Question

我正在使用BME280传感器跟踪Chris Pietschmann的Raspberry Pi气象站3.0教程：https://www.hackster.io/23021/weather-station-v-3-0-b8b8bc。

在MainPage中，他调用ReadTemperture（或传感器的任何其他寄存器）来写出返回的值。

我在Debug.Writeline（）中获取System.Threading.Tasks.Task`1 [System.Single]以获取所有值...温度，湿度，压力和海拔高度。

我在方法中添加了一条写字符，我得到了正确的值，所以我从传感器中读取...我只是无法将其返回主页并阅读它。

看起来我在异步方面遗漏了什么？

这是MainPage：

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using System.Threading.Tasks;
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;

// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409

namespace IoT_BME280_Temp
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        DispatcherTimer _timer;


        const float seaLevelPressure = 1026.00f;  //was 1022.00
        BME280Sensor _bme280 = new BME280Sensor();

        public MainPage()

        {
            this.InitializeComponent();
        }

        protected override async void OnNavigatedTo(NavigationEventArgs e)
        {
            base.OnNavigatedTo(e);


            await _bme280.Initialize();

            _timer = new DispatcherTimer();
            _timer.Interval = TimeSpan.FromSeconds(5);
            _timer.Tick += _timer_Tick;

            _timer.Start();

        }

        private void _timer_Tick(object sender, object e)
        {
            try
            {
                var temp     = _bme280.ReadTemperature();
                Debug.WriteLine("Temp: {0} deg C", temp);  // Results in: Temp: System.Threading.Tasks.Task`1[System.Single] deg C
                var humidity = _bme280.ReadHumidity();
                var pressure = _bme280.ReadPressure();
                var altitude = _bme280.ReadAltitude(seaLevelPressure);
            } 
        catch
            {
                Debug.WriteLine("Cannot read values from sensor...");
        }
        }
    }
}

这是来自BME280Sensor类的ReadTemprature（）：

public async Task<float> ReadTemperature()
    {
        //Make sure the I2C device is initialized
        if (!init) await Begin();

        //Read the MSB, LSB and bits 7:4 (XLSB) of the temperature from the BME280 registers
        byte tmsb = ReadByte((byte)eRegisters.BME280_REGISTER_TEMPDATA_MSB);
        byte tlsb = ReadByte((byte)eRegisters.BME280_REGISTER_TEMPDATA_LSB);
        byte txlsb = ReadByte((byte)eRegisters.BME280_REGISTER_TEMPDATA_XLSB); // bits 7:4

        //Combine the values into a 32-bit integer
        Int32 t = (tmsb << 12) + (tlsb << 4) + (txlsb >> 4);

        //Convert the raw value to the temperature in degC
        double temp = BME280_compensate_T_double(t);
        Debug.WriteLine("Temp: {0} deg C", temp);  //  This results in the correct temperature value...

        //Return the temperature as a float value
        return (float)temp;
    }

提前致谢！

Answer 1

你得到一个Task，因为当你同步调用它时，ReadTemperature会返回。要获取任务的结果而不是任务本身，您需要使用await调用方法，并将_timer_Tick更改为async：

private async void _timer_Tick(object sender, object e)
{
    try
    {
        var temp     = await _bme280.ReadTemperature();
        Debug.WriteLine("Temp: {0} deg C", temp);
        var humidity = _bme280.ReadHumidity();
        var pressure = _bme280.ReadPressure();
        var altitude = _bme280.ReadAltitude(seaLevelPressure);
    } 
    catch
    {
        Debug.WriteLine("Cannot read values from sensor...");
    }
}

Windows IoT核心读取值返回System.Threading.Tasks.Task`1 [System.Single]而不是float

1 个答案: