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doc: drivers: gpio: detail scancodes from example

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Add more explanation and details on how to use
USB HID scancodes in gpio-emul-sdl implementation.

Signed-off-by: Eve Redero <eve.redero@gmail.com>
This commit is contained in:
Eve Redero 2024-03-05 16:19:44 +01:00 • committed by Fabio Baltieri
commit 959680166a
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9
dts/bindings/gpio/zephyr,gpio-emul-sdl.yaml
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@ -8,10 +8,19 @@ description: |
to be a child of a `zephyr,gpio-emul` compatible.
Add a list of scancodes for the desired keys to be mapped.
This driver uses USB HID scancodes, they are different from linux key codes,
and thus do not match Zephyr code values as described in input-event-codes.h.
Refer to https://www.usb.org/sites/default/files/documents/hut1_12v2.pdf
section Keyboard/Keypad (p53) for a list of scancode values.
The following example maps the first 3 numeric keys to GPIO pins:
- Scancode 30: "Keyboard 1 and !", mapped to gpio0 0
- Scancode 31: "Keyboard 2 and @", mapped to gpio0 1
- Scancode 32: "Keyboard 3 and \#", mapped to gpio0 2
The "typical position" column from HID table suggests to match them
with standard keycode values 2, 3 and 4, corresponding to
INPUT_KEY_1, INPUT_KEY_2 and INPUT_KEY_3 in input-event-codes.h.
/* gpio0 has to be a zephyr,gpio-emul device */
&gpio0 {