+    byte sndStat = CAN0.sendMsgBuf(0x100, 8, data);
+
+    if(sndStat == CAN_OK)
+      Serial.println("Message Sent Successfully!");
+    else
+      Serial.println("Error Sending Message...");
+
+  }
+}
+
+/*********************************************************************************************************
+  END FILE
+*********************************************************************************************************/