nodemcu-firmware/docs/modules/gpio.md

GPIO Module

Since	Origin / Contributor	Maintainer	Source
2016-11-26	Johny Mattsson	Johny Mattsson	gpio.c

This module provides access to the GPIO (General Purpose Input/Output) subsystem.

GPIO Overview

The ESP32 chip features 40 physical GPIO pads. Some GPIO pads cannot be used or do not have the corresponding pin on the chip package (refer to the ESP32 Datasheet).

• GPIO6-11 are usually used for SPI flash.
• GPIO20, GPIO24, and GPIO28-31 are not available as pins.
• GPIO34-39 can only be set as input mode and do not have software pullup or pulldown functions.

gpio.config()

Configure GPIO mode for one or more pins.

Syntax

gpio.config({
  gpio=x || {x, y, z},
  dir=gpio.IN || gpio.OUT || gpio.IN_OUT,
  opendrain= 0 || 1 -- only applicable to output modes
  pull= gpio.FLOATING || gpio.PULL_UP || gpio.PULL_DOWN || gpio.PULL_UP_DOWN
}, ...)

Parameters

List of configuration tables:

• gpio one or more (given as list) pins, see GPIO Overview
• dir direction, one of
  • gpio.IN
  • gpio.OUT
  • gpio.IN_OUT
• opendrain 1 enables opendrain mode, defaults to 0 if omitted
• pull enable pull-up and -down resistors, one of
  • gpio.FLOATING disables both pull-up and -down
  • gpio.PULL_UP enables pull-up and disables pull-down
  • gpio.PULL_DOWN enables pull-down and disables pull-up
  • gpio.PULL_UP_DOWN enables both pull-up and -down

Returns

nil

Example

gpio.config( { gpio={19,21}, dir=gpio.OUT }, { gpio=22, dir=gpio.IN, pull=gpio.PULL_UP })

gpio.read()

Read digital GPIO pin value.

Syntax

gpio.read(pin)

Parameters

pin pin to read, see GPIO Overview

Returns

0 = low, 1 = high

gpio.set_drive()

Set the drive strength of a given GPIO pin. The higher the drive strength, the more current can be sourced/sunk from the pin. The exact maximum depends on the power domain of the pin and how much current other pins in that domain are consuming.

Syntax

gpio.set_drive(pin, strength)

Parameters

• pin, a valid GPIO pin number.
• strength the drive strength to set, one of
  • gpio.DRIVE_0 weakest drive strength
  • gpio.DRIVE_1 stronger drive strength
  • gpio.DRIVE_2 default drive strength
  • gpio.DRIVE_DEFAULT default drive strength (same as DRIVE_2)
  • gpio.DRIVE_3 maximum drive strength

Returns

nil

Example

gpio.set_drive(4, gpio.DRIVE_3)

gpio.trig()

Establish or clear a callback function to run on interrupt for a GPIO.

Syntax

gpio.trig(pin [, type [, callback]])

Parameters

• pin, see GPIO Overview
• type trigger type, one of
  • gpio.INTR_DISABLE or nil to disable interrupts on this pin (in which case callback is ignored and should be nil or omitted)
  • gpio.INTR_UP for trigger on rising edge
  • gpio.INTR_DOWN for trigger on falling edge
  • gpio.INTR_UP_DOWN for trigger on both edges
  • gpio.INTR_LOW for trigger on low level
  • gpio.INTR_HIGH for trigger on high level
• callback optional function to be called when trigger fires. If nil or omitted (and type is not gpio.INTR_DISABLE) then any previously-set callback will continue to be used. Parameters are:
  • pin
  • level

Returns

nil

gpio.wakeup()

Configuring wake-from-sleep-on-GPIO-level.

Syntax

gpio.wakeup(pin, level)

Parameters

• pin, see GPIO Overview
• level wake-up level, one of
  • gpio.INTR_NONE to disable wake-up
  • gpio.INTR_LOW for wake-up on low level
  • gpio.INTR_HIGH for wake-up on high level

Returns

nil

gpio.write()

Set digital GPIO pin value.

Syntax

gpio.write(pin, level)

Parameters

• pin pin to write, see GPIO Overview
• level 1 or 0

Returns

nil