...
Listing - Mouse Report Descriptor Example presents an example of table declaration defining a Report descriptor corresponding to a mouse. The example matches the mouse report descriptor viewed by the host HID parser in Figure - Report Descriptor Content from a Host HID Parser View. The mouse report represents an Input report. Refer to the Report section for more details about the Report descriptor format. The items inside a collection are intentionally indented for code clarity.
| Anchor | ||||
|---|---|---|---|---|
|
| Code Block | ||||
|---|---|---|---|---|
| ||||
static CPU_INT08U App_USBD_HID_ReportDesc[] = { (1) (2)
USBD_HID_GLOBAL_USAGE_PAGE + 1, USBD_HID_USAGE_PAGE_GENERIC_DESKTOP_CONTROLS,
USBD_HID_LOCAL_USAGE + 1, USBD_HID_CA_MOUSE, (3)
USBD_HID_MAIN_COLLECTION + 1, USBD_HID_COLLECTION_APPLICATION, (4)
USBD_HID_LOCAL_USAGE + 1, USBD_HID_CP_POINTER, (5)
USBD_HID_MAIN_COLLECTION + 1, USBD_HID_COLLECTION_PHYSICAL, (6)
USBD_HID_GLOBAL_USAGE_PAGE + 1, USBD_HID_USAGE_PAGE_BUTTON, (7)
USBD_HID_LOCAL_USAGE_MIN + 1, 0x01,
USBD_HID_LOCAL_USAGE_MAX + 1, 0x03,
USBD_HID_GLOBAL_LOG_MIN + 1, 0x00,
USBD_HID_GLOBAL_LOG_MAX + 1, 0x01,
USBD_HID_GLOBAL_REPORT_COUNT + 1, 0x03,
USBD_HID_GLOBAL_REPORT_SIZE + 1, 0x01,
USBD_HID_MAIN_INPUT + 1, USBD_HID_MAIN_DATA |
USBD_HID_MAIN_VARIABLE |
USBD_HID_MAIN_ABSOLUTE,
USBD_HID_GLOBAL_REPORT_COUNT + 1, 0x01, (8)
USBD_HID_GLOBAL_REPORT_SIZE + 1, 0x0D,
USBD_HID_MAIN_INPUT + 1, USBD_HID_MAIN_CONSTANT,
(9)
USBD_HID_GLOBAL_USAGE_PAGE + 1, USBD_HID_USAGE_PAGE_GENERIC_DESKTOP_CONTROLS,
USBD_HID_LOCAL_USAGE + 1, USBD_HID_DV_X,
USBD_HID_LOCAL_USAGE + 1, USBD_HID_DV_Y,
USBD_HID_GLOBAL_LOG_MIN + 1, 0x81,
USBD_HID_GLOBAL_LOG_MAX + 1, 0x7F,
USBD_HID_GLOBAL_REPORT_SIZE + 1, 0x08,
USBD_HID_GLOBAL_REPORT_COUNT + 1, 0x02,
USBD_HID_MAIN_INPUT + 1, USBD_HID_MAIN_DATA |
USBD_HID_MAIN_VARIABLE |
USBD_HID_MAIN_RELATIVE,
USBD_HID_MAIN_ENDCOLLECTION, (10)
USBD_HID_MAIN_ENDCOLLECTION (11)
}; |
...
| Panel |
|---|
(1) The table representing a mouse Report descriptor is initialized in such way that each line corresponds to a short item. The latter is formed from a 1-byte prefix and a 1-byte data. Refer to “Device Class Definition for Human Interface Devices (HID) Version 1.11”, sections 5.3 and 6.2.2.2 for more details about short items format. This table content corresponds to the mouse Report descriptor content viewed by a host HID parser in Figure - Report Descriptor Content from a Host HID Parser View. (2) The Generic Desktop Usage Page is used. (3) Within the Generic Desktop Usage Page, the usage tag suggests that the group of controls is for controlling a mouse. A mouse collection typically consists of two axes (X and Y) and one, two, or three buttons. (4) The mouse collection is started. (5) Within the mouse collection, a usage tag suggests more specifically that the mouse controls belong to the pointer collection. A pointer collection is a collection of axes that generates a value to direct, indicate, or point user intentions to an application. (6) The pointer collection is started. (7) The Buttons Usage Page defines an Input item composed of three 1-bit fields. Each 1-bit field represents the mouse’s button 1, 2 and 3 respectively and can return a value of 0 or 1. (8) The Input Item for the Buttons Usage Page is padded with 13 other bits. (9) Another Generic Desktop Usage Page is indicated for describing the mouse position with the axes X and Y. The Input item is composed of two 8-bit fields whose value can be between -127 and 127. (10) The pointer collection is closed. (11) The mouse collection is closed. |
...
Synchronous communication means that the transfer is blocking. Upon function call, the applications blocks until the transfer completion with or without an error. A timeout can be specified to avoid waiting forever.
presents Listing - Synchronous Bulk Read and Write Example presents a read and write example to receive data from the host using the interrupt OUT endpoint and to send data to the host using the interrupt IN endpoint.
...
Asynchronous communication means that the transfer is non-blocking. Upon function call, the application passes the transfer information to the device stack and does not block. Other application processing can be done while the transfer is in progress over the USB bus. Once the transfer is completed, a callback is called by the device stack to inform the application about the transfer completion.
Listing - Asynchronous Bulk Read and Write Example shows an example of an asynchronous read and write.
...