Pigpiox

Pigpiox is a wrapper around pigpiod for the Raspberry Pi. For all of pigpio's features, check out its documentation.

Requirements

To use Pigpiox, pigpiod must be included in your firmware. Currently, this is included by default on nerves_system_rpi0, but not on other Pi systems.

If you'd like to use Pigpiox on one of those systems, customize the nerves system you're interested in, and add BR2_PACKAGE_PIGPIO=y to its nerves_defconfig.

Installation

In your firmware's mix.exs, add pigpiox to your deps for your system target:

def deps(target) do
  [ system(target),
    {:pigpiox, "~> 0.1"}
  ]

Usage

Adding pigpiox as a dependency to your system will automatically launch the pigpio daemon and open a socket to communicate with it. To interact with pigpiod, Pigpiox provides various modules exposing different areas of functionality.

All documentation available on hexdocs.

GPIO

Basic functionality

The Pigpiox.GPIO provides basic GPIO functionality. Here's an example of reading and writing a GPIO:

gpio = 17

Pigpiox.GPIO.set_mode(gpio, :input)
{:ok, level} = Pigpiox.GPIO.read(gpio)

Pigpiox.GPIO.set_mode(gpio, :output)
Pigpiox.GPIO.write(gpio, 1)

Watching a GPIO

When reading a GPIO, often it's useful to know immediately when its level changes, instead of having to constantly poll it. Here's an example:

{:ok, pid} = Pigpiox.GPIO.watch(gpio)

After setting up a watch on a GPIO pin, the calling process will receive messages of the format {:gpio_leveL_change, gpio, level} as its level change.

Waveforms

The Pigpiox.Waveform module provides functions that allow you to create and send waveforms on the Raspberry Pi. Here's an example of pulsing a GPIO on and off every 500ms:

pulses = [
  %Pigpiox.Waveform.Pulse{gpio_on: gpio, delay: 500000},
  %Pigpiox.Waveform.Pulse{gpio_off: gpio, delay: 500000}
]

Pigpiox.Waveform.add_generic(pulses)

{:ok, wave_id} = Pigpiox.Waveform.create()

Pigpiox.GPIO.set_mode(gpio, :output)

Pigpiox.Waveform.repeat(wave_id)

Clock

The Pigpiox.Clock module provides functions that allow you to set a clock on reserved pin.

Pigpiox.Clock.hardware_clk(gpio, 2_500_000)

Pulse-width modulation (PWM)

The Pigpiox.Pwm module provides functions that allow you to build and send waveforms with pigpiod. According to Raspberry Pi's GPIO usage documentation, here are the pins PWM is avaliable on:

• Software PWM: all pins
• Hardware PWM: GPIO12, GPIO13, GPIO18, GPIO19

Software PWM

Max value for level is 255. Here's an example of changing the brightness of an LED using software PWM.

gpio = 12
Pigpiox.Pwm.gpio_pwm(gpio, 255) # 100%
Pigpiox.Pwm.gpio_pwm(gpio, 127) # 50%
Pigpiox.Pwm.gpio_pwm(gpio, 25)  # 10%
Pigpiox.Pwm.gpio_pwm(gpio, 2)   # 1%

Hardware PWM

Max value for level is 1_000_000. Here's an example of changing the brightness of an LED using hardware PWM.

gpio = 12
frequency = 800
Pigpiox.Pwm.hardware_pwm(gpio, frequency, 1_000_000) # 100%
Pigpiox.Pwm.hardware_pwm(gpio, frequency, 500_000)   # 50%
Pigpiox.Pwm.hardware_pwm(gpio, frequency, 100_000)   # 10%
Pigpiox.Pwm.hardware_pwm(gpio, frequency, 10_000)    # 1%

Contributions

This library is still in a very early stage, and I'd appreciate any and all contributions. In particular, a short-term goal is getting feature parity with the python pigpiod client library.