使用同步接口读取鼠标数据的方法

编写源码

#include < errno.h >
#include < signal.h >
#include < stdio.h >
#include < stdlib.h >
#include < string.h >

#include < libusb-1.0/libusb.h >

int main(int argc, char **argv)
{
    int err;
    libusb_device *dev, **devs;
    int num_devices;
    int endpoint;
    int interface_num;
    int found = 0;
    int transferred;
    int count = 0;
    unsigned char buffer[16];
    struct libusb_config_descriptor *config_desc;
    struct libusb_device_handle *dev_handle = NULL;
    
    /* libusb_init */
    err = libusb_init(NULL);
    if (err < 0) {
        fprintf(stderr, "failed to initialise libusb %d - %sn", err, libusb_strerror(err));
        exit(1);
    }

    /* get device list */
    if ((num_devices = libusb_get_device_list(NULL, &devs)) < 0) {
        fprintf(stderr, "libusb_get_device_list() failedn");
        libusb_exit(NULL);
        exit(1);
    }
    fprintf(stdout, "libusb_get_device_list() okn");

    /* for each device, get config descriptor */
    for (int i = 0; i < num_devices; i++) {
        dev = devs[i];

        /* parse interface descriptor, find usb mouse */        
        err = libusb_get_config_descriptor(dev, 0, &config_desc);
        if (err) {
            fprintf(stderr, "could not get configuration descriptorn");
            continue;
        }
        fprintf(stdout, "libusb_get_config_descriptor() okn");

        for (int interface = 0; interface < config_desc- >bNumInterfaces; interface++) {
            const struct libusb_interface_descriptor *intf_desc = &config_desc- >interface[interface].altsetting[0];
            interface_num = intf_desc- >bInterfaceNumber;

            if (intf_desc- >bInterfaceClass != 3 || intf_desc- >bInterfaceProtocol != 2)
                continue;
            else
            {
                /* 找到了USB鼠标 */
                fprintf(stdout, "find usb mouse okn");
                for (int ep = 0; ep < intf_desc- >bNumEndpoints; ep++)
                {
                    if ((intf_desc- >endpoint[ep].bmAttributes & 3) == LIBUSB_TRANSFER_TYPE_INTERRUPT ||
                            (intf_desc- >endpoint[ep].bEndpointAddress & 0x80) == LIBUSB_ENDPOINT_IN) {
                        /* 找到了输入的中断端点 */
                        fprintf(stdout, "find in int endpointn");
                        endpoint = intf_desc- >endpoint[ep].bEndpointAddress;
                        found = 1;
                        break;
                    }
                    
                }
            }

            if (found)
                break;
        }

        libusb_free_config_descriptor(config_desc);
        
        if (found)
            break;        
    }

    if (!found)
    {
        /* free device list */
        libusb_free_device_list(devs, 1);
        libusb_exit(NULL);
        exit(1);
    }

    if (found)
    {
        /* libusb_open */
        err = libusb_open(dev, &dev_handle);
        if (err)
        {
            fprintf(stderr, "failed to open usb mousen");
            exit(1);
        }
        fprintf(stdout, "libusb_open okn");
    }

    /* free device list */
    libusb_free_device_list(devs, 1);

    /* claim interface */
    libusb_set_auto_detach_kernel_driver(dev_handle, 1);  
    err = libusb_claim_interface(dev_handle, interface_num);
    if (err)
    {
        fprintf(stderr, "failed to libusb_claim_interfacen");
        exit(1);
    }
    fprintf(stdout, "libusb_claim_interface okn");

    /* libusb_interrupt_transfer */
    while (1)
    {
        err = libusb_interrupt_transfer(dev_handle, endpoint, buffer, 16, &transferred, 5000);
        if (!err) {
            /* parser data */
            printf("%04d datas: ", count++);
            for (int i = 0; i < transferred; i++)
            {
                printf("%02x ", buffer[i]);
            }
            printf("n");
        } else if (err == LIBUSB_ERROR_TIMEOUT){
            fprintf(stderr, "libusb_interrupt_transfer timoutn");
        } else {
            fprintf(stderr, "libusb_interrupt_transfer err : %dn", err);
            //exit(1);
        }
        
    }

    /* libusb_close */
    libusb_release_interface(dev_handle, interface_num);
    libusb_close(dev_handle);
    libusb_exit(NULL);
}

2.2 上机实验

2.2.1 在 Ubuntu 上实验

// 1. 安装开发包
$ sudo apt install libusb-1.0-0-dev
    
// 2. 修改源码，包含libusb.h 头文件时用如下代码
#include < libusb-1.0/libusb.h >

// 3. 编译程序指定库
gcc -o readmouse readmouse.c -lusb-1.0

2.2.2 在 IMX6ULL 开发板上实验

• 交叉编译 libusb

  sudo apt-get install libtool
  
  unzip libusb-1.0.26.zip
  cd libusb-1.0.26
  ./autogen.sh
  
  ./configure --host=arm-buildroot-linux-gnueabihf --prefix=$PWD/tmp
  
  make
  
  make install
  
  ls tmp/
  include  lib
  

• 安装库、头文件到工具链的目录里

  libusb-1.0.26/tmp/lib$ cp * -rfd /home/book/100ask_imx6ull-sdk/ToolChain/arm-buildroot-linux-gnueabihf_sdk-buildroot/arm-buildroot-linux-gnueabihf/sysroot/usr/lib/
  
  libusb-1.0.26/tmp/include$ cp libusb-1.0 -rf /home/book/100ask_imx6ull-sdk/ToolChain/arm-buildroot-linux-gnueabihf_sdk-buildroot/arm-buildroot-linux-gnueabihf/sysroot/usr/include/
  

• 交叉编译 app

  arm-buildroot-linux-gnueabihf-gcc -o  readmouse.c -lusb-1.0
  

• 在开发板上插入 USB 鼠标，执行命令

  ./readmouse