【MCX-N947-BRK板卡试用】-1-CAN回环模式测试

SensorYoung

之前论坛分享关于CAN的一个帖子，温故知新：好文分享-关于CAN通讯，你拎不清的几个概念


MCX-N系列有两路CAN，分别为CAN0和CAN1，其内部框图如下：


其工作模式有如下5种：


设置CAN0的时钟：

1.     /* attach FRO HF to FLEXCAN0 */
   
2.     CLOCK_SetClkDiv(kCLOCK_DivFlexcan0Clk, 1u);
   
3.     CLOCK_AttachClk(kFRO_HF_to_FLEXCAN0);

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设置工作模式为loopback，CAN速率 500K bps：

1. flexcanConfig.enableLoopBack = true;
   
2. flexcanConfig.bitRate = 500000U;

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设置RX message buffer:

1. /* Setup Rx Message Buffer. */
   
2.     mbConfig.format = kFLEXCAN_FrameFormatStandard;
   
3.     mbConfig.type   = kFLEXCAN_FrameTypeData;
   
4.     mbConfig.id     = FLEXCAN_ID_STD(0x123);
   
5. #if (defined(USE_CANFD) && USE_CANFD)
   
6.     FLEXCAN_SetFDRxMbConfig(EXAMPLE_CAN, RX_MESSAGE_BUFFER_NUM, &mbConfig, true);
   
7. #else
   
8.     FLEXCAN_SetRxMbConfig(EXAMPLE_CAN, RX_MESSAGE_BUFFER_NUM, &mbConfig, true);
   
9. #endif

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设置Tx message buffer以及tx frame的报文内容：

1. /* Setup Tx Message Buffer. */
   
2. #if (defined(USE_CANFD) && USE_CANFD)
   
3.     FLEXCAN_SetFDTxMbConfig(EXAMPLE_CAN, TX_MESSAGE_BUFFER_NUM, true);
   
4. #else
   
5.     FLEXCAN_SetTxMbConfig(EXAMPLE_CAN, TX_MESSAGE_BUFFER_NUM, true);
   
6. #endif
   
7. 
   
8.     /* Create FlexCAN handle structure and set call back function. */
   
9.     FLEXCAN_TransferCreateHandle(EXAMPLE_CAN, &flexcanHandle, flexcan_callback, NULL);
   
10. 
    
11.     /* Start receive data through Rx Message Buffer. */
    
12.     rxXfer.mbIdx = (uint8_t)RX_MESSAGE_BUFFER_NUM;
    
13. #if (defined(USE_CANFD) && USE_CANFD)
    
14.     rxXfer.framefd = &rxFrame;
    
15.     (void)FLEXCAN_TransferFDReceiveNonBlocking(EXAMPLE_CAN, &flexcanHandle, &rxXfer);
    
16. #else
    
17.     rxXfer.frame = &rxFrame;
    
18.     (void)FLEXCAN_TransferReceiveNonBlocking(EXAMPLE_CAN, &flexcanHandle, &rxXfer);
    
19. #endif
    
20. 
    
21.     /* Prepare Tx Frame for sending. */
    
22.     txFrame.format = (uint8_t)kFLEXCAN_FrameFormatStandard;
    
23.     txFrame.type   = (uint8_t)kFLEXCAN_FrameTypeData;
    
24.     txFrame.id     = FLEXCAN_ID_STD(0x123);
    
25.     txFrame.length = (uint8_t)DLC;
    
26. #if (defined(USE_CANFD) && USE_CANFD)
    
27.     txFrame.brs = 1U;
    
28. #endif
    
29. #if (defined(USE_CANFD) && USE_CANFD)
    
30.     uint8_t i = 0;
    
31.     for (i = 0; i < DWORD_IN_MB; i++)
    
32.     {
    
33.         txFrame.dataWord[i] = i;
    
34.     }
    
35. #else
    
36.     txFrame.dataWord0 = CAN_WORD0_DATA_BYTE_0(0x11) | CAN_WORD0_DATA_BYTE_1(0x22) | CAN_WORD0_DATA_BYTE_2(0x33) |
    
37.                         CAN_WORD0_DATA_BYTE_3(0x44);
    
38.     txFrame.dataWord1 = CAN_WORD1_DATA_BYTE_4(0x55) | CAN_WORD1_DATA_BYTE_5(0x66) | CAN_WORD1_DATA_BYTE_6(0x77) |
    
39.                         CAN_WORD1_DATA_BYTE_7(0x88);
    
40. #endif
    
41. 
    
42.     SEGGER_RTT_printf(0,"Send message from MB%d to MB%d\r\n", TX_MESSAGE_BUFFER_NUM, RX_MESSAGE_BUFFER_NUM);
    
43. #if (defined(USE_CANFD) && USE_CANFD)
    
44.     for (i = 0; i < DWORD_IN_MB; i++)
    
45.     {
    
46.         SEGGER_RTT_printf(0,"tx word%d = 0x%x\r\n", i, txFrame.dataWord[i]);
    
47.     }
    
48. #else
    
49.     SEGGER_RTT_printf(0,"tx word0 = 0x%x\r\n", txFrame.dataWord0);
    
50.     SEGGER_RTT_printf(0,"tx word1 = 0x%x\r\n", txFrame.dataWord1);
    
51. #endif
    
52. 
    
53.     /* Send data through Tx Message Buffer. */
    
54.     txXfer.mbIdx = (uint8_t)TX_MESSAGE_BUFFER_NUM;
    
55. #if (defined(USE_CANFD) && USE_CANFD)
    
56.     txXfer.framefd = &txFrame;
    
57.     (void)FLEXCAN_TransferFDSendNonBlocking(EXAMPLE_CAN, &flexcanHandle, &txXfer);
    
58. #else
    
59.     txXfer.frame = &txFrame;
    
60.     (void)FLEXCAN_TransferSendNonBlocking(EXAMPLE_CAN, &flexcanHandle, &txXfer);
    
61. #endif
    

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接下来等待发送/接收中断置位相应的Flag:

1.     /* Waiting for Rx Message finish. */
   
2.     while ((!rxComplete) || (!txComplete))
   
3.     {
   
4.     };

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接收到报文后，通过Segger Jlink Viewer打印相关的报文内容。

1.   SEGGER_RTT_printf(0,"EXAMPLE_CAN_CLK_FREQ = %u MHz, CAN BUS bitRate = %uk bps\r\n", EXAMPLE_CAN_CLK_FREQ/1000000, (flexcanConfig.bitRate)/1000);
   
2.                 SEGGER_RTT_printf(0,"rx frame CanID = 0x%x\r\n", (rxFrame.id)>>18);
   
3.     SEGGER_RTT_printf(0,"rx word0 = 0x%x\r\n", rxFrame.dataWord0);
   
4.     SEGGER_RTT_printf(0,"rx word1 = 0x%x\r\n", rxFrame.dataWord1);

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实验结果：


遇到的问题：想要打印一下接收到的报文ID，发现需要进行移位操作后才能得到正确结果。如下所示：

1. SEGGER_RTT_printf(0,"rx frame CanID = 0x%x\r\n", (rxFrame.id)>>18);

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后来在网上检索到类似的问题：NXP Community Decode/Revert CAN Frame ID，贴在这里，以供参考。



参考：
MCUXpresso SDK API Reference Manual https://mcuxpresso.nxp.com/api_doc/dev/71/group__flexcan__driver.html

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