int main(void) { / configure systick / systick_config(); / configure board / bsp_board_config(); / configure GPIO / can_gpio_config(); / initialize CAN and filter */ can_config(); printf("\r\ncommunication test CAN0, please press WAKEUP key to start! \r\n"); can_struct_para_init(CAN_MDSC_STRUCT, &transmit_message); can_struct_para_init(CAN_MDSC_STRUCT, &receive_message); /* initialize transmit message */ transmit_message.rtr = 0; transmit_message.ide = 0; transmit_message.code = CAN_MB_TX_STATUS_DATA; transmit_message.brs = 0; transmit_message.fdf = 0; transmit_message.prio = 0; transmit_message.data_bytes = 8; /* tx message content */ transmit_message.data = (uint32_t *)(tx_data); transmit_message.id = 0xAA; receive_message.rtr = 0; receive_message.ide = 0; receive_message.code = CAN_MB_RX_STATUS_EMPTY; /* rx mailbox */ receive_message.id = 0x55; receive_message.data = (uint32_t *)(rx_data); can_mailbox_config(CAN0, 0, &receive_message); while(1) { /* test whether the WAKEUP key is pressed */ if(0 == gd_eval_key_state_get(KEY_WAKEUP)) { delay_1ms(100); if(0 == gd_eval_key_state_get(KEY_WAKEUP)) { /* transmit message */ can_mailbox_config(CAN1, 1, &transmit_message); printf("\r\nCAN1 transmit data: \r\n"); for(i = 0; i < 8; i++) { printf("%02x\r\n", tx_data[i]); } /* waiting for the WAKEUP key up */ while(0 == gd_eval_key_state_get(KEY_WAKEUP)); } } communication_check(); } }怎么在接收到数据以后再发送接收到的数据

在接收到数据后，您可以在接收循环中添加发送数据的代码。可以像下面这样修改您的代码：

while (1) {
    /* test whether the WAKEUP key is pressed */
    if (0 == gd_eval_key_state_get(KEY_WAKEUP)) {
        delay_1ms(100);
        if (0 == gd_eval_key_state_get(KEY_WAKEUP)) {
            /* transmit message */
            can_mailbox_config(CAN1, 1, &transmit_message);

            printf("\r\nCAN1 transmit data: \r\n");
            for (i = 0; i < 8; i++) {
                printf("%02x\r\n", tx_data[i]);
            }

            /* waiting for the WAKEUP key up */
            while (0 == gd_eval_key_state_get(KEY_WAKEUP));
        }
    }
    
    // Check if CAN message received
    if (can_receive_flag) {
        can_receive_flag = 0;

        // Process received data here

        // Copy received data to transmit message
        memcpy(tx_data, rx_data, 8);

        /* transmit message */
        can_mailbox_config(CAN1, 1, &transmit_message);

        printf("\r\nCAN1 transmit data received: \r\n");
        for (i = 0; i < 8; i++) {
            printf("%02x\r\n", tx_data[i]);
        }
    }

    communication_check();
}

以上代码在接收到数据后，将接收到的数据复制到发送数据的数组中，并再次发送给CAN总线。请确保在适当的位置设置`can_receive_flag`，以便在接收到数据时设置该标志。同时，请根据您的具体需求进行相应的数据处理。