dart_periphery

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pub package

Important hint

v0.9.x is an API change release, which fixes all the camel case warnings of the source code. When starting this project enums and variables from existing C und Java code were not converted to camel case.

e.g. GPIOdirection.GPIO_DIR_OUT changed to GPIOdirection.gpioDirOut

Introduction

dart_periphery is a Dart port of the native c-periphery library for Linux Peripheral I/O (GPIO, LED, PWM, SPI, I2C, MMIO and Serial peripheral I/O). This package is specially intended for SoCs like Raspberry Pi, NanoPi, Banana Pi et al.

What is c-periphery?

Abstract from the project web site:

c-periphery is a small C library for

  • GPIO,
  • LED,
  • PWM,
  • SPI,
  • I2C,
  • MMIO (Memory Mapped I/O)
  • Serial peripheral I/O

interface access in userspace Linux. c-periphery simplifies and consolidates the native Linux APIs to these interfaces. c-periphery is useful in embedded Linux environments (including Raspberry Pi, BeagleBone, etc. platforms) for interfacing with external peripherals. c-periphery is re-entrant, has no dependencies outside the standard C library and Linux, compiles into a static library for easy integration with other projects, and is MIT licensed

dart_periphery binds the c-periphery library with the help of the dart:ffi mechanism. Nevertheless, dart_periphery tries to be close as possible to the original library. See following documentation. Thanks to Vanya Sergeev for his great job!

Why c-periphery?

The number of GPIO libraries/interfaces is becoming increasingly smaller.

dart_periphery - all interfaces are ported:

Examples

GPIO

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import 'package:dart_periphery/dart_periphery.dart';
import 'dart:io';

void main() {
  var config = GPIOconfig();
  config.direction = GPIOdirection.gpioDirOut;
  print('Native c-periphery Version :  ${getCperipheryVersion()}');
  print('GPIO test');
  var gpio = GPIO(18, GPIOdirection.gpioDirOut);
  var gpio2 = GPIO(16, GPIOdirection.gpioDirOut;
  var gpio3 = GPIO.advanced(5, config);

  print('GPIO info: ' + gpio.getGPIOinfo());

  print('GPIO native file handle: ${gpio.getGPIOfd()}');
  print('GPIO chip name: ${gpio.getGPIOchipName()}');
  print('GPIO chip label: ${gpio.getGPIOchipLabel()}');
  print('GPIO chip name: ${gpio.getGPIOchipName()}');
  print('CPIO chip label: ${gpio.getGPIOchipLabel()}');

  for (var i = 0; i < 10; ++i) {
    gpio.write(true);
    gpio2.write(true);
    gpio3.write(true);
    sleep(Duration(milliseconds: 200));
    gpio.write(false);
    gpio2.write(false);
    gpio3.write(false);
    sleep(Duration(milliseconds: 200));
  }

  gpio.dispose();
  gpio2.dispose();
  gpio3.dispose();
}

I2C

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import 'package:dart_periphery/dart_periphery.dart';

/// https://wiki.seeedstudio.com/Grove-Barometer_Sensor-BME280/
/// Grove - Temp&Humi&Barometer Sensor (BME280) is a breakout board for Bosch BMP280 high-precision,
/// low-power combined humidity, pressure, and temperature sensor.
void main() {
  // Select the right I2C bus number /dev/i2c-?
  // 1 for Raspbery Pi, 0 for NanoPi (Armbian), 2 Banana Pi (Armbian)
  var i2c = I2C(1);
  try {
    print('I2C info:' + i2c.getI2Cinfo());
    var bme280 = BME280(i2c);
    var r = bme280.getValues();
    print('Temperature [°] ${r.temperature.toStringAsFixed(1)}');
    print('Humidity [%] ${r.humidity.toStringAsFixed(1)}');
    print('Pressure [hPa] ${r.pressure.toStringAsFixed(1)}');
  } finally {
    i2c.dispose();
  }
}


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import 'package:dart_periphery/dart_periphery.dart';

/// Grove - Temp&Humi Sensor(SHT31) is a highly reliable, accurate,
/// quick response and integrated temperature & humidity sensor.
void main() {
  // Select the right I2C bus number /dev/i2c-?
  // 1 for Raspbery Pi, 0 for NanoPi (Armbian), 2 Banana Pi (Armbian)
  var i2c = I2C(1);
  try {
    var sht31 = SHT31(i2c);
    print(sht31.getStatus());
    print('Serial number ${sht31.getSerialNumber()}');
    print('Sensor heater active: ${sht31.isHeaterOn()}');

    var r = sht31.getValues();
    print('SHT31 [t°] ${r.temperature.toStringAsFixed(2)}');
    print('SHT31 [%°] ${r.humidity.toStringAsFixed(2)}');
  } finally {
    i2c.dispose();
  }
}

SPI

import 'package:dart_periphery/dart_periphery.dart';

void main() {
  var spi = SPI(0, 0, SPImode.mode0, 1000000);
  try {
    print('SPI info:' + spi.getSPIinfo());
    var bme280 = BME280.spi(spi);
    var r = bme280.getValues();
    print('Temperature [°] ${r.temperature.toStringAsFixed(1)}');
    print('Humidity [%] ${r.humidity.toStringAsFixed(1)}');
    print('Pressure [hPa] ${r.pressure.toStringAsFixed(1)}');
  } finally {
    spi.dispose();
  }
}

Serial

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import 'package:dart_periphery/dart_periphery.dart';
import 'dart:io';

///
/// [COZIR CO2 Sensor](https://co2meters.com/Documentation/Manuals/Manual_GC_0024_0025_0026_Revised8.pdf)
///
void main() {
  print('Serial test - COZIR CO2 Sensor');
  var s = Serial('/dev/serial0', Baudrate.b9600);
  try {
    print('Serial interface info: ' + s.getSerialInfo());

    // Return firmware version and sensor serial number - two lines
    s.writeString('Y\r\n');
    var event = s.read(256, 1000);
    print(event.toString());

    // Request temperature, humidity and CO2 level.
    s.writeString('M 4164\r\n');
    // Select polling mode
    s.writeString('K 2\r\n');
    // print any response
    event = s.read(256, 1000);
    print('Response ${event.toString()}');
    sleep(Duration(seconds: 1));
    for (var i = 0; i < 5; ++i) {
      s.writeString('Q\r\n');
      event = s.read(256, 1000);
      print(event.toString());
      sleep(Duration(seconds: 5));
    }
  } finally {
    s.dispose();
  }
}

Led

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import 'package:dart_periphery/dart_periphery.dart';
import 'dart:io';

void main() {
  /// Nano Pi power led - see 'ls /sys/class/leds/'
  var led = Led('nanopi:red:pwr');
  try {
    print('Led handle: ${led.getLedInfo()}');
    print('Led name: ${led.getLedName()}');
    print('Led brightness: ${led.getBrightness()}');
    print('Led maximum brightness: ${led.getMaxBrightness()}');
    var inverse = !led.read();
    print('Original led status: ${(!inverse)}');
    print('Toggle led');
    led.write(inverse);
    sleep(Duration(seconds: 5));
    inverse = !inverse;
    print('Toggle led');
    led.write(inverse);
    sleep(Duration(seconds: 5));
    print('Toggle led');
    inverse = !inverse;
    led.write(inverse);
    sleep(Duration(seconds: 5));
    print('Toggle led');
    led.write(!inverse);
  } finally {
    led.dispose();
  }
}

PWM

Ensure that PWM is correct enabled. e.g. see the following documentation for the Raspberry Pi.

import 'package:dart_periphery/dart_periphery.dart';
import 'dart:io';

void main() {
  var pwm = PWM(0, 0);
  try {
    print(pwm.getPWMinfo());
    pwm.setPeriodNs(10000000);
    pwm.setDutyCycleNs(8000000);
    print(pwm.getPeriodNs());
    pwm.enable();
    print("Wait 20 seconds");
    sleep(Duration(seconds: 20));
    pwm.disable();
  } finally {
    pwm.dispose();
  }
}

MMIO

Memory Mapped I/O: Turns on a led at pin 18 on a Raspberry Pi using MMIO. This direct register access example is derived from elinux.org.

import 'package:dart_periphery/dart_periphery.dart';
import 'dart:io';

const int bcm2708PeriBase = 0x3F000000; // Raspberry Pi 3
const int gpioBase = bcm2708PeriBase + 0x200000;
const int blockSize = 4 * 1024;

class MemMappedGPIO {
  MMIO mmio;
  MemMappedGPIO(this.mmio);

  // #define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
  void setPinInput(final int pin) {
    var offset = (pin ~/ 10) * 4;
    var value = mmio[offset];
    value &= (~(7 << (((pin) % 10) * 3)));
    mmio[offset] = value;
  }

  // #define OUT_GPIO(g) *(gpio+((g)/10)) |=  (1<<(((g)%10)*3))
  void setPinOutput(final int pin) {
    setPinInput(pin);
    var offset = (pin ~/ 10) * 4;
    var value = mmio[offset];
    value |= (1 << (((pin) % 10) * 3));
    mmio[offset] = value;
  }

  // #define GPIO_SET *(gpio+7) - sets   bits which are 1 ignores bits which are 0
  void setPinHigh(int pin) {
    mmio[7 * 4] = 1 << pin;
  }

  // #define GPIO_CLR *(gpio+10) - clears bits which are 1 ignores bits which are 0
  void setPinLow(int pin) {
    mmio[10 * 4] = 1 << pin;
  }

  // #define GET_GPIO(g) (*(gpio+13)&(1<<g)) - 0 if LOW, (1<<g) if HIGH
  int getPin(int pin) {
    return mmio[13 * 4] & (1 << pin);
  }
}

void main() {
  // Needs root rights and the gpioBase must be correct!
  // var mmio = MMIO(gpioBase, blockSize);
  var mmio = MMIO.advanced(0, blockSize, '/dev/gpiomem');
  var gpio = MemMappedGPIO(mmio);
  try {
    print(mmio.getMMIOinfo());
    var pin = 18;
    print('Led (pin=18) on');
    gpio.setPinOutput(pin);
    gpio.setPinHigh(pin);
    sleep(Duration(seconds: 10));
    gpio.setPinLow(pin);
    print('Led (pin=18) off');
  } finally {
    mmio.dispose();
  }
}

Install Dart on Raspian and Armbian

1.) Go to the home directory

cd ~

2.) Download the last stable Dart SDK form archiv for your CPU architecture/OS.

ARMv7

wget https://storage.googleapis.com/dart-archive/channels/stable/release/2.16.2/sdk/dartsdk-linux-arm-release.zip
unzip dartsdk-linux-arm-release.zip

ARMv8

wget https://storage.googleapis.com/dart-archive/channels/stable/release/2.16.2/sdk/dartsdk-linux-arm64-release.zip
unzip dartsdk-linux-arm64-release.zip

x86

https://storage.googleapis.com/dart-archive/channels/stable/release/2.16.2/sdk/dartsdk-linux-ia32-release.zip
unzip dartsdk-linux-ia32-release.zip

x86_64

https://storage.googleapis.com/dart-archive/channels/stable/release/2.16.1/sdk/dartsdk-linux-x64-release.zip
unzip dartsdk-linux-x64-release.zip

3.) Unpack and install SDK

sudo mv dart-sdk /opt/
sudo chmod -R +rx /opt/dart-sdk

4.) Add the Dart SDK to the path

nano ~/.profile

following command

export PATH=$PATH:/opt/dart-sdk/bin

at the end of the file and call

source ~/.profile

to apply the changes.

Test the installion

pi@raspberrypi:~ $ dart --version
Dart SDK version: 2.16.1 (stable) (Tue Feb 8 12:02:33 2022 +0100) on "linux_arm64"

Native libraries

Currently dart_periphery ships with four prebuild native c-periphery libraries for

dart_periphery calls uname() function to detect the CPU architecture for loading the appropriate libray. This auto detection mechanism can fail. Internally the logic tries to match the uname -m value to predefined string values.

Following methods can be used to overwrite the auto loading of the prebuild library. But be aware, any of these methods to disable the auto detection must be called before any dart_periphery interface is used!

// enum CPU_ARCHITECTURE { X86, X86_64, ARM, ARM64 }
void setCPUarchitecture(CPU_ARCHITECTURE arch)

sets explicit the CPU architecture, which loads a library according following mapping

useSharedLibray();

If this method is called, dart_periphery loads the shared library. For this case c-periphery must be installed as a shared library. See for section Shared Library for details.

To load a custom library call

void setCustomLibrary(String absolutePath)

This method can also be helpful for a currently not supported platform.

For a dart native binary, which can be deployed

dart compile exe i2c_example.dart

call

// optional parameter enum CPU_ARCHITECTURE { X86, X86_64, ARM, ARM64 }
// to skip auto detection
void useLocalLibrary([CPU_ARCHITECTURE arch])

The appropriate library should be in same directory as the exe.

flutter-pi

dart_periphery works with flutter-pi, a light-weight Flutter Engine Embedder for Raspberry Pi. For flutter-pi the appropriate library must be copied inside the flutter asset directory.

The appropriate library is loaded by auto detection of the CPU architecture. If this way fails, the auto detection can be overruled by following two methods:

// enum CPU_ARCHITECTURE { X86, X86_64, ARM, ARM64 }
void setCPUarchitecture(CPU_ARCHITECTURE arch)
void setCustomLibrary(String absolutePath)

These methods must be called before any dart_periphery interface is used! See last section, native libraries for details.

For flutter-pi the method

List<String> getFlutterPiArgs();

returns the command line parameter list of the flutter-pi command. The last parameter contains the asset directory.

Tested SoC hardware

Supported devices (sensors, actuators, expansion hats and displays)

Next steps

Test matrix

Test suite

ArchitectureGPIOGPIOsysfsI2CSPISerialMMIO¹PWMLED
ARM ²
AARCH64 ³❌⁴
X86
X86_64

☐ missing test | ✅ test passed | ❌ test failed

¹ Delayed until FFI inline @Array() support in Dart Version >=2.13 is available

² Raspberry Pi 3 Model B

³ NanoPi Neo2 with a Allwinner H5, Quad-core 64-bit CPU

⁴ Fails for NanoPi, NanoPi Neo2 and Banana Pi on Armbian- same behavior like the original c-periphery test program. This is a point of deeper investigations

⁵ no X86/X86_64 SoC for testing available

Help wanted

  • Testing dart_periphery on different SoC platforms
  • Documentation review - I am not a native speaker.
  • Code review - this is my first public Dart project. I am a Java developer and probably I tend to solve problems rather in the Java than in the Dart way.

Libraries

dart_periphery