用MATLAB处理多个Slamtec LIDAR连接问题

Question

我遇到了一些初始的LIDAR连接问题，同时使用MATALB连接4个Slamtec A3和这里提供的接口库：https://github.com/ENSTABretagneRobotics/Hardware-MATLAB

问题是，在连接之前，我必须在至少一个LIDARS上重新尝试连接。它也可以随LIDAR而变化，也就是说。也就是说，除了一个LIDAR，所有的LIDAR都是第一次连接。一次，可能是一个COM端口上的LIDAR，另一次可能是另一个COM端口上的LIDAR。

这就是现在设置的方式。基本上，MATALB加载提供的接口库hardwarex.dll。它公开了一些要由MATLAB使用的库方法。

连接LIDAR的方法如下：

1. 打开RS232端口
2. Sets端口选项
3. 获得一些信息和健康状态来自于激光雷达
4. 将马达PWM设置为零(停止激光雷达马达)

H 111使用快速扫描模式选项H 212g 213

在这里的某个地方，通讯会出错。使用串行嗅探器，我能够看到LIDAR在向LIDAR发出以下消息之后出现了错误：

a5 f0 02   ff 03 ab   a5 25   a5 82 05 00 00 00 00 00 22

按照这个顺序，我跟踪到以下库方法：

SetMotorPWMRequestRPLIDAR()
CheckMotorControlSupportRequestRPLIDAR()
StopRequestRPLIDAR()
StartExpressScanRequestRPLIDAR()   <-- Error here

激光雷达对此作出的反应是：

a5 5a 54 00 00 40 82 

作为一个成功的连接响应，来自LIDAR的内容要长得多。

Things我试过

lidar.

• Setting之前和/或之后，
• 耗尽(强制所有写入数据)具有接口库DrainComputerRS232Port()方法的写入缓冲区，TX/ with FIFO缓冲区到FILE_FLAG_NO_BUFFERING (即。WriteFile()).
• Changing硬件FIFO缓冲器最大(16)到最小(1)。
• 使用MATLAB的串行()命令在加载库或尝试connections.

之前刷新任何输入或输出缓冲区。

，这是我使用的系统和设置

Lidar (x4)

• Slamtec RPLIDAR A3
• 固件通过USB (不使用USB集线器)
• 没有连接到

的其他COM端口设备

计算机

• OS: Windows 10 Pro - Build 1903
• CPU: Intel Xeon 3.00Ghz
• RAM: 64 GB
• HD: SSD -512 64

串口设置

256000

• Timeout：
• Boud：

1000

软件

• MATLAB R2018b (9.5.0)

我一直用这个把头撞在墙上。任何帮助都是非常感谢的！

Answer 1

我要自己回答问题。任何人有兴趣进行更详细的讨论，请参阅MATLAB RPLIDAR回购版上的问题：

https://github.com/ENSTABretagneRobotics/Hardware-MATLAB/issues/2

正如我提到的，在调试时，错误似乎发生在ConnectRPLIDAR() --> StartExpressScanRequestRPLIDAR()，然后具体地在这里：

    // Receive the first data response (2 data responses needed for angles computation...).
    memset(pRPLIDAR->esdata_prev, 0, sizeof(pRPLIDAR->esdata_prev));
    if (ReadAllRS232Port(&pRPLIDAR->RS232Port, pRPLIDAR->esdata_prev, sizeof(pRPLIDAR->esdata_prev)) != EXIT_SUCCESS)
    {
        // Failure
        printf("A RPLIDAR is not responding correctly. \n");
        return EXIT_FAILURE;
    }

在此之前发生的事情似乎是在WriteAllRS232Port()中发出命令之后，有时它不会在ReadAllRS232Port()中读取响应，esdata_prev就什么都不是了。

我们尝试在第二个mSleep(500)之前实现一个ReadAllRS232Port()延迟，这似乎很有帮助(我猜激光雷达的响应速度很慢)，但是这个问题并没有得到完全解决。

以下是每次使用4个lidars时使其工作的原因：

inline int StartExpressScanRequestRPLIDAR(RPLIDAR* pRPLIDAR)
{
    unsigned char reqbuf[] = { START_FLAG1_RPLIDAR,EXPRESS_SCAN_REQUEST_RPLIDAR,0x05,0,0,0,0,0,0x22 };
    unsigned char descbuf[7];
    unsigned char sync = 0;
    unsigned char ChkSum = 0;

    // Send request to output/tx OS FIFO buffer for port
    if (WriteAllRS232Port(&pRPLIDAR->RS232Port, reqbuf, sizeof(reqbuf)) != EXIT_SUCCESS)
    {
        printf("Error writing data to a RPLIDAR. \n");
        return EXIT_FAILURE;
    }


    // Receive the response descriptor.
    memset(descbuf, 0, sizeof(descbuf));  // Alocate memory
    if (ReadAllRS232Port(&pRPLIDAR->RS232Port, descbuf, sizeof(descbuf)) != EXIT_SUCCESS)
    {
        printf("A RPLIDAR is not responding correctly. \n");
        return EXIT_FAILURE;
    }


    // Quick check of the response descriptor.
    if ((descbuf[2] != 0x54) || (descbuf[5] != 0x40) || (descbuf[6] != MEASUREMENT_CAPSULED_RESPONSE_RPLIDAR))
    {
        printf("A RPLIDAR is not responding correctly. \n");
        return EXIT_FAILURE;
    }


    // Keep anticipating a port read buffer for 1 second
    int timeout = 1500;

    // Check it every 5 ms
    // Note on Checking Period Value:
    //    Waiting on 82 bytes in lidar payload
    //    10 bits per byte for the serial communication
    //    820 bits / 256000 baud = 0.0032s = 3.2ms
    int checkingperiod = 5;

    RS232PORT* pRS232Port = &pRPLIDAR->RS232Port;
    int i;
    int count = 0;

    // Wait for something to show up on the input buffer on port
    if (!WaitForRS232Port(&pRPLIDAR->RS232Port, timeout, checkingperiod))
    {
        //Success - Something is there

        // If anything is on the input buffer, wait until there is enough
        count = 0;
        for (i = 0; i < 50; i++)
        {
            // Check the input FIFO buffer on the port
            GetFIFOComputerRS232Port(pRS232Port->hDev, &count);

            // Check if there is enough to get a full payload read
            if (count >= sizeof(pRPLIDAR->esdata_prev))
            {
                // Thre is enough, stop waiting
                break;
            }
            else
            {
                // Not enough, wait a little
                mSleep(checkingperiod);
            }
        }

    }
    else
    {
        //Failure - After waiting for an input buffer, it wasn't there
        printf("[StartExpressScanRequestRPLIDAR] : Failed to detect response on the input FIFO buffer. \n");
        return EXIT_FAILURE;
    }


    // Receive the first data response (2 data responses needed for angles computation...).
    memset(pRPLIDAR->esdata_prev, 0, sizeof(pRPLIDAR->esdata_prev));
    if (ReadAllRS232Port(&pRPLIDAR->RS232Port, pRPLIDAR->esdata_prev, sizeof(pRPLIDAR->esdata_prev)) != EXIT_SUCCESS)
    {
        // Failure
        printf("A RPLIDAR is not responding correctly. \n");
        return EXIT_FAILURE;
    }


    // Analyze the first data response.
    sync = (pRPLIDAR->esdata_prev[0] & 0xF0)|(pRPLIDAR->esdata_prev[1]>>4);
    if (sync != START_FLAG1_RPLIDAR)
    { 
        printf("A RPLIDAR is not responding correctly : Bad sync1 or sync2. \n");
        return EXIT_FAILURE;    
    }

    ChkSum = (pRPLIDAR->esdata_prev[1]<<4)|(pRPLIDAR->esdata_prev[0] & 0x0F);
    // Force ComputeChecksumRPLIDAR() to compute until the last byte...
    if (ChkSum != ComputeChecksumRPLIDAR(pRPLIDAR->esdata_prev+2, sizeof(pRPLIDAR->esdata_prev)-1))
    { 
        printf("A RPLIDAR is not responding correctly : Bad ChkSum. \n");
        return EXIT_FAILURE;    
    }

    return EXIT_SUCCESS;
}

因此，在上面的代码中，我们等待操作系统读取FIFO缓冲区在1.5s内显示一些内容，每5ms检查一次(WaitForRS232Port())。如果出现任何情况，请确保等待足够的有效负载(GetFIFOComputerRS232Port())大小。

我不确定它是否起了作用，但我们也删除了OS写FIFO缓冲区，将它从0改为FILE_FLAG_NO_BUFFERING

File: OSComputerRS232Port.h
...
    hDev = CreateFile( 
        tstr,
        GENERIC_READ|GENERIC_WRITE,
        0, // Must be opened with exclusive-access.
        NULL, // No security attributes.
        OPEN_EXISTING, // Must use OPEN_EXISTING.
        FILE_FLAG_NO_BUFFERING, // Not overlapped I/O. Should use FILE_FLAG_WRITE_THROUGH and maybe also FILE_FLAG_NO_BUFFERING?
        NULL // hTemplate must be NULL for comm devices.
        );
...