File content as of revision 0:22ffaa4d0128:

#include "mbed.h"

Ticker ticker;
Ticker ticker2;

DigitalOut led1(LED1);
DigitalOut led2(LED2);
DigitalOut led3(LED3);
DigitalOut led4(LED4);

CAN can2(p9, p10);
CAN can1(p30, p29);
char counter = 0;
 
void send() {
    
        led1 = !led1;
        return;
        
    printf("send()\n");
    unsigned char d[8];
    d[0] = d[1] = 0xFF;
    d[2] = 0x00;
    d[3] = 0xaa;
    d[4] = 0xc0;
    d[5] = d[6] = d[7] = 0;

    if(can1.write(CANMessage(0x7C1, (char *)d, 8))) {
        //printf("wloop()\n");
        counter++;
        //printf("Message sent: %d\n", counter);
    } 
    led1 = !led1;
}
 void send2() {
    printf("send()\n");
    unsigned char d[8];
    d[0] = d[1] = 0x55;
    d[2] = 0x00;
    d[3] = 0xaa;
    d[4] = 0xc0;
    d[5] = d[6] = d[7] = 0;

    if(can2.write(CANMessage(0x0301, (char *)d, 8))) {
        //printf("wloop()\n");
        counter++;
        //printf("Message sent: %d\n", counter);
    } 
    led3 = !led3;
}
int main() {
    printf("main()\n");
    can1.frequency(500000);
    can2.frequency(500000);
      ticker.attach(&send, 1);
      ticker2.attach(&send2, 1);
    
    CANMessage msg;
    while(1) {
        //printf("loop()\n");
        if(can2.read(msg)) {
            printf("Message received: %d\n", msg.data[0]);
            led2 = !led2;
        } 
        if(can1.read(msg)) {
            printf("Message received: %d\n", msg.data[0]);
            led4 = !led4;
        } 
        
        wait(0.1);
    }
}