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Receive CAN FD messages

refer to NTCAN Application Developers Manual document charpter

• 1.4.2 Integration and Migration
• 8.2 Receiving messages (Classical CAN and CAN FD)

example code

fd_rcv.c：程序展示如何调用NTCAN API来读取接收到的CAN FD消息。 如下code snippet是需要注意的内容。

uint32_t mode=NTCAN_MODE_FD; /* Mode bits for canOpen */
NTCAN_BAUDRATE_X baud; /* Bit rate configuration */
CMSG_X cmsg[8]; /* Buffer for can messages */

baud.mode = NTCAN_BAUDRATE_MODE_INDEX;
baud.flags = NTCAN_BAUDRATE_FLAG_FD;
baud.arb.u.idx = NTCAN_BAUD_1000; /* Nominal bit rate: 1000KBit/s */
baud.data.u.idx = NTCAN_BAUD_5000; /* Data phase bit rate: 5 MBit/s */
retvalue = canSetBaudrateX(rxhandle, &baud);

for(;;) {
        /*
        * Set max numbers of messages that can be returned with
        * one canReadX() call according to buffer size.
        */
        len = 8;
        retvalue = canReadX(rxhandle, &cmsg[0], &len, NULL);
        if (retvalue == NTCAN_RX_TIMEOUT)
        {
            printf("canReadX() returned timeout\n");
            continue;
        }
        else if(retvalue != NTCAN_SUCCESS)
        { 
            printf("canReadX() failed with error %d!\n", retvalue);
        }
        else
        { 
            printf("Function canReadX() returned OK !\n");
            printf("ID of received message :%x!\n", cmsg[0].id);
            printf("DLC of received message :%x!\n", NTCAN_DLC(cmsg[0].len));
            if(NTCAN_IS_FD(cmsg[0].len)) {
                // printf("BRS of received message :%x!\n", !NTCAN_IS_FD_WITHOUT_BRS(cmsg[0].len));
                if(NTCAN_IS_FD_WITHOUT_BRS(cmsg[0].len))
                    printf("CAN FD without BRS!\nThe bit rate of data phase is NOT changed.\n");
                else
                    printf("CAN FD with BRS!\nThe bit rate of data phase is changed.\n");
            } else 
            {
                printf("RTR of received message :%x!\n", NTCAN_IS_RTR(cmsg[0].len));
            }
            for (i=0;i<NTCAN_LEN_TO_DATASIZE(cmsg[0].len);i++)
                printf("Byte %d of received message :%x!\n", i, cmsg[0].data[i]);
        }
        break;
    };

程序运行

首先建立一个CAN FD的总线。本人Demo总线系统上有两个设备，一个设备为esd CAN-PCIe/402-B4-FD安装在Ubuntu台式电脑上，上述的example code编译和运行在此电脑上。另一个设备为CAN-USB/3-FD连接到Win11笔记本电脑，此笔记本电脑上安装了最新版的CANreal软件。

参考CANreal中CAN FD的章节，向总线发送CAN FD的消息。编辑CAN FD消息时可以尝试勾选/不勾选"No bitrate switch(CA FD -BR)"的选项。接收端运行example code等待接收并解析CAN FD消息。