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espressif,esp32-pcnt

Vendor: Espressif Systems

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.
The ESP32S2's PCNT module has 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

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.

Child node properties

Name

Type

Details

reg

int

The PCNT unit index.
The ESP32 has 8 PCNT units. ESP32S2 has 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