File content as of revision 2:49c9430860d1:

/*
 * An example showing how to use the CANnucleo library:
 *
 * Two NUCLEO boards are connected to the same CAN bus via CAN transceivers (MCP2551 or TJA1040, or etc.).
 * Transceivers are not part of the NUCLEO boards, therefore must be added by you.
 * Remember also that CAN bus must be terminated with 120 Ohm resitors on both ends.
 * See <https://developer.mbed.org/users/WiredHome/notebook/can---getting-started/>
 * The same source code is used for both NUCLEO boards, but:
 *      For board #1 compile the example without any change.
 *      For board #2 set BOARD1 to 0
 *
 * Note:
 *  To simplify adding/getting data to/from a CAN message
 *  inserter "<<" and extractor ">>" operators have been defined.
 *  Please be aware that CAN message maximum data length is limited to eight bytes.
 *  To make sure this limitation is not violated I recommend to first compile
 *  your application with DEBUG enabled in "CAN.h" file.
 *  Then run it and check for error messages.
 */ 

#include "mbed.h"
#include "CAN.h"

#define BOARD1    1     // please change to 0 when compiling for board #2

#if defined(BOARD1)
    #define RX_ID   0x100
    #define TX_ID   0x101
#else
    #define RX_ID   0x101
    #define TX_ID   0x100
#endif

DigitalOut      led(LED1);
Timer           timer;
CAN             can(PA_11, PA_12);  // rx, tx
CANMessage      rxMsg;
CANMessage      txMsg;
long int        counter = 0;
volatile bool   msgAvailable = false;

/**
 * @brief   'CAN receive-complete' interrup handler.
 * @note    Called on arrival of new CAN message.
 *          Keep it as short as possible.
 * @param   
 * @retval  
 */
void onMsgReceived() {
    msgAvailable = true;
}

/**
 * @brief   Main
 * @note
 * @param 
 * @retval
 */
int main() {
    can.frequency(500000);                      // Initialize CAN and set bit rate to 500kbs
    can.attach(&onMsgReceived, CAN::RxIrq);     // attach 'CAN receive complete' interrupt handler
    timer.reset();
#if defined(BOARD1)
    led = 1;
    timer.start();
#else
    led = 0;
#endif

    while(1) {
        if(timer.read() >= 2.0) {               // check for timeout
            timer.stop();                       // stop timer
            timer.reset();                      // reset timer (to avaoid repeated send)
            counter++;                          // increment counter
            txMsg.clear();                      // clear Tx message storage
            txMsg.id = TX_ID;                   // set ID
            txMsg << counter;                   // append first data item (always make sure that CAN message total data lenght <= 8 bytes!)
            txMsg << led.read();                // append second data item (always make sure that CAN message total data lenght <= 8 bytes!)
            can.write(txMsg);                   // transmit message
            printf("CAN message sent\r\n");
            led = 0;                            // turn off LED
        }
        if(msgAvailable) {
            msgAvailable = false;               // reset flag for next use
            can.read(rxMsg);                    // read message into Rx message storage
            printf("CAN message received:\r\n");
            printf("  ID     = %#x\r\n", rxMsg.id);
            printf("  Type   = %d\r\n", rxMsg.type);
            printf("  Format = %d\r\n", rxMsg.format);
            printf("  Length = %d\r\n", rxMsg.len);
            printf("  Data   =");            
            for(int i = 0; i < rxMsg.len; i++)
                printf(" %x", rxMsg.data[i]);
            printf("\r\n");            
            if(rxMsg.id == RX_ID) {             // if ID matches
                rxMsg >> counter;               // extract first data item
                rxMsg >> led;                   // extract second data item (and set LED status)
                printf("counter = %d\r\n", counter);
                timer.start();
            }
        }
    }
}