usb_desc.c 提供了设备、端点、接口、字符串、群组、制造商描述符。因为joystick是HID设备，所以多了报告描述符。我加了一些注释如下。我的目标是先搞懂其大致的结构，至于细节可以慢慢再学习。
/* USB Standard Device Descriptor 设备描述符*/
const u8 Joystick_DeviceDescriptor[JOYSTICK_SIZ_DEVICE_DESC] =
{
0x12, /*bLength Byte0: the length of bytes is 0x12*/
USB_DEVICE_DESCRIPTOR_TYPE, /*Byte1: 0x01, type of descriptor:Device bDescriptorType*/
0x00, /*bcdUSB compatible with USB2.0 */
0x02, /* 0x00,0x01 means compatible with USB1.0 */
0x00, /*bDeviceClass 群组码*/
0x00, /*bDeviceSubClass 设备次群组*/
0x00, /*bDeviceProtocol 0表示无特定设备协议*/
0x40, /*bMaxPacketSize 最大封包0x40*/
0x83, /*idVendor 制造商ID(0x0483)*/
0x04,
0x10, /*idProduct 产品ID 0x5710*/
0x57,
0x00, /*bcdDevice rel. 2.00 以BCD表示设备发行序号*/
0x02,
1, /*Index of string descriptor describing
manufacturer */
2, /*Index of string descriptor describing
product*/
3, /*Index of string descriptor describing the
device serial number */
0x01 /*bNumConfigurations 配置数目为1，接下来只有1个配置描述符*/
}
; /* Joystick_DeviceDescriptor */
/* USB Configuration Descriptor 配置，接口，端点，群组，制作商描述符*/
/* All Descriptors (Configuration, Interface, Endpoint, Class, Vendor */
const u8 Joystick_ConfigDescriptor[JOYSTICK_SIZ_CONFIG_DESC] =
{
0x09, /* bLength: Configuation Descriptor size 配置描述符 长度为9字节*/
USB_CONFIGURATION_DESCRIPTOR_TYPE, /* bDescriptorType: Configuration */
JOYSTICK_SIZ_CONFIG_DESC, //JOYSTICK_SIZ_CONFIG_DESC 34
0x00, //34=09+09+09+07
/* 34 0x00 总长度为0x34字节，包括配置，接口，端点，bytes与群组描述符。
注意低字节在前。wTotalLength: Bytes returned */
0x01, /*bNumInterfaces: 1 interface，因此接下来只有1个接口描述符*/
0x01, /*bConfigurationValue: Configuration value 接口配置值*/
0x00, /*iConfiguration: Index of string descriptor describing
the configuration*/
0xC0, /*bmAttributes: self powered */
0x32, /*MaxPower 100 mA: this current is used for detecting Vbus*/
/************** Descriptor of Joystick Mouse interface ****************/
/* 09 接口描述符*/
0x09, /*bLength: Interface Descriptor size*/
USB_INTERFACE_DESCRIPTOR_TYPE,/*0x04, 代表接口 bDescriptorType: Interface descriptor type*/
0x00, /*bInterfaceNumber: Number of Interface，接口数目以0为基值*/
0x00, /*bAlternateSetting: Alternate setting 交互设置值*/
0x01, /*bNumEndpoints 端点数目1*/
0x03, /*bInterfaceClass: 群组类型：HID*/
0x01, /*bInterfaceSubClass : 1=BOOT, 0=no boot*/
0x02, /*nInterfaceProtocol : 0=none, 1=keyboard, 2=mouse*/
0, /*iInterface: Index of string descriptor 0个字符串描述符*/
/******************** Descriptor of Joystick Mouse HID **********/
/* 18 */ //群组描述符
0x09, /*bLength: HID Descriptor size*/
HID_DESCRIPTOR_TYPE, /*bDescriptorType: HID*/
0x00,
0x01, /*bcdHID: HID Class Spec release number*/
0x00, /*bCountryCode: Hardware target country，无区域为0*/
0x01, /*bNumDescriptors: Number of HID class descriptors to follow，至少为1*/
0x22, /*bDescriptorType，描述符类型为报告*/
JOYSTICK_SIZ_REPORT_DESC,/*wItemLength: Total length of Report descriptor报告描述符的长度*/
0x00,
/******************** Descriptor of Joystick Mouse endpoint ********************/
/* 27 */ //端点描述符
0x07, /*bLength: Endpoint Descriptor size*/
USB_ENDPOINT_DESCRIPTOR_TYPE, /*bDescriptorType:*/
0x81, /*bEndpointAddress: Endpoint Address (IN) bit0 为1表示IN，端点地址*/
0x03, /*bmAttributes: Interrupt endpoint 中断传输*/
//0 控制；1 等时 2 批量 3 中断
0x04, /*wMaxPacketSize: 4 Byte max */
0x00,
0x20, /*bInterval: Polling Interval (32 ms) 以ms为单位，查询间隔*/
//USB的中断并非一般意义的中断，而是查询
/* 34 */
}
; /* MOUSE_ConfigDescriptor 报告描述符*/
const u8 Joystick_ReportDescriptor[JOYSTICK_SIZ_REPORT_DESC] =
{
0x05, /*Usage Page(Generic Desktop)*/
0x01,
0x09, /*Usage(Mouse)*/
0x02,
0xA1, /*Collection(Logical)*/
0x01,
0x09, /*Usage(Pointer)*/
0x01,
/* 8 */
0xA1, /*Collection(Linked)*/
0x00,
0x05, /*Usage Page(Buttons)*/
0x09,
0x19, /*Usage Minimum(1)*/
0x01,
0x29, /*Usage Maximum(3)*/
0x03,
/* 16 */
0x15, /*Logical Minimum(0)*/
0x00,
0x25, /*Logical Maximum(1)*/
0x01,
0x95, /*Report Count(3)*/
0x03,
0x75, /*Report Size(1)*/
0x01,
/* 24 */
0x81, /*Input(Variable)*/
0x02,
0x95, /*Report Count(1)*/
0x01,
0x75, /*Report Size(5)*/
0x05,
0x81, /*Input(Constant,Array)*/
0x01,
/* 32 */
0x05, /*Usage Page(Generic Desktop)*/
0x01,
0x09, /*Usage(X axis)*/
0x30,
0x09, /*Usage(Y axis)*/
0x31,
0x09, /*Usage(Wheel)*/
0x38,
/* 40 */
0x15, /*Logical Minimum(-127)*/
0x81,
0x25, /*Logical Maximum(127)*/
0x7F,
0x75, /*Report Size(8)*/
0x08,
0x95, /*Report Count(3)*/
0x03,
/* 48 */
0x81, /*Input(Variable, Relative)*/
0x06,
0xC0, /*End Collection*/
0x09,
0x3c,
0x05,
0xff,
0x09,
/* 56 */
0x01,
0x15,
0x00,
0x25,
0x01,
0x75,
0x01,
0x95,
/* 64 */
0x02,
0xb1,
0x22,
0x75,
0x06,
0x95,
0x01,
0xb1,
/* 72 */
0x01,
0xc0
}
; /* Joystick_ReportDescriptor */
//字符串描述符
/* USB String Descriptors (optional) */
const u8 Joystick_StringLangID[JOYSTICK_SIZ_STRING_LANGID] =
{
JOYSTICK_SIZ_STRING_LANGID,
USB_STRING_DESCRIPTOR_TYPE,
0x09,
0x04
}
; /* LangID = 0x0409: U.S. English */
最后还有几个字符描述符，这里就不copy了。
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