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IMX6ULL/doc_pic/12_USB/13_Gadget应用实例之serial.md
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IMX6ULL/doc_pic/12_USB/13_Gadget应用实例之serial.md
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# Gadget应用实例之serial #
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参考资料：
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* https://blog.csdn.net/embededswordman/article/details/6689593
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* Linux文档：Documentation\usb\gadget_serial.txt
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*
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## 1. 编写程序
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### 1.1 编程思路
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涉及的程序如下图所示：
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基于libusb编写程序：
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* 找到设备
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* 选择配置：loopback、sourcesink
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* 得到端点：找到interface进而得到endpoint
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* 读写数据：操作endpoint
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### 1.2 zero设备的描述符
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在Ubuntu里执行如下命令：
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```shell
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$ lsusb -v -d 0525:a4a0
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```
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可以列出zero设备的描述符：
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```shell
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Bus 001 Device 002: ID 0525:a4a0 Netchip Technology, Inc. Linux-USB "Gadget Zero"
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Couldn't open device, some information will be missing
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Device Descriptor:
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bLength 18
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bDescriptorType 1
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bcdUSB 2.00
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bDeviceClass 255 Vendor Specific Class
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bDeviceSubClass 0
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bDeviceProtocol 0
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bMaxPacketSize0 64
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idVendor 0x0525 Netchip Technology, Inc.
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idProduct 0xa4a0 Linux-USB "Gadget Zero"
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bcdDevice 4.09
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iManufacturer 1
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iProduct 2
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iSerial 3
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bNumConfigurations 2
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Configuration Descriptor:
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bLength 9
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bDescriptorType 2
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wTotalLength 69
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bNumInterfaces 1
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bConfigurationValue 3
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iConfiguration 4
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bmAttributes 0xc0
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Self Powered
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MaxPower 2mA
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Interface Descriptor:
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bLength 9
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bDescriptorType 4
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bInterfaceNumber 0
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bAlternateSetting 0
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bNumEndpoints 2
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bInterfaceClass 255 Vendor Specific Class
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bInterfaceSubClass 0
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bInterfaceProtocol 0
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iInterface 0
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Endpoint Descriptor:
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bLength 7
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bDescriptorType 5
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bEndpointAddress 0x81 EP 1 IN
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bmAttributes 2
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Transfer Type Bulk
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Synch Type None
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Usage Type Data
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wMaxPacketSize 0x0200 1x 512 bytes
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bInterval 0
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Endpoint Descriptor:
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bLength 7
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bDescriptorType 5
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bEndpointAddress 0x01 EP 1 OUT
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bmAttributes 2
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Transfer Type Bulk
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Synch Type None
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Usage Type Data
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wMaxPacketSize 0x0200 1x 512 bytes
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bInterval 0
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Interface Descriptor:
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bLength 9
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bDescriptorType 4
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bInterfaceNumber 0
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bAlternateSetting 1
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bNumEndpoints 4
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bInterfaceClass 255 Vendor Specific Class
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bInterfaceSubClass 0
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bInterfaceProtocol 0
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iInterface 0
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Endpoint Descriptor:
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bLength 7
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bDescriptorType 5
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bEndpointAddress 0x81 EP 1 IN
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bmAttributes 2
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Transfer Type Bulk
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Synch Type None
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Usage Type Data
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wMaxPacketSize 0x0200 1x 512 bytes
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bInterval 0
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Endpoint Descriptor:
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bLength 7
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bDescriptorType 5
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bEndpointAddress 0x01 EP 1 OUT
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bmAttributes 2
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Transfer Type Bulk
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Synch Type None
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Usage Type Data
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wMaxPacketSize 0x0200 1x 512 bytes
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bInterval 0
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Endpoint Descriptor:
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bLength 7
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bDescriptorType 5
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bEndpointAddress 0x82 EP 2 IN
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bmAttributes 1
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Transfer Type Isochronous
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Synch Type None
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Usage Type Data
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wMaxPacketSize 0x0400 1x 1024 bytes
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bInterval 4
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Endpoint Descriptor:
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bLength 7
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bDescriptorType 5
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bEndpointAddress 0x02 EP 2 OUT
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bmAttributes 1
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Transfer Type Isochronous
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Synch Type None
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Usage Type Data
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wMaxPacketSize 0x0400 1x 1024 bytes
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bInterval 4
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Configuration Descriptor:
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bLength 9
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bDescriptorType 2
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wTotalLength 32
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bNumInterfaces 1
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bConfigurationValue 2
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iConfiguration 5
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bmAttributes 0xc0
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Self Powered
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MaxPower 2mA
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Interface Descriptor:
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bLength 9
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bDescriptorType 4
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bInterfaceNumber 0
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bAlternateSetting 0
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bNumEndpoints 2
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bInterfaceClass 255 Vendor Specific Class
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bInterfaceSubClass 0
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bInterfaceProtocol 0
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iInterface 6
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Endpoint Descriptor:
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bLength 7
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bDescriptorType 5
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bEndpointAddress 0x81 EP 1 IN
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bmAttributes 2
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Transfer Type Bulk
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Synch Type None
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Usage Type Data
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wMaxPacketSize 0x0200 1x 512 bytes
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bInterval 0
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Endpoint Descriptor:
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bLength 7
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bDescriptorType 5
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bEndpointAddress 0x01 EP 1 OUT
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bmAttributes 2
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Transfer Type Bulk
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Synch Type None
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Usage Type Data
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wMaxPacketSize 0x0200 1x 512 bytes
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bInterval 0
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```
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它有2个配置：
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* 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
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* 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
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* 第1个setting下面有2个endpoint：都是bulk端点
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* 第2个setting下面有4个endpoint：2个是bulk端点，另外2个是Isochronous端点
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### 1.3 编程
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参考libusb示例：libusb\examples\xusb.c
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## 2. 上机实验
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实验步骤：
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* 先安装g_zero驱动程序：在开发板上执行`modprobe g_zero`
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* 然后连接OTG线到PC
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* 在Ubuntu中识别出设备
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* 执行测试程序
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* 先编译：在Ubuntu里执行如下命令
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```shell
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apt-cache search libusb # 查找libusb开发包
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sudo apt install libusb-1.0-0-dev # 安装libusb开发包
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gcc -o zero_app zero_app.c -lusb-1.0 # 编译
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```
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* 测试：在Ubuntu里执行如下命令
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```shell
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$ sudo ./zero_app -l # 列出设备的配置值
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config 0: bConfigurationValue = 3
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config 1: bConfigurationValue = 2
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# 测试loopback功能
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$ sudo ./zero_app -s 2 # 选择loopback的配置
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$ sudo ./zero_app -wstr www.100ask.net # 写入字符串
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current config: 2
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in_ep = 0x81, out_ep = 0x1
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$ sudo ./zero_app -rstr # 读出字符串
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current config: 2
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in_ep = 0x81, out_ep = 0x1
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Read string: www.100ask.net
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$ sudo ./zero_app -w 1 2 3 4 5 6 7 8 # 写入8个字节
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current config: 2
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in_ep = 0x81, out_ep = 0x1
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sudo ./zero_app -r # 读到8个字节
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current config: 2
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in_ep = 0x81, out_ep = 0x1
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transferred != in_ep_maxlen
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Read datas:
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01 02 03 04 05 06 07 08
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#测试Source/Sink功能
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$ sudo ./zero_app -s 3 # 选择source/sink的配置
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book@100ask:~/nfs_rootfs/05_libusb_zero$ sudo ./zero_app -r # 读数据
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current config: 3
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in_ep = 0x81, out_ep = 0x1
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Read datas:
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00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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sudo ./zero_app -w 0 0 0 # 写数据, 只能写入0,
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# 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
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# 然后只能重新执行 ”sudo ./zero_app -s 3“ 才能恢复
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```
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