libusb学习笔记1——libusb的安装

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libusb的用处蛮多的，libusb从入门开始学起，也是作为学习开源库的一点经验。

libusb的安装网络上大把的，这里为了先熟悉库，采用了偷懒的办法：直接apt-get install .

直接在终端输入：

sudo apt-get install libusb-dev

sudo apt-get install libusb-1.0-0-dev

完成后，新建一个C文件：

#include <unistd.h>#include <stdio.h>#include <libusb-1.0/libusb.h>// First, use "lsusb" see vid and pid.// there is my printer(hp deskjet 1010) vid and pid.#define VID 0x05e3#define PID 0x0723static int device_satus(libusb_device_handle *hd){int interface = 0;unsigned char byte;libusb_control_transfer(hd, LIBUSB_ENDPOINT_IN | LIBUSB_REQUEST_TYPE_CLASS | LIBUSB_RECIPIENT_INTERFACE,LIBUSB_REQUEST_CLEAR_FEATURE,0,interface,&byte, 1, 5000);printf("status:0x%x\n", byte);/** * byte * normal:0x18 * other :0x10 */return 0;}int main() {libusb_device **devs; //pointer to pointer of device, used to retrieve a list of deviceslibusb_device_handle *dev_handle; //a device handlelibusb_context *ctx = NULL; //a libusb sessionint r; //for return valuesssize_t cnt; //holding number of devices in listr = libusb_init(&ctx); //initialize the library for the session we just declaredif(r < 0) {perror("Init Error\n"); //there was an errorreturn 1;}libusb_set_debug(ctx, LIBUSB_LOG_LEVEL_INFO); //set verbosity level to 3, as suggested in the documentationcnt = libusb_get_device_list(ctx, &devs); //get the list of devicesif(cnt < 0) {perror("Get Device Error\n"); //there was an errorreturn 1;}printf("%d Devices in list.\n", cnt);dev_handle = libusb_open_device_with_vid_pid(ctx, VID, PID); //these are vendorID and productID I found for my usb deviceif(dev_handle == NULL)perror("Cannot open device\n");elseprintf("Device Opened\n");libusb_free_device_list(devs, 1); //free the list, unref the devices in itif(libusb_kernel_driver_active(dev_handle, 0) == 1) { //find out if kernel driver is attachedprintf("Kernel Driver Active\n");if(libusb_detach_kernel_driver(dev_handle, 0) == 0) //detach itprintf("Kernel Driver Detached!\n");}r = libusb_claim_interface(dev_handle, 0); //claim interface 0 (the first) of device (mine had jsut 1)if(r < 0) {perror("Cannot Claim Interface\n");return 1;}printf("Claimed Interface\n");device_satus(dev_handle);libusb_close(dev_handle); //close the device we openedlibusb_exit(ctx); //needs to be called to end thereturn 0;}

注意上述代码中的VID和PID分别是制造商和产品ID：可以通过

cd /sys/kernel/debugcat usb/devices

Ubuntu上输出如下：

T:  Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#=  7 Spd=480  MxCh= 0D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1P:  Vendor=05e3 ProdID=0723 Rev=94.51S:  Manufacturer=Generic S:  Product=USB StorageS:  SerialNumber=000000009451C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=500mAI:* If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storageE:  Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0msE:  Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms

第三行的P：

Vendor就是VID， ProdID就是PID

P:  Vendor=05e3 ProdID=0723

修正代码中的VID和PID就可以编译了。

注意编译的时候需要链接库 -lusb-1.0：

gcc usb.c -lusb-1.0

运行时需要以root权限运行，否则会出现无权限的错误。

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