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raspberrypi,pico-pinctrl

Vendor: Raspberry Pi Foundation

Description

The RPi Pico pin controller is a node responsible for controlling
pin function selection and pin properties, such as routing a UART0 Rx
to pin 1 and enabling the pullup resistor on that pin.

The node has the 'pinctrl' node label set in your SoC's devicetree,
so you can modify it like this:

  &pinctrl {
          /* your modifications go here */
  };

All device pin configurations should be placed in child nodes of the
'pinctrl' node, as shown in this example:

  /* You can put this in places like a board-pinctrl.dtsi file in
   * your board directory, or a devicetree overlay in your application.
   */

  /* include pre-defined combinations for the SoC variant used by the board */
  #include <dt-bindings/pinctrl/rpi-pico-rp2040-pinctrl.h>

  &pinctrl {
    /* configuration for the usart0 "default" state */
    uart0_default: uart0_default {
      /* group 1 */
      group1 {
        /* configure P0 as UART0 TX */
        pinmux = <UART0_TX_P0>;
      };
      /* group 2 */
      group2 {
        /* configure P1 as UART0 RX */
        pinmux = <UART0_RX_P1>;
        /* enable input on pin 1 */
        input-enable;
      };
    };
  };

The 'uart0_default' child node encodes the pin configurations for a
particular state of a device; in this case, the default (that is, active)
state.

As shown, pin configurations are organized in groups within each child node.
Each group can specify a list of pin function selections in the 'pinmux'
property.

A group can also specify shared pin properties common to all the specified
pins, such as the 'input-enable' property in group 2. Here is a list of
supported standard pin properties:

- bias-disable: Disable pull-up/down (default, not required).
- bias-pull-up: Enable pull-up resistor.
- bias-pull-down: Enable pull-down resistor.
- input-enable: Enable input from the pin.
- input-schmitt-enable: Enable input hysteresys.
- drive-strength: Set the drive strength of the pin, in milliamps. Possible
  values are: 2, 4, 8, 12 (default: 4mA)
- slew-rate: If set to 0, slew rate is set to slow. If set to 1, it is set
  to fast.

To link pin configurations with a device, use a pinctrl-N property for some
number N, like this example you could place in your board's DTS file:

   #include "board-pinctrl.dtsi"

   &uart0 {
         pinctrl-0 = <&uart0_default>;
         pinctrl-1 = <&uart0_sleep>;
         pinctrl-names = "default", "sleep";
   };

Properties

Top level properties

These property descriptions apply to “raspberrypi,pico-pinctrl” nodes themselves. This page also describes child node properties in the following sections.

Properties not inherited from the base binding file.

(None)

Grandchild node properties

Name

Type

Details

pinmux

array

An array of pins sharing the same group properties. Each
element of the array is an integer constructed from the
pin number and the alternative function of the pin.

This property is required.

drive-strength

int

The drive strength of a pin, in mA. The default value is 4mA, as this
is the power on reset value.

Default value: 4

Legal values: 2, 4, 8, 12

slew-rate

int

The slew rate of a pin. 0 corresponds to slow, and 1 corresponds to fast.
The default value is 0 (slow), as this is the power on reset value.

Legal values: 0, 1

bias-disable

boolean

disable any pin bias

bias-pull-up

boolean

enable pull-up resistor

bias-pull-down

boolean

enable pull-down resistor

input-enable

boolean

enable input on pin (no effect on output, such as enabling an input
buffer)

input-schmitt-enable

boolean

enable schmitt-trigger mode