为什么使用lsusb读取失败？

Question

我需要读取马达控制单元的响应。写入以?开头的命令后，电机单元应响应一些文本。也就是说，在?MSG上，它应该报告其状态。但是，当我尝试读取状态时，单元不发送任何内容，请求以超时结束。

代码非常简单，并且使用libusb。该程序从设备上分离所有活动的驱动程序，将其自身附加到设备上，传输命令?MSG并等待响应。在那之后，它就会分离并结束。

为什么没有响应？代码中是否有任何错误，或者是电机单元的问题？我确信当电机移动时，例如在PSET1=4000上，单元会发送和接收命令

#include <assert.h>
#include <string.h>

#define VENDOR_ID     0x0483
#define PRODUCT_ID    0x5740
#define BULK_EP_IN      0x03
#define BULK_EP_OUT     0x81 // From computer to control unit
#define INTERFACE_IN       0
#define INTERFACE_OUT      1

#define BUF_SIZE    64

int main()
{
    libusb_context *ctx;
    libusb_device_handle *dev_handle;
    int r = 0;
    int actual, length, received;
    char cmd[] = "?MSG\r\n";
    char buffer[BUF_SIZE];
    length = strlen(cmd);
    r = libusb_init(&ctx);
    assert(r == 0);

    /* Set verbosity level to 3, as suggested in the documentation */
    libusb_set_debug(ctx, 3);

    /* Get device handle */
    dev_handle = libusb_open_device_with_vid_pid(ctx, VENDOR_ID, PRODUCT_ID);
    assert(dev_handle != NULL);

    /* Find out if kernel driver is attached on IN iface */
    if(libusb_kernel_driver_active(dev_handle, INTERFACE_IN) == 1) {
        printf("Kernel Driver Active\n");
        assert(libusb_detach_kernel_driver(dev_handle, INTERFACE_IN) == 0);
        printf("Kernel Driver Detached!\n");
    }
    if(libusb_kernel_driver_active(dev_handle, INTERFACE_OUT) == 1) {
        printf("Kernel Driver Active\n");
        assert(libusb_detach_kernel_driver(dev_handle, INTERFACE_OUT) == 0);
        printf("Kernel Driver Detached!\n");
    }

    /* Claim IN interface of device */
    r = libusb_claim_interface(dev_handle, INTERFACE_IN);
    assert(r >= 0);
    /* claim OUT interface of device */
    r = libusb_claim_interface(dev_handle, INTERFACE_OUT);
    assert(r >= 0);


    /* Transfer commands */
    r = libusb_bulk_transfer(dev_handle, BULK_EP_IN, (unsigned char *)cmd, length, &actual, 0);
    assert(r == 0 && actual > 0 && actual == length);
    printf("Written %s\n",cmd);

    /* Now read response */
    if (cmd[0] == '?') {
        char buffer[BUF_SIZE] = "";
        int received = 0;
        do {
            int i;
            r = libusb_bulk_transfer(dev_handle, BULK_EP_OUT, (unsigned char *)buffer, BUF_SIZE, &received, 1000);
            if(r == LIBUSB_ERROR_TIMEOUT) {
                printf("Timeout\n");
            } else {
                assert(r == 0);
            }
            for(i = 0; i<BUF_SIZE;i++)
                printf("%c",buffer[i]);
        } while (received != 0);
    }

    /* Release devices */
    r = libusb_release_interface(dev_handle, INTERFACE_IN);
    assert(r == 0);
    r = libusb_release_interface(dev_handle, INTERFACE_OUT);
    assert(r == 0);

    /* Clean */
    libusb_close(dev_handle);
    libusb_exit(ctx);
}

以下是sudo lsusb --verbose设备的描述，以防它很重要：

Bus 003 Device 003: ID 0483:5740 STMicroelectronics STM32F407
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            2 Communications
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0x0483 STMicroelectronics
  idProduct          0x5740 STM32F407
  bcdDevice            1.00
  iManufacturer           1 STMicroelectronics
  iProduct                2 STR75x Virtual COM Port
  iSerial                 3 Demo 1.000
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           67
    bNumInterfaces          2
    bConfigurationValue     1
    iConfiguration          0
    bmAttributes         0xc0
      Self Powered
    MaxPower                0mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           1
      bInterfaceClass         2 Communications
      bInterfaceSubClass      2 Abstract (modem)
      bInterfaceProtocol      1 AT-commands (v.25ter)
      iInterface              0
      CDC Header:
        bcdCDC               1.10
      CDC Call Management:
        bmCapabilities       0x00
        bDataInterface          1
      CDC ACM:
        bmCapabilities       0x02
          line coding and serial state
      CDC Union:
        bMasterInterface        0
        bSlaveInterface         1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0008  1x 8 bytes
        bInterval             255
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass        10 CDC Data
      bInterfaceSubClass      0 Unused
      bInterfaceProtocol      0
      iInterface              0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
Device Status:     0x0001
  Self Powered

Answer 1

您可以通过RS-232协议与设备通信，因为它提供了一个虚拟COM端口，这是一个CDC ACM类。内核驱动程序是cdc_acm。

  iManufacturer           1 STMicroelectronics
  iProduct                2 STR75x Virtual COM Port
  bInterfaceClass         2 Communications
  bInterfaceSubClass      2 Abstract (modem)
  bInterfaceProtocol      1 AT-commands (v.25ter)
  iInterface              0
  CDC Header:
    bcdCDC               1.10
  CDC Call Management:
    bmCapabilities       0x00
    bDataInterface          1
  CDC ACM:
    bmCapabilities       0x02
      line coding and serial state
  CDC Union:
    bMasterInterface        0
    bSlaveInterface         1

因此，您可以通过向/dev/ttyACMx (或/dev/ttyUSBx)发送RS-232命令来与设备通信(将x替换为系统上的数字)

要检查这一点，您可以使用像，... 这样的终端程序。您必须确定正确的COM端口设置(波特率、奇偶校验、开始/停止位等)。

有几个RS-232库，请参阅

检查设备中插件之后的dmesg输出，以了解使用的是哪个驱动程序。