UM0290 datasheet(25/76 Pages) STMICROELECTRONICS

25 / 76 page

UM0290

Custom HID

25/76

Each Report descriptor is related to a specific component in the evaluation board (LEDs,

push button or ADC). The following section described the functionality of these reports.

3.3

Custom HID implementation

3.3.1

LEDs control

The STR7xx/91x evaluation boards have four LEDs. In the Custom HID demo each LED

correspond to a specific report (report 1 to 4) and the LEDs states (ON/OFF) are set by the

PC applet.

When the device receive data on the endpoint 1 OUT the function “EP1_OUT_Callback()” is

called to dispatch the received state to the correspondent LED according to the report

number. The received data has the following format:

Figure 4.

Data OUT format

Report Num: report number from 1 to 4.

LED State: 0 -> LED OFF

1 -> LED ON

3.3.2

Push button states report

The state of the Key push button is reported to the PC host using the endpoint 1 IN.

The Key button corresponds to the report 5. When this button is pressed the device sends to

the host the related report number and the button state using the following format:

Figure 5.

Data IN Format

Report Num: report number (5).

Button State: 1 -> button pressed.

3.3.3

ADC converted data transfer

This part of the demo consists of the transfer to the PC host the result of the converted

voltage connected to the potentiometer of the evaluation board. The ADC is configured in

continuous mode to a RAM variable (ADC_ConvertedValueX). After each conversion we

test the converted value with an old one (ADC_ConvertedValueX_1) and if we find a

difference between the two values (potentiometer value changed by a user) the new value is

sent to the PC using the endpoint 1 IN.

Note:

The data format is the same as the push buttons, but the report number (7) is followed by

UM0290 Datasheet(PDF) 25 Page - STMicroelectronics