Your problem is due to the fact that the CAN cell doesn't receive an acknowledge bit. Try to replace ''GPIO_Config(GPIO1, 0x0800, GPIO_AF_PP); //Set port 1.11 as CAN RX '' with ''GPIO_Config(GPIO1, 0x0800, GPIO_IN_TRI_CMOS); //Set port 1.11 as CAN RX (input)'' on both STR71x. You can also use CAN_SetTiming() with the appropriate function input to set the bitrate if the APB clock is not 8MHz (don't forget to use CAN_EnterInitMode(CAN_CR_CCE) and CAN_LeaveInitMode(), before and after the function call). Regards.