如何通过在UWP项目上使用I2C连接到Arduino的Raspberry Pi IoT打开和关闭LED？

Question

我有一个Arduino Uno和一个带有Windows IoT核心的Raspberry Pi 3。我曾尝试使用this method将一些信息传递给我的Arduino，就像告诉它启动一个引脚或获取并解析一个字符串一样。这种方法非常适合从Arduino获取信息（如传感器参数）。

我能够向Arduino发送一个字节并根据发送的字节在我的Arduino代码中进行操作（如获取数字2时的init引脚7）。但它只能工作一次。我必须重置Arduino以便它再次接受来自Raspberry Pi的字节（我可以打开一个从我的Raspberry Pi连接到Arduino但不能转向它的LED。反过来也是如此。

我的目标是在Raspberry Pi中创建一个用于控制事物的网站。但是开始我正在使用UWP。我正在尝试将数据从运行在Raspberry Pi 3上的IoT Core传递到Arduino Uno（不是相反），或者通过I2C连接管理和控制Arduino Uno引脚。

我的MainPage.xaml：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using Windows.Devices.I2c;
using System.Threading.Tasks;
// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409

namespace I2CComm {
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page {
        private I2cDevice arduio; // Used to Connect to Arduino
        private DispatcherTimer timer = new DispatcherTimer();
        public MainPage() {
            this.InitializeComponent();
            Initialiasecom();
        }
        public async void Initialiasecom() {
            var settings = new I2cConnectionSettings(0x40);
            // Slave Address of Arduino Uno
            settings.BusSpeed = I2cBusSpeed.FastMode;
            // this bus has 400Khz speed
            string aqs =  I2cDevice.GetDeviceSelector("I2C1");
            // This will return Advanced Query String which is used to select i2c device
            var dis = await Windows.Devices.Enumeration.DeviceInformation.FindAllAsync(aqs);
            arduio = await I2cDevice.FromIdAsync(dis[0].Id, settings);
            timer.Tick += Timer_Tick;
            // We will create an event handler
            timer.Interval = new TimeSpan(0,0,0,0,500);
            // Timer_Tick is executed every 500 milli second
            timer.Start();
        }

        private async void Timer_Tick(object sender, object e) {
            byte[] response = new byte[2];
            try {
                arduio.Read(response);
                // this function will read data from Arduino
            }
            catch (Exception p) {
                Windows.UI.Popups.MessageDialog msg = new Windows.UI.Popups.MessageDialog(p.Message);
                await msg.ShowAsync();
                // this will show error message(if any)
            }
        }

        private void TurnOn_Click(object sender, RoutedEventArgs e) {
            try {
                byte[] sendpos;
                sendpos = BitConverter.GetBytes(2);
                arduio.Write(sendpos);
            }
            catch (Exception p) {
                Windows.UI.Popups.MessageDialog msg = new Windows.UI.Popups.MessageDialog(p.Message);
            }
        }

        private void TurnOff_Click(object sender, RoutedEventArgs e) {
            try {
                byte[] sendpos;
                sendpos = BitConverter.GetBytes(1);
                arduio.Write(sendpos);
            }
            catch (Exception p) {
                Windows.UI.Popups.MessageDialog msg = new Windows.UI.Popups.MessageDialog(p.Message);
            }
        }
    }
}

我的Arduino代码是：

#include <Wire.h>
// Library that contains functions to have I2C Communication
#define SLAVE_ADDRESS 0x40
// Define the I2C address to Communicate to Uno

byte response[2]; // this data is sent to PI
volatile short LDR_value; // Global Declaration
const int LDR_pin=A0; //pin to which LDR is connected A0 is analog A0 pin
const int ledPin = 7;

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
  Wire.begin(SLAVE_ADDRESS);
  // this will begin I2C Connection with 0x40 address
  Wire.onRequest(sendData);
  // sendData is a function called when Pi requests data
  Wire.onReceive(I2CReceived);
  pinMode(LDR_pin,INPUT);
  digitalWrite(ledPin, HIGH);
}

void loop() {
  delay(500);
}

void I2CReceived(int NumberOfBytes) {
  /* WinIoT have sent data byte; read it */
  byte ReceivedData = Wire.read();
  Serial.println(ReceivedData);
  if (ReceivedData == 2) {
    digitalWrite(ledPin, HIGH);
    return;
  } else if (ReceivedData == 1) {
    digitalWrite(ledPin, LOW);
    return;
  }
}

void sendData() {
  LDR_value=analogRead(LDR_pin);
  // Arduino returns 10-bit data but we need to convert it to 8 bits
  LDR_value=map(LDR_value,0,1023,0,255);
  response[0]=(byte)LDR_value;
  Wire.write(response,2); // return data to PI
}

Answer 1

Raspberry Pi发送4个字节（2是Int）而不是1个字节。您需要接收Arduino中的所有字节。你可以这样做：

void I2CReceived(int NumberOfBytes) {
  /* WinIoT have sent data byte; read it */
  byte ReceivedData = Wire.read();
  Serial.println(ReceivedData);

  while (0 < Wire.available()) {
    byte UselessData = Wire.read();
    Serial.println(UselessData);
  }

  if (ReceivedData == 2) {
    digitalWrite(ledPin, HIGH);
    return;
  } else if (ReceivedData == 1) {
    digitalWrite(ledPin, LOW);
    return;
  }  
}