1# Copyright 2023 Google LLC
2# SPDX-License-Identifier: Apache-2.0
3
4description: |
5  GPIO based QDEC input device
6
7  Implement an input device generating relative axis event reports for a rotary
8  encoder connected to two GPIOs. The driver is normally idling until it sees a
9  transition on any of the encoder signal lines, then switches to polling mode
10  and samples the two signal lines periodically to track the encoder position,
11  and goes back to idling after the specified timeout.
12
13  Example configuration:
14
15  #include <zephyr/dt-bindings/input/input-event-codes.h>
16
17  qdec {
18          compatible = "gpio-qdec";
19          gpios = <&gpio0 14 (GPIO_PULL_UP | GPIO_ACTIVE_HIGH)>,
20                  <&gpio0 13 (GPIO_PULL_UP | GPIO_ACTIVE_HIGH)>;
21          steps-per-period = <4>;
22          zephyr,axis = <INPUT_REL_WHEEL>;
23          sample-time-us = <2000>;
24          idle-timeout-ms = <200>;
25  };
26
27compatible: "gpio-qdec"
28
29include: base.yaml
30
31properties:
32  gpios:
33    type: phandle-array
34    required: true
35    description: |
36      GPIO for the A and B encoder signals.
37
38  led-gpios:
39    type: phandle-array
40    description: |
41      GPIOs for LED or other components needed for sensing the AB signals.
42
43  led-pre-us:
44    type: int
45    description: |
46      Time between enabling the led-gpios output pins and reading the encoder
47      state on the input pins, meant to give the state detector (such a
48      phototransistor) time to settle to right state. Required if led-gpios and
49      idle-poll-time-us are specified, can be explicitly set to 0 for no delay.
50
51  steps-per-period:
52    type: int
53    required: true
54    description: |
55      How many steps to count before reporting an input event.
56
57  zephyr,axis:
58    type: int
59    required: true
60    description: |
61      The input code for the axis to report for the device, typically any of
62      INPUT_REL_*.
63
64  sample-time-us:
65    type: int
66    required: true
67    description: |
68      How often to sample the A and B signal lines when tracking the encoder
69      movement.
70
71  idle-poll-time-us:
72    type: int
73    description: |
74      How often to sample the A and B signal while idling. If unset then the
75      driver will use the GPIO interrupt to exit idle state, and any GPIO
76      specified in led-gpios will be enabled all the time. If non zero, then
77      the driver will poll every idle-poll-time-us microseconds while idle, and
78      only activate led-gpios before sampling the encoder state.
79
80  idle-timeout-ms:
81    type: int
82    required: true
83    description: |
84      Timeout for the last detected transition before stopping the sampling
85      timer and going back to idle state.
86