rpi_gpio.dart

rpi_gpio is a Dart package for accessing the Raspberry Pi GPIO pins.

Overview

• The Gpio library provides the API for accessing the various General Purpose I/O pins on the Raspberry Pi.

• RpiGpio provides the implementation for the Gpio API derived from the WiringPi library.

Setup

Installing libgpiod (should already be installed)

RpiGpio accesses the GPIO pins using the native libgpiod.so.2 library. If you are running the latest Raspberry Pi OS (formerly Raspbian), then this library should already be installed by default on your Raspberry Pi. If you are unsure, see #2 below in the troubleshooting section. If it is not already installed, open a terminal and run

sudo apt update
sudo apt install libgpiod2

Example

The example launches the example app to demonstrate:

• Blinking an LED along with software based PWM on a second LED.

• Responding to a button press by turning on an LED.

The example is structured such that the example test can inject a mock gpio to facilitate testing and allow test execution on platforms other than the Raspberry Pi.

Testing

Latest Raspberry Pi OS (2024-05-29)

Raspberry Pi Hardware	Dart version
Pi 5 Model B Rev 1.0	3.3.4 (stable) (Tue Apr 16 19:56:12 2024 +0000) on "linux_arm64"
Pi 3 Model B Rev 1.2	3.3.4 (stable) (Tue Apr 16 19:56:12 2024 +0000) on "linux_arm64"
Pi 2 Model B Rev 1.1	3.3.4 - 32 bit

Troubleshooting

1. Run test/src/native/show_hardware_and_os.dart and record the output

2. Run test/src/native/show_lib_version.dart to see if the libgpiod.so.2 library can be located

3. If running test/src/native/blink_led.dart crashes then there may be a 32 bit / 64 bit mismatch. Check that the board, the OS, and the Dart SDK are all either 32 bit or 64 bit.

4. If running test/src/native/blink_led.dart doesn't crash, but doesn't blink the LED (where the LED and resistor are connected in series to GPIO 17 (pin 11) and ground) then

sudo apt-get install libgpiod-dev
gpioinfo

and and check to see that the gpiochip# listing all of the GPIO# (for example "gpiochip4" below)

$ gpioinfo
gpiochip0 - 32 lines:
  ...
gpiochip4 - 54 lines:
	line   0:     "ID_SDA"       unused   input  active-high
	line   1:     "ID_SCL"       unused   input  active-high
	line   2:      "GPIO2"       unused   input  active-high
	line   3:      "GPIO3"       unused   input  active-high
	line   4:      "GPIO4"       unused   input  active-high
  ...

matches the Gpio Chip information in #1 above. (for example "gpiochip4" below)

$ dart test/src/native/show_hardware_and_os.dart
CPU          : aarch64
  ...
Is Rpi 5     : true
Gpio Chip    : gpiochip4