dts/bindings/input/gpio-qdec.yaml

# Copyright 2023 Google LLC
# SPDX-License-Identifier: Apache-2.0

description: |
  GPIO based QDEC input device

  Implement an input device generating relative axis event reports for a rotary
  encoder connected to two GPIOs. The driver is normally idling until it sees a
  transition on any of the encoder signal lines, then switches to polling mode
  and samples the two signal lines periodically to track the encoder position,
  and goes back to idling after the specified timeout.

  Example configuration:

  #include <zephyr/dt-bindings/input/input-event-codes.h>

  qdec {
          compatible = "gpio-qdec";
          gpios = <&gpio0 14 (GPIO_PULL_UP | GPIO_ACTIVE_HIGH)>,
                  <&gpio0 13 (GPIO_PULL_UP | GPIO_ACTIVE_HIGH)>;
          steps-per-period = <4>;
          zephyr,axis = <INPUT_REL_WHEEL>;
          sample-time-us = <2000>;
          idle-timeout-ms = <200>;
  };

compatible: "gpio-qdec"

include: base.yaml

properties:
  gpios:
    type: phandle-array
    required: true
    description: |
      GPIO for the A and B encoder signals.

  led-gpios:
    type: phandle-array
    description: |
      GPIOs for LED or other components needed for sensing the AB signals.

  led-pre-us:
    type: int
    description: |
      Time between enabling the led-gpios output pins and reading the encoder
      state on the input pins, meant to give the state detector (such a
      phototransistor) time to settle to right state. Required if led-gpios and
      idle-poll-time-us are specified, can be explicitly set to 0 for no delay.

  steps-per-period:
    type: int
    required: true
    description: |
      How many steps to count before reporting an input event.

  zephyr,axis:
    type: int
    required: true
    description: |
      The input code for the axis to report for the device, typically any of
      INPUT_REL_*.

  sample-time-us:
    type: int
    required: true
    description: |
      How often to sample the A and B signal lines when tracking the encoder
      movement.

  idle-poll-time-us:
    type: int
    description: |
      How often to sample the A and B signal while idling. If unset then the
      driver will use the GPIO interrupt to exit idle state, and any GPIO
      specified in led-gpios will be enabled all the time. If non zero, then
      the driver will poll every idle-poll-time-us microseconds while idle, and
      only activate led-gpios before sampling the encoder state.

  idle-timeout-ms:
    type: int
    required: true
    description: |
      Timeout for the last detected transition before stopping the sampling
      timer and going back to idle state.