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GPIOCTL(8) System Manager's Manual GPIOCTL(8)

gpioctlcontrol GPIO devices

gpioctl [-q] device pin [0 | 1 | 2 | on | off | toggle]

gpioctl [-q] device pin set [flags] [name]

gpioctl [-q] device pin unset

gpioctl [-q] device attach device offset mask [flag]

gpioctl [-q] device detach device

The gpioctl program allows manipulation of GPIO (General Purpose Input/Output) device pins. Such devices can be either part of the chipset or embedded CPU, or a separate chip. The usual way of using GPIO is to connect some simple devices such as LEDs and 1-wire thermal sensors to its pins.

Each GPIO device has an associated device file in the /dev directory. device can be specified with or without the /dev prefix. For example, /dev/gpio0 or gpio0.

GPIO pins can be either “read” or “written” with the values of logical 0 or 1. If only a pin number is specified on the command line, the pin state will be read from the GPIO controller and displayed. To write to a pin, a value must be specified after the pin number. Values can be either 0 or 1. A value of 2 has a special meaning: it “toggles” the pin, i.e. changes its state to the opposite. Instead of the numerical values, the word on, off, or toggle can be used.

Only pins that have been configured at securelevel 0, typically during system startup, are accessible once the securelevel has been raised. Pins can be given symbolic names for easier use. Besides using individual pins, device drivers that use GPIO pins can be attached to a gpio(4) device using the gpioctl command.

The following configuration flags are supported by the GPIO framework. Note that not all the flags can be supported by the particular GPIO controller.

input direction
output direction
open-drain output
push-pull output
tri-state (output disabled)
internal pull-up enabled
internal pull-down enabled
invert input
invert output

When attaching an I2C device, if the flag argument is set to 0x01, the order of the SDA and SCL signals is reversed (see gpioiic(4)).

When executed with only the gpio(4) device name as argument, gpioctl reads information about the GPIO device and displays it. At securelevel 0 the number of physically available pins is displayed, at higher securelevels the number of configured (set) pins is displayed.

The options are as follows:

Operate quietly i.e. nothing is printed to stdout.

GPIO device unit u file.

Configure pin 20 to have push-pull output:

# gpioctl gpio0 20 set out pp

Write logical 1 to pin 20:

# gpioctl gpio0 20 1

Attach a onewire(4) bus on a gpioow(4) device on pin 4:

# gpioctl gpio0 attach gpioow 4 0x01

Detach the gpioow0 device:

# gpioctl gpio0 detach gpioow0

Configure pin 5 as output and name it error_led:

# gpioctl gpio0 5 set out error_led

Toggle the error_led:

# gpioctl gpio0 error_led 2


The gpioctl command first appeared in OpenBSD 3.6.

The gpioctl program was written by Alexander Yurchenko ⟨⟩. Device attachment was added by
Marc Balmer ⟨⟩.

October 4, 2011 OpenBSD-5.1