[mbed][LPC17XX] Implement CAN::mode for LPC176X

Implement all CAN modes except for GlobalTest and SilentTest on on the LPC17XX

Author: devanlai

libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/can_api.c

@@ -79,7 +79,45 @@ static inline void can_enable(can_t *obj) {
 }
 
 int can_mode(can_t *obj, CanMode mode) {
-    return 0; // not implemented
+    int success = 0;
+    switch (mode) {
+        case MODE_RESET:
+            // Clear all special modes
+            can_reset(obj);
+            obj->dev->MOD &=~ 0x06;
+            success = 1;
+            break;
+        case MODE_NORMAL:
+            // Clear all special modes
+            can_disable(obj);
+            obj->dev->MOD &=~ 0x06;
+            can_enable(obj);
+            success = 1;
+            break;
+        case MODE_SILENT:
+            // Set listen-only mode and clear self-test mode
+            can_disable(obj);
+            obj->dev->MOD |=  0x02;
+            obj->dev->MOD &=~ 0x04;
+            can_enable(obj);
+            success = 1;
+            break;
+        case MODE_TEST_LOCAL:
+            // Set self-test mode and clear listen-only mode
+            can_disable(obj);
+            obj->dev->MOD |=  0x04;
+            obj->dev->MOD &=~ 0x02;
+            can_enable(obj);
+            success = 1;
+            break;
+        case MODE_TEST_SILENT:
+        case MODE_TEST_GLOBAL:
+        default:
+            success = 0;
+            break;
+    }
+
+    return success;
 }
 
 int can_filter(can_t *obj, uint32_t id, uint32_t mask, CANFormat format, int32_t handle) {
@@ -316,6 +354,12 @@ int can_write(can_t *obj, CAN_Message msg, int cc) {
     const unsigned int *buf = (const unsigned int *)&m;
 
     CANStatus = obj->dev->SR;
+
+    // Send the message to ourself if in a test mode
+    if (obj->dev->MOD & 0x04) {
+        cc = 1;
+    }
+
     if (CANStatus & 0x00000004) {
         obj->dev->TFI1 = buf[0] & 0xC00F0000;
         obj->dev->TID1 = buf[1];