gpio-qdec

Vendor: Generic or vendor-independent

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>;
};

Properties

Properties not inherited from the base binding file.

Name

Type

Details

gpios

phandle-array

 
GPIO for the A and B encoder signals.

This property is required.

led-gpios

phandle-array

 
GPIOs for LED or other components needed for sensing the AB signals.

led-pre-us

int

 
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

int

 
How many steps to count before reporting an input event.

This property is required.

zephyr,axis

int

 
The input code for the axis to report for the device, typically any of
INPUT_REL_*.

This property is required.

sample-time-us

int

 
How often to sample the A and B signal lines when tracking the encoder
movement.

This property is required.

idle-poll-time-us

int

 
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

int

 
Timeout for the last detected transition before stopping the sampling
timer and going back to idle state.

This property is required.