Specs

close(reference()) :: :ok

Release the resources associated with the GPIO.

This is optional. The garbage collector will free GPIO resources that aren't in use, but this will free them sooner.

Specs

info() :: map()

Return info about the low level GPIO interface

This may be helpful when debugging issues.

Specs

open(pin_number(), pin_direction(), [open_option()]) ::
  {:ok, reference()} | {:error, atom()}

Open a GPIO for use.

pin should be a valid GPIO pin number on the system and pin_direction should be :input or :output. If opening as an output, then be sure to set the :initial_value option if you need the set to be glitch free.

Options:

• :initial_value - Set to :not_set, 0 or 1 if this is an output. :not_set is the default.
• :pull_mode - Set to :not_set, :pullup, :pulldown, or :none for an input pin. :not_set is the default.

Specs

pin(reference()) :: pin_number()

Get the GPIO pin number

Specs

read(reference()) :: value()

Read the current value on a pin.

Specs

set_direction(reference(), pin_direction()) :: :ok | {:error, atom()}

Change the direction of the pin.

Specs

set_interrupts(reference(), trigger(), list()) :: :ok | {:error, atom()}

Enable or disable pin value change notifications. The notifications are sent based on the trigger parameter:

• :none - No notifications are sent
• :rising - Send a notification when the pin changes from 0 to 1
• :falling - Send a notification when the pin changes from 1 to 0
• :both - Send a notification on all changes

Available Options:

• suppress_glitches - It is possible that the pin transitions to a value and back by the time that Circuits GPIO gets to process it. This controls whether a notification is sent. Set this to false to receive notifications.
• receiver - Process which should receive the notifications. Defaults to the calling process (self())

Notifications look like:

{:circuits_gpio, pin_number, timestamp, value}

Where pin_number is the pin that changed values, timestamp is roughly when the transition occurred in nanoseconds since host system boot time, and value is the new value.

NOTE: You will need to store the Circuits.GPIO reference somewhere (like your GenServer's state) so that it doesn't get garbage collected. Event messages stop when it gets collected. If you only get one message and you are expecting more, this is likely the case.

Specs

set_pull_mode(reference(), pull_mode()) :: :ok | {:error, atom()}

Enable or disable internal pull-up or pull-down resistor to GPIO pin

Specs

write(reference(), value()) :: :ok

Set the value of a pin. The pin should be configured to an output for this to work.