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espressif,esp32-pcnt

Description

Espressif's Pulse Counter Mode (PCNT) controller Node

The pulse counter module is designed to count the number of
rising and/or falling edges of an input signal.

The ESP32's PCNT module has 8 independent counting “units” numbered from 0 to 7.
ESP32S2 and ESP32S3 have 4 independent counting “units” numbered from 0 to 3.

Each pulse counter unit has a 16-bit signed counter register.

Each unit has two independent channel: ch0 and ch1 that can be configured
to either increment or decrement the counter.

Each channel has two inputs: a signal input that accepts signal edges
to be detected, as well as a control input that can be used to enable
or disable the signal input.

Each pulse counter unit also features a filter on each of the four inputs,
adding the option to ignore short glitches in the signals.

By combining the usage of both signal and control inputs, a PCNT unit can
act as a quadrature decoder.

Example: Use PCNT to read a rotary-enconder

The mapping between signal and control input and the pin is done through pinctrl:

  &pinctrl {
      pcnt_default: pcnt_default {
          group1 {
              pinmux = <PCNT0_CH0SIG_GPIO14>,
                      <PCNT0_CH0CTRL_GPIO15>;
              bias-pull-up;
          };
      };
  };

Note: Check espressif,esp32-pinctrl.yaml for complete documentation regarding pinctrl.

Use the PCNT node to configure the module:

  &pcnt {
    pinctrl-0 = <&pcnt_default>;
    pinctrl-names = "default";
    status = "okay";
    #address-cells = <1>;
    #size-cells = <0>;
    unit0@0 {
      reg = <0>;
      #address-cells = <1>;
      #size-cells = <0>;
      filter = <100>;
      channelA@0 {
          reg = <0>;
          sig-pos-mode = <2>;
          sig-neg-mode = <1>;
          ctrl-h-mode = <0>;
          ctrl-l-mode = <1>;
      };
    };
  };

Properties

Top level properties

These property descriptions apply to “espressif,esp32-pcnt” nodes themselves. This page also describes child node properties in the following sections.

Properties not inherited from the base binding file.

Name	Type	Details
`friendly-name`	`string`	Human readable string describing the sensor. It can be used to distinguish multiple instances of the same model (e.g., lid accelerometer vs. base accelerometer in a laptop) to a host operating system. This property is defined in the Generic Sensor Property Usages of the HID Usage Tables specification (https://usb.org/sites/default/files/hut1_3_0.pdf, section 22.5).
`pinctrl-0`	`phandles`	Pin configuration/s for the first state. Content is specific to the selected pin controller driver implementation.
`pinctrl-1`	`phandles`	Pin configuration/s for the second state. See pinctrl-0.
`pinctrl-2`	`phandles`	Pin configuration/s for the third state. See pinctrl-0.
`pinctrl-3`	`phandles`	Pin configuration/s for the fourth state. See pinctrl-0.
`pinctrl-4`	`phandles`	Pin configuration/s for the fifth state. See pinctrl-0.
`pinctrl-names`	`string-array`	Names for the provided states. The number of names needs to match the number of states.

Properties inherited from the base binding file, which defines common properties that may be set on many nodes. Not all of these may apply to the “espressif,esp32-pcnt” compatible.

Name	Type	Details
`wakeup-source`	`boolean`	Property to identify that a device can be used as wake up source. When this property is provided a specific flag is set into the device that tells the system that the device is capable of wake up the system. Wake up capable devices are disabled (interruptions will not wake up the system) by default but they can be enabled at runtime if necessary.
`power-domain`	`phandle`	Power domain the device belongs to. The device will be notified when the power domain it belongs to is either suspended or resumed.
`zephyr,pm-device-runtime-auto`	`boolean`	Automatically configure the device for runtime power management after the init function runs.
`zephyr,disabling-power-states`	`phandles`	List of power states that will disable this device power.
`status`	`string`	indicates the operational status of a device Legal values: `'ok'`, `'okay'`, `'disabled'`, `'reserved'`, `'fail'`, `'fail-sss'` See Important properties for more information.
`compatible`	`string-array`	compatible strings This property is required. See Important properties for more information.
`reg`	`array`	register space See Important properties for more information.
`reg-names`	`string-array`	name of each register space
`interrupts`	`array`	interrupts for device See Important properties for more information.
`interrupts-extended`	`compound`	extended interrupt specifier for device
`interrupt-names`	`string-array`	name of each interrupt
`interrupt-parent`	`phandle`	phandle to interrupt controller node
`label`	`string`	Human readable string describing the device (used as device_get_binding() argument) See Important properties for more information. This property is deprecated.
`clocks`	`phandle-array`	Clock gate information
`clock-names`	`string-array`	name of each clock
`#address-cells`	`int`	number of address cells in reg property
`#size-cells`	`int`	number of size cells in reg property
`dmas`	`phandle-array`	DMA channels specifiers
`dma-names`	`string-array`	Provided names of DMA channel specifiers
`io-channels`	`phandle-array`	IO channels specifiers
`io-channel-names`	`string-array`	Provided names of IO channel specifiers
`mboxes`	`phandle-array`	mailbox / IPM channels specifiers
`mbox-names`	`string-array`	Provided names of mailbox / IPM channel specifiers
`zephyr,deferred-init`	`boolean`	Do not initialize device automatically on boot. Device should be manually initialized using device_init().

Child node properties

Name

Type

Details

reg

int

The PCNT unit index.
The ESP32 has 8 PCNT units. ESP32S2/S3 have 4 PCNT units.

This property is required.

Legal values: 0, 1, 2, 3, 4, 5, 6, 7

See Important properties for more information.

filter

int

Pulse length (ns) to be ignored

Grandchild node properties

Name	Type	Details
`reg`	`int`	The PCNT channel index. This property is required. Legal values: `0`, `1` See Important properties for more information.
`sig-pos-mode`	`int`	Define what to do on the positive edge of pulse input. 0 (Default) - Inhibit counter (counter value will not change in this condition). 1 - Increase counter value. 2 - Decrease counter value. Legal values: `0`, `1`, `2`
`sig-neg-mode`	`int`	Define what to do on the negative edge of pulse input. 0 (Default) - Inhibit counter (counter value will not change in this condition). 1 - Increase counter value. 2 - Decrease counter value. Legal values: `0`, `1`, `2`
`ctrl-h-mode`	`int`	Define what to do when the control input is high. 0 (Default) - Don't change counter mode. 1 - Invert counter mode(increase -> decrease, decrease -> increase). 2 - Control mode: Inhibit counter (counter value will not change in this condition). Legal values: `0`, `1`, `2`
`ctrl-l-mode`	`int`	Define what to do when the control input is low. 0 (Default) - Don't change counter mode. 1 - Invert counter mode(increase -> decrease, decrease -> increase). 2 - Control mode: Inhibit counter (counter value will not change in this condition). Legal values: `0`, `1`, `2`