By default the example came configured as MASTER.
/* Use this define to specify if the application runs as master or slave */
#define MASTER
/* #define SLAVE */
/* Definition of the TX and RX message buffers depending on the bus role */
#if defined(MASTER)
#define TX_MAILBOX (1UL)
#define TX_MSG_ID (1UL)
#define RX_MAILBOX (0UL)
#define RX_MSG_ID (2UL)
#elif defined(SLAVE)
#define TX_MAILBOX (0UL)
#define TX_MSG_ID (2UL)
#define RX_MAILBOX (1UL)
#define RX_MSG_ID (1UL)
#endif
If you used the default configuration then the expected frame should be CAN_FD with ID 2 and payload 1 byte with data[0] as 0 or 1.
To check if you receive something pres one of the buttons and you should receive an FD frame with ID 1.