Gadget应用实例之serial
Gadget应用实例之serial
文章目录
- Gadget应用实例之serial
- 参考资料：
-
- 一、编写程序
-
- 1.1 编程思路
- 1.2 zero设备的描述符
- 1.3 编程
- 二、 上机实验
- 致谢
参考资料：
- https://blog.csdn.net/embededswordman/article/details/6689593
- Linux文档：Documentation\usb\gadget_serial.txt
一、编写程序
1.1 编程思路
涉及的程序如下图所示：
基于libusb编写程序：
- 找到设备
- 选择配置：loopback、sourcesink
- 得到端点：找到interface进而得到endpoint
- 读写数据：操作endpoint
1.2 zero设备的描述符
在Ubuntu里执行如下命令：
$ lsusb -v -d 0525:a4a0
可以列出zero设备的描述符：
Bus 001 Device 002: ID 0525:a4a0 Netchip Technology, Inc. Linux-USB "Gadget Zero"
Couldn't open device, some information will be missing
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 255 Vendor Specific Class
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x0525 Netchip Technology, Inc.
idProduct 0xa4a0 Linux-USB "Gadget Zero"
bcdDevice 4.09
iManufacturer 1
iProduct 2
iSerial 3
bNumConfigurations 2
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 69
bNumInterfaces 1
bConfigurationValue 3
iConfiguration 4
bmAttributes 0xc0
Self Powered
MaxPower 2mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 1
bNumEndpoints 4
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 1
Transfer Type Isochronous
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 4
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 1
Transfer Type Isochronous
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 4
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 32
bNumInterfaces 1
bConfigurationValue 2
iConfiguration 5
bmAttributes 0xc0
Self Powered
MaxPower 2mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 255 Vendor Specific Class
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 6
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
它有2个配置：
- 第1个配置(bConfigurationValue = 2)对应loopback功能：里面有1个接口，接口有1个setting，下面有2个endpoint
- 第2个配置(bConfigurationValue = 3)对应SourceSink功能：里面有1个接口，接口有2个setting
- 第1个setting下面有2个endpoint：都是bulk端点
- 第2个setting下面有4个endpoint：2个是bulk端点，另外2个是Isochronous端点
1.3 编程
参考libusb示例：libusb\examples\xusb.c
zero_app.c
#include : select config\n" , name);
printf("%s -wstr : write string\n" , name);
printf("%s -rstr : read string\n", name);
printf("%s -w : write bytes\n" , name);
printf("%s -r : read 32 bytes\n", name);
}
int main(int argc, char **argv)
{
int err = 0;
libusb_device *dev, **devs;
int num_devices;
int endpoint;
int interface_num = 0;
int found = 0;
int transferred;
int count = 0;
unsigned char buffer[1024];
struct libusb_config_descriptor *config_desc;
struct libusb_device_handle *dev_handle = NULL;
int i;
int in_ep, out_ep;
int in_ep_maxlen;
if (argc == 1)
{
PrintUsage(argv[0]);
return 0;
}
/* libusb_init */
err = libusb_init(NULL);
if (err < 0) {
fprintf(stderr, "failed to initialise libusb %d - %s\n", err, libusb_strerror(err));
exit(1);
}
/* open device */
dev_handle = libusb_open_device_with_vid_pid(NULL, DRIVER_VENDOR_NUM, DRIVER_PRODUCT_NUM);
if (!dev_handle) {
printf("can not open zero device\n");
return -1;
}
dev = libusb_get_device(dev_handle);
/* 想选择某一个配置, 先知道它的bConfigurationValue */
if (!strcmp(argv[1], "-l"))
{
for (i = 0; i < 255; i++)
{
/* parse interface descriptor, find usb mouse */
err = libusb_get_config_descriptor(dev, i, &config_desc);
if (err) {
//fprintf(stderr, "could not get configuration descriptor\n");
break;
}
printf("config %d: bConfigurationValue = %d\n", i, config_desc->bConfigurationValue);
libusb_free_config_descriptor(config_desc);
}
return 0;
}
/* 想选择某一个配置 */
if (!strcmp(argv[1], "-s") && (argc == 3))
{
i = strtoul(argv[2], NULL, 0);
libusb_set_auto_detach_kernel_driver(dev_handle, 0);
libusb_detach_kernel_driver(dev_handle, 0);
//libusb_release_interface(dev_handle, 0);
err = libusb_set_configuration(dev_handle, i);
if (err) {
fprintf(stderr, "could not set configuration as %d, err = %d\n", i, err);
return -1;
}
return 0;
}
err = libusb_get_configuration(dev_handle, &i);
fprintf(stdout, "current config: %d\n", i);
/* 想读写数据需要得到endpoint */
err = get_bulk_endpoint(dev, &in_ep, &out_ep, &in_ep_maxlen);
if (err) {
fprintf(stderr, "could not get bulk endpoints\n");
goto exit;
}
fprintf(stdout, "in_ep = 0x%x, out_ep = 0x%x\n", in_ep, out_ep);
/* 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_interface\n");
goto exit;
}
/* write string */
if (!strcmp(argv[1], "-wstr") && (argc == 3))
{
memset(buffer, 0, 32);
strncpy(buffer, argv[2], 32);
err = libusb_bulk_transfer(dev_handle, out_ep,
buffer, 32, &transferred, 1000);
if (err) {
fprintf(stderr, "libusb_bulk_transfer err = %d\n", err);
goto exit;
}
if (transferred != 32)
{
fprintf(stderr, "transferred != 32\n");
}
goto exit;
}
/* read string */
if (!strcmp(argv[1], "-rstr"))
{
memset(buffer, 0, 32);
err = libusb_bulk_transfer(dev_handle, in_ep,
buffer, 32, &transferred, 1000);
if (err) {
fprintf(stderr, "libusb_bulk_transfer err = %d\n", err);
goto exit;
}
if (transferred != 32)
{
fprintf(stderr, "transferred != 32\n");
}
printf("Read string: %s\n", buffer);
goto exit;
}
/* write datas */
if (!strcmp(argv[1], "-w") && (argc >= 3))
{
memset(buffer, 0, 32);
/* argv[2],... */
for (i = 2; i < argc; i++)
buffer[i-2] = strtoul(argv[i], NULL, 0);
err = libusb_bulk_transfer(dev_handle, out_ep,
buffer, argc - 2, &transferred, 1000);
if (err) {
fprintf(stderr, "libusb_bulk_transfer err = %d\n", err);
goto exit;
}
if (transferred != argc - 2)
{
fprintf(stderr, "transferred != %d\n", argc - 2);
}
goto exit;
}
/* read datas */
if (!strcmp(argv[1], "-r")) /* 读Source/Sink这个配置里的端点时, 它一次性返回512字节的数据 */
{
memset(buffer, 0, 1024);
err = libusb_bulk_transfer(dev_handle, in_ep,
buffer, in_ep_maxlen, &transferred, 1000);
if (err) {
fprintf(stderr, "libusb_bulk_transfer err = %d\n", err);
goto exit;
}
if (transferred != in_ep_maxlen)
{
fprintf(stderr, "transferred != in_ep_maxlen\n");
}
printf("Read datas: \n");
for (i = 0; i < transferred; i++)
{
printf("%02x ", buffer[i]);
if ((i+1) % 16 == 0)
printf("\n");
}
printf("\n");
goto exit;
}
exit:
/* libusb_close */
libusb_release_interface(dev_handle, interface_num);
libusb_close(dev_handle);
libusb_exit(NULL);
return err;
}
二、 上机实验
实验步骤：
-
先安装g_zero驱动程序：在开发板上执行
modprobe g_zero -
然后连接OTG线到PC
-
在Ubuntu中识别出设备
-
执行测试程序
-
先编译：在Ubuntu里执行如下命令
apt-cache search libusb # 查找libusb开发包 sudo apt install libusb-1.0-0-dev # 安装libusb开发包 gcc -o zero_app zero_app.c -lusb-1.0 # 编译 -
测试：在Ubuntu里执行如下命令
$ sudo ./zero_app -l # 列出设备的配置值 config 0: bConfigurationValue = 3 config 1: bConfigurationValue = 2 # 测试loopback功能 $ sudo ./zero_app -s 2 # 选择loopback的配置 $ sudo ./zero_app -wstr www.100ask.net # 写入字符串 current config: 2 in_ep = 0x81, out_ep = 0x1 $ sudo ./zero_app -rstr # 读出字符串 current config: 2 in_ep = 0x81, out_ep = 0x1 Read string: www.100ask.net $ sudo ./zero_app -w 1 2 3 4 5 6 7 8 # 写入8个字节 current config: 2 in_ep = 0x81, out_ep = 0x1 sudo ./zero_app -r # 读到8个字节 current config: 2 in_ep = 0x81, out_ep = 0x1 transferred != in_ep_maxlen Read datas: 01 02 03 04 05 06 07 08 #测试Source/Sink功能 $ sudo ./zero_app -s 3 # 选择source/sink的配置 [email protected]:/work/nfs_rootfs/libusb_zero$ sudo ./zero_app -r # 读数据 current config: 3 in_ep = 0x81, out_ep = 0x1 Read datas: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 sudo ./zero_app -w 0 0 0 # 写数据, 只能写入0, # 写入其他值将会导致开发板上的驱动认为是错误然后halt out端点 # 然后只能重新执行 ”sudo ./zero_app -s 3“ 才能恢复
-
致谢
以上笔记源自
韦东山老师的视频课程，感谢韦老师,韦老师是嵌入式培训界一股清流，为嵌入式linux开发点起的星星之火，也愿韦老师桃李满园。聚是一团火，散是满天星！
在这样一个速食的时代，坚持做自己，慢下来，潜心琢磨，心怀敬畏，领悟知识，才能向下扎到根，向上捅破天，背着世界往前行！
仅此向嵌入行业里的每一个认真做技术的从业者致敬！