588 lines
24 KiB
C#
588 lines
24 KiB
C#
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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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using System;
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using System.Collections.Generic;
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using System.Device.I2c;
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using System.Linq;
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using NucuCar.Sensors.Environment.Bmxx80.CalibrationData;
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using NucuCar.Sensors.Environment.Bmxx80.FilteringMode;
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using NucuCar.Sensors.Environment.Bmxx80.PowerMode;
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using NucuCar.Sensors.Environment.Bmxx80.Register;
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using NucuCar.Sensors.Environment.Bmxx80.Units;
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namespace NucuCar.Sensors.Environment.Bmxx80
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{
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/// <summary>
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/// Represents a BME680 temperature, pressure, relative humidity and VOC gas sensor.
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/// </summary>
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public class Bme680 : Bmxx80Base
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{
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/// <summary>
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/// Default I2C bus address.
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/// </summary>
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public const byte DefaultI2cAddress = 0x76;
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/// <summary>
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/// Secondary I2C bus address.
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/// </summary>
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public const byte SecondaryI2cAddress = 0x77;
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/// <summary>
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/// The expected chip ID of the BME680.
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/// </summary>
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private const byte DeviceId = 0x61;
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/// <summary>
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/// Calibration data for the <see cref="Bme680"/>.
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/// </summary>
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private Bme680CalibrationData _bme680Calibration;
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/// <inheritdoc/>
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protected override int TempCalibrationFactor => 16;
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private readonly List<Bme680HeaterProfileConfig> _heaterConfigs = new List<Bme680HeaterProfileConfig>();
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private bool _gasConversionIsEnabled;
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private bool _heaterIsEnabled;
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private Bme680HeaterProfile _heaterProfile;
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private Bme680FilteringMode _filterMode;
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private Sampling _humiditySampling;
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private static readonly byte[] s_osToMeasCycles = { 0, 1, 2, 4, 8, 16 };
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private static readonly byte[] s_osToSwitchCount = { 0, 1, 1, 1, 1, 1 };
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private static readonly double[] s_k1Lookup = { 0.0, 0.0, 0.0, 0.0, 0.0, -1.0, 0.0, -0.8, 0.0, 0.0, -0.2, -0.5, 0.0, -1.0, 0.0, 0.0 };
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private static readonly double[] s_k2Lookup = { 0.0, 0.0, 0.0, 0.0, 0.1, 0.7, 0.0, -0.8, -0.1, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };
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/// <summary>
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/// Initialize a new instance of the <see cref="Bme680"/> class.
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/// </summary>
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/// <param name="i2cDevice">The <see cref="I2cDevice"/> to create with.</param>
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public Bme680(I2cDevice i2cDevice)
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: base(DeviceId, i2cDevice)
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{
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_communicationProtocol = CommunicationProtocol.I2c;
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}
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/// <summary>
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/// Gets or sets the humidity sampling.
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/// </summary>
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/// <exception cref="ArgumentOutOfRangeException">Thrown when the <see cref="Sampling"/> is set to an undefined mode.</exception>
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public Sampling HumiditySampling
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{
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get => _humiditySampling;
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set
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{
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if (!Enum.IsDefined(typeof(Sampling), value))
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{
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throw new ArgumentOutOfRangeException();
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}
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var status = Read8BitsFromRegister((byte)Bme680Register.CTRL_HUM);
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status = (byte)((status & (byte)~Bme680Mask.HUMIDITY_SAMPLING) | (byte)value);
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Span<byte> command = stackalloc[]
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{
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(byte)Bme680Register.CTRL_HUM, status
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};
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_i2cDevice.Write(command);
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_humiditySampling = value;
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}
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}
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/// <summary>
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/// Gets or sets the heater profile to be used for measurements.
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/// Current heater profile is only set if the chosen profile is configured.
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/// </summary>
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/// <exception cref="ArgumentOutOfRangeException">Thrown when the <see cref="Bme680HeaterProfile"/> is set to an undefined profile.</exception>
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public Bme680HeaterProfile HeaterProfile
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{
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get => _heaterProfile;
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set
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{
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if (_heaterConfigs.Exists(config => config.HeaterProfile == value))
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{
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if (!Enum.IsDefined(typeof(Bme680HeaterProfile), value))
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{
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throw new ArgumentOutOfRangeException();
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}
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var heaterProfile = Read8BitsFromRegister((byte)Bme680Register.CTRL_GAS_1);
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heaterProfile = (byte)((heaterProfile & (byte)~Bme680Mask.NB_CONV) | (byte)value);
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Span<byte> command = stackalloc[]
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{
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(byte)Bme680Register.CTRL_GAS_1, heaterProfile
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};
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_i2cDevice.Write(command);
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_heaterProfile = value;
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}
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}
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}
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/// <summary>
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/// Gets or sets the filtering mode to be used for measurements.
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/// </summary>
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/// <exception cref="ArgumentOutOfRangeException">Thrown when the <see cref="Bme680FilteringMode"/> is set to an undefined mode.</exception>
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public Bme680FilteringMode FilterMode
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{
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get => _filterMode;
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set
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{
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if (!Enum.IsDefined(typeof(Bme680FilteringMode), value))
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{
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throw new ArgumentOutOfRangeException();
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}
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var filter = Read8BitsFromRegister((byte)Bme680Register.CONFIG);
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filter = (byte)((filter & (byte)~Bme680Mask.FILTER_COEFFICIENT) | (byte)value << 2);
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Span<byte> command = stackalloc[]
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{
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(byte)Bme680Register.CONFIG, filter
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};
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_i2cDevice.Write(command);
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_filterMode = value;
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}
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}
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/// <summary>
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/// Gets or sets whether the heater is enabled.
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/// </summary>
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public bool HeaterIsEnabled
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{
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get => _heaterIsEnabled;
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set
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{
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var heaterStatus = Read8BitsFromRegister((byte)Bme680Register.CTRL_GAS_0);
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heaterStatus = (byte)((heaterStatus & (byte)~Bme680Mask.HEAT_OFF) | Convert.ToByte(!value) << 3);
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Span<byte> command = stackalloc[]
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{
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(byte)Bme680Register.CTRL_GAS_0, heaterStatus
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};
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_i2cDevice.Write(command);
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_heaterIsEnabled = value;
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}
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}
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/// <summary>
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/// Gets or sets whether gas conversions are enabled.
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/// </summary>
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public bool GasConversionIsEnabled
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{
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get => _gasConversionIsEnabled;
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set
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{
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var gasConversion = Read8BitsFromRegister((byte)Bme680Register.CTRL_GAS_1);
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gasConversion = (byte)((gasConversion & (byte)~Bme680Mask.RUN_GAS) | Convert.ToByte(value) << 4);
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Span<byte> command = stackalloc[]
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{
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(byte)Bme680Register.CTRL_GAS_1, gasConversion
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};
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_i2cDevice.Write(command);
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_gasConversionIsEnabled = value;
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}
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}
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/// <summary>
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/// Reads whether new data is available.
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/// </summary>
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public bool ReadNewDataIsAvailable()
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{
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var newData = Read8BitsFromRegister((byte)Bme680Register.STATUS);
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newData = (byte)(newData >> 7);
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return Convert.ToBoolean(newData);
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}
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/// <summary>
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/// Reads whether a gas measurement is in process.
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/// </summary>
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public bool ReadGasMeasurementInProcess()
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{
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var gasMeasInProcess = Read8BitsFromRegister((byte)Bme680Register.STATUS);
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gasMeasInProcess = (byte)((gasMeasInProcess & (byte)Bme680Mask.GAS_MEASURING) >> 6);
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return Convert.ToBoolean(gasMeasInProcess);
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}
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/// <summary>
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/// Reads whether a measurement of any kind is in process.
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/// </summary>
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public bool ReadMeasurementInProcess()
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{
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var measInProcess = Read8BitsFromRegister((byte)Bme680Register.STATUS);
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measInProcess = (byte)((measInProcess & (byte)Bme680Mask.MEASURING) >> 5);
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return Convert.ToBoolean(measInProcess);
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}
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/// <summary>
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/// Reads whether the target heater temperature is reached.
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/// </summary>
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public bool ReadHeaterIsStable()
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{
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var heaterStable = Read8BitsFromRegister((byte)Bme680Register.GAS_RANGE);
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heaterStable = (byte)((heaterStable & (byte)Bme680Mask.HEAT_STAB) >> 4);
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return Convert.ToBoolean(heaterStable);
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}
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/// <summary>
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/// Sets the power mode to the given mode
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/// </summary>
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/// <param name="powerMode">The <see cref="Bme680PowerMode"/> to set.</param>
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/// <exception cref="ArgumentOutOfRangeException">Thrown when the power mode does not match a defined mode in <see cref="Bme680PowerMode"/>.</exception>
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public void SetPowerMode(Bme680PowerMode powerMode)
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{
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if (!Enum.IsDefined(typeof(Bme680PowerMode), powerMode))
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{
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throw new ArgumentOutOfRangeException();
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}
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var status = Read8BitsFromRegister((byte)Bme680Register.CTRL_MEAS);
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status = (byte)((status & (byte)~Bme680Mask.PWR_MODE) | (byte)powerMode);
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Span<byte> command = stackalloc[]
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{
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(byte)Bme680Register.CTRL_MEAS, status
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};
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_i2cDevice.Write(command);
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}
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/// <summary>
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/// Configures a heater profile, making it ready for use.
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/// </summary>
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/// <param name="profile">The <see cref="Bme680HeaterProfile"/> to configure.</param>
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/// <param name="targetTemperature">The target temperature in °C. Ranging from 0-400.</param>
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/// <param name="duration">The duration in ms. Ranging from 0-4032.</param>
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/// <param name="ambientTemperature">The ambient temperature in °C.</param>
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/// <exception cref="ArgumentOutOfRangeException">Thrown when the heating profile does not match a defined profile in <see cref="Bme680HeaterProfile"/>.</exception>
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public void ConfigureHeatingProfile(Bme680HeaterProfile profile, ushort targetTemperature, ushort duration, double ambientTemperature)
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{
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if (!Enum.IsDefined(typeof(Bme680HeaterProfile), profile))
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{
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throw new ArgumentOutOfRangeException();
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}
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// read ambient temperature for resistance calculation
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var heaterResistance = CalculateHeaterResistance(targetTemperature, (short)ambientTemperature);
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var heaterDuration = CalculateHeaterDuration(duration);
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Span<byte> resistanceCommand = stackalloc[]
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{
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(byte)((byte)Bme680Register.RES_HEAT_0 + profile), heaterResistance
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};
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Span<byte> durationCommand = stackalloc[]
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{
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(byte)((byte)Bme680Register.GAS_WAIT_0 + profile), heaterDuration
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};
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_i2cDevice.Write(resistanceCommand);
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_i2cDevice.Write(durationCommand);
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// cache heater configuration
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if (_heaterConfigs.Exists(config => config.HeaterProfile == profile))
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{
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_heaterConfigs.Remove(_heaterConfigs.Single(config => config.HeaterProfile == profile));
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}
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_heaterConfigs.Add(new Bme680HeaterProfileConfig(profile, heaterResistance, duration));
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}
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/// <summary>
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/// Read the <see cref="Bme680PowerMode"/> state.
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/// </summary>
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/// <returns>The current <see cref="Bme680PowerMode"/>.</returns>
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public Bme680PowerMode ReadPowerMode()
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{
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var status = Read8BitsFromRegister((byte)Bme680Register.CTRL_MEAS);
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return (Bme680PowerMode)(status & (byte)Bme680Mask.PWR_MODE);
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}
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/// <summary>
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/// Gets the required time in ms to perform a measurement. The duration of the gas
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/// measurement is not considered if <see cref="GasConversionIsEnabled"/> is set to false
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/// or the chosen <see cref="Bme680HeaterProfile"/> is not configured.
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/// The precision of this duration is within 1ms of the actual measurement time.
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/// </summary>
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/// <param name="profile">The used <see cref="Bme680HeaterProfile"/>. </param>
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/// <returns></returns>
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public int GetMeasurementDuration(Bme680HeaterProfile profile)
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{
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var measCycles = s_osToMeasCycles[(int)TemperatureSampling];
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measCycles += s_osToMeasCycles[(int)PressureSampling];
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measCycles += s_osToMeasCycles[(int)HumiditySampling];
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var switchCount = s_osToSwitchCount[(int)TemperatureSampling];
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switchCount += s_osToSwitchCount[(int)PressureSampling];
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switchCount += s_osToSwitchCount[(int)HumiditySampling];
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double measDuration = measCycles * 1963;
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measDuration += 477 * switchCount; // TPH switching duration
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if (GasConversionIsEnabled)
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{
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measDuration += 477 * 5; // Gas measurement duration
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}
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measDuration += 500; // get it to the closest whole number
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measDuration /= 1000.0; // convert to ms
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measDuration += 1; // wake up duration of 1ms
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if (GasConversionIsEnabled && _heaterConfigs.Exists(config => config.HeaterProfile == profile))
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{
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measDuration += _heaterConfigs.Single(config => config.HeaterProfile == profile).HeaterDuration;
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}
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return (int)Math.Ceiling(measDuration);
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}
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/// <summary>
|
|||
|
|
/// Reads the humidity. A return value indicates whether the reading succeeded.
|
|||
|
|
/// </summary>
|
|||
|
|
/// <param name="humidity">
|
|||
|
|
/// Contains the measured humidity as %rH if the <see cref="HumiditySampling"/> was not set to <see cref="Sampling.Skipped"/>.
|
|||
|
|
/// Contains <see cref="double.NaN"/> otherwise.
|
|||
|
|
/// </param>
|
|||
|
|
/// <returns><code>true</code> if measurement was not skipped, otherwise <code>false</code>.</returns>
|
|||
|
|
public bool TryReadHumidity(out double humidity)
|
|||
|
|
{
|
|||
|
|
if (HumiditySampling == Sampling.Skipped)
|
|||
|
|
{
|
|||
|
|
humidity = double.NaN;
|
|||
|
|
return false;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Read humidity data.
|
|||
|
|
var hum = Read16BitsFromRegister((byte)Bme680Register.HUMIDITYDATA, Endianness.BigEndian);
|
|||
|
|
|
|||
|
|
TryReadTemperature(out _);
|
|||
|
|
humidity = CompensateHumidity(hum);
|
|||
|
|
return true;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>
|
|||
|
|
/// Reads the pressure. A return value indicates whether the reading succeeded.
|
|||
|
|
/// </summary>
|
|||
|
|
/// <param name="pressure">
|
|||
|
|
/// Contains the measured pressure if the <see cref="Bmxx80Base.PressureSampling"/> was not set to <see cref="Sampling.Skipped"/>.
|
|||
|
|
/// Contains <see cref="double.NaN"/> otherwise.
|
|||
|
|
/// </param>
|
|||
|
|
/// <returns><code>true</code> if measurement was not skipped, otherwise <code>false</code>.</returns>
|
|||
|
|
public override bool TryReadPressure(out Pressure pressure)
|
|||
|
|
{
|
|||
|
|
if (PressureSampling == Sampling.Skipped)
|
|||
|
|
{
|
|||
|
|
pressure = Pressure.FromPascal(double.NaN);
|
|||
|
|
return false;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Read pressure data.
|
|||
|
|
var press = (int)Read24BitsFromRegister((byte)Bme680Register.PRESSUREDATA, Endianness.BigEndian);
|
|||
|
|
|
|||
|
|
// Read the temperature first to load the t_fine value for compensation.
|
|||
|
|
TryReadTemperature(out _);
|
|||
|
|
|
|||
|
|
pressure = CompensatePressure(press >> 4);
|
|||
|
|
return true;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>
|
|||
|
|
/// Reads the temperature. A return value indicates whether the reading succeeded.
|
|||
|
|
/// </summary>
|
|||
|
|
/// <param name="temperature">
|
|||
|
|
/// Contains the measured temperature if the <see cref="Bmxx80Base.TemperatureSampling"/> was not set to <see cref="Sampling.Skipped"/>.
|
|||
|
|
/// Contains <see cref="double.NaN"/> otherwise.
|
|||
|
|
/// </param>
|
|||
|
|
/// <returns><code>true</code> if measurement was not skipped, otherwise <code>false</code>.</returns>
|
|||
|
|
public override bool TryReadTemperature(out Temperature temperature)
|
|||
|
|
{
|
|||
|
|
if (TemperatureSampling == Sampling.Skipped)
|
|||
|
|
{
|
|||
|
|
temperature = Temperature.FromCelsius(double.NaN);
|
|||
|
|
return false;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
var temp = (int)Read24BitsFromRegister((byte)Bme680Register.TEMPDATA, Endianness.BigEndian);
|
|||
|
|
|
|||
|
|
temperature = CompensateTemperature(temp >> 4);
|
|||
|
|
return true;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>
|
|||
|
|
/// Reads the gas resistance. A return value indicates whether the reading succeeded.
|
|||
|
|
/// </summary>
|
|||
|
|
/// <param name="gasResistance">
|
|||
|
|
/// Contains the measured gas resistance in Ohm if the heater module reached the target temperature and
|
|||
|
|
/// the measurement was valid. Contains <see cref="double.NaN"/> otherwise.
|
|||
|
|
/// </param>
|
|||
|
|
/// <returns><code>true</code> if measurement was not skipped, otherwise <code>false</code>.</returns>
|
|||
|
|
public bool TryReadGasResistance(out double gasResistance)
|
|||
|
|
{
|
|||
|
|
if (!ReadGasMeasurementIsValid() || !ReadHeaterIsStable())
|
|||
|
|
{
|
|||
|
|
gasResistance = double.NaN;
|
|||
|
|
return false;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// Read 10 bit gas resistance value from registers
|
|||
|
|
var gasResRaw = Read8BitsFromRegister((byte)Bme680Register.GAS_RES);
|
|||
|
|
var gasRange = Read8BitsFromRegister((byte)Bme680Register.GAS_RANGE);
|
|||
|
|
|
|||
|
|
var gasRes = (ushort)((ushort)(gasResRaw << 2) + (byte)(gasRange >> 6));
|
|||
|
|
gasRange &= (byte)Bme680Mask.GAS_RANGE;
|
|||
|
|
|
|||
|
|
gasResistance = CalculateGasResistance(gasRes, gasRange);
|
|||
|
|
return true;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>
|
|||
|
|
/// Sets the default configuration for the sensor.
|
|||
|
|
/// </summary>
|
|||
|
|
protected override void SetDefaultConfiguration()
|
|||
|
|
{
|
|||
|
|
base.SetDefaultConfiguration();
|
|||
|
|
HumiditySampling = Sampling.UltraLowPower;
|
|||
|
|
FilterMode = Bme680FilteringMode.C0;
|
|||
|
|
|
|||
|
|
_bme680Calibration = (Bme680CalibrationData)_calibrationData;
|
|||
|
|
TryReadTemperature(out var temp);
|
|||
|
|
ConfigureHeatingProfile(Bme680HeaterProfile.Profile1, 320, 150, temp.Celsius);
|
|||
|
|
HeaterProfile = Bme680HeaterProfile.Profile1;
|
|||
|
|
|
|||
|
|
HeaterIsEnabled = true;
|
|||
|
|
GasConversionIsEnabled = true;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>
|
|||
|
|
/// Compensates the humidity.
|
|||
|
|
/// </summary>
|
|||
|
|
/// <param name="adcHumidity">The humidity value read from the device.</param>
|
|||
|
|
/// <returns>The percentage relative humidity.</returns>
|
|||
|
|
private double CompensateHumidity(int adcHumidity)
|
|||
|
|
{
|
|||
|
|
// Calculate the humidity.
|
|||
|
|
var temperature = TemperatureFine / 5120.0;
|
|||
|
|
var var1 = adcHumidity - ((_bme680Calibration.DigH1 * 16.0) + ((_bme680Calibration.DigH3 / 2.0) * temperature));
|
|||
|
|
var var2 = var1 * ((_bme680Calibration.DigH2 / 262144.0) * (1.0 + ((_bme680Calibration.DigH4 / 16384.0) * temperature)
|
|||
|
|
+ ((_bme680Calibration.DigH5 / 1048576.0) * temperature * temperature)));
|
|||
|
|
var var3 = _bme680Calibration.DigH6 / 16384.0;
|
|||
|
|
var var4 = _bme680Calibration.DigH7 / 2097152.0;
|
|||
|
|
var calculatedHumidity = var2 + ((var3 + (var4 * temperature)) * var2 * var2);
|
|||
|
|
|
|||
|
|
if (calculatedHumidity > 100.0)
|
|||
|
|
{
|
|||
|
|
calculatedHumidity = 100.0;
|
|||
|
|
}
|
|||
|
|
else if (calculatedHumidity < 0.0)
|
|||
|
|
{
|
|||
|
|
calculatedHumidity = 0.0;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return calculatedHumidity;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// <summary>
|
|||
|
|
/// Compensates the pressure.
|
|||
|
|
/// </summary>
|
|||
|
|
/// <param name="adcPressure">The pressure value read from the device.</param>
|
|||
|
|
/// <returns>The pressure in Pa.</returns>
|
|||
|
|
private Pressure CompensatePressure(long adcPressure)
|
|||
|
|
{
|
|||
|
|
// Calculate the pressure.
|
|||
|
|
var var1 = (TemperatureFine / 2.0) - 64000.0;
|
|||
|
|
var var2 = var1 * var1 * (_bme680Calibration.DigP6 / 131072.0);
|
|||
|
|
var2 += (var1 * _bme680Calibration.DigP5 * 2.0);
|
|||
|
|
var2 = (var2 / 4.0) + (_bme680Calibration.DigP4 * 65536.0);
|
|||
|
|
var1 = ((_bme680Calibration.DigP3 * var1 * var1 / 16384.0) + (_bme680Calibration.DigP2 * var1)) / 524288.0;
|
|||
|
|
var1 = (1.0 + (var1 / 32768.0)) * _bme680Calibration.DigP1;
|
|||
|
|
var calculatedPressure = 1048576.0 - adcPressure;
|
|||
|
|
|
|||
|
|
// Avoid exception caused by division by zero.
|
|||
|
|
if (var1 != 0)
|
|||
|
|
{
|
|||
|
|
calculatedPressure = (calculatedPressure - (var2 / 4096.0)) * 6250.0 / var1;
|
|||
|
|
var1 = _bme680Calibration.DigP9 * calculatedPressure * calculatedPressure / 2147483648.0;
|
|||
|
|
var2 = calculatedPressure * (_bme680Calibration.DigP8 / 32768.0);
|
|||
|
|
var var3 = (calculatedPressure / 256.0) * (calculatedPressure / 256.0) * (calculatedPressure / 256.0)
|
|||
|
|
* (_bme680Calibration.DigP10 / 131072.0);
|
|||
|
|
calculatedPressure += (var1 + var2 + var3 + (_bme680Calibration.DigP7 * 128.0)) / 16.0;
|
|||
|
|
}
|
|||
|
|
else
|
|||
|
|
{
|
|||
|
|
calculatedPressure = 0;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return Pressure.FromPascal(calculatedPressure);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
private bool ReadGasMeasurementIsValid()
|
|||
|
|
{
|
|||
|
|
var gasMeasValid = Read8BitsFromRegister((byte)Bme680Register.GAS_RANGE);
|
|||
|
|
gasMeasValid = (byte)((gasMeasValid & (byte)Bme680Mask.GAS_VALID) >> 5);
|
|||
|
|
|
|||
|
|
return Convert.ToBoolean(gasMeasValid);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
private double CalculateGasResistance(ushort adcGasRes, byte gasRange)
|
|||
|
|
{
|
|||
|
|
var var1 = 1340.0 + 5.0 * _bme680Calibration.RangeSwErr;
|
|||
|
|
var var2 = var1 * (1.0 + s_k1Lookup[gasRange] / 100.0);
|
|||
|
|
var var3 = 1.0 + s_k2Lookup[gasRange] / 100.0;
|
|||
|
|
var gasResistance = 1.0 / (var3 * 0.000000125 * (1 << gasRange) * ((adcGasRes - 512.0) / var2 + 1.0));
|
|||
|
|
|
|||
|
|
return gasResistance;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
private byte CalculateHeaterResistance(ushort setTemp, short ambientTemp)
|
|||
|
|
{
|
|||
|
|
// limit maximum temperature to 400°C
|
|||
|
|
if (setTemp > 400)
|
|||
|
|
{
|
|||
|
|
setTemp = 400;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
var var1 = _bme680Calibration.DigGh1 / 16.0 + 49.0;
|
|||
|
|
var var2 = _bme680Calibration.DigGh2 / 32768.0 * 0.0005 + 0.00235;
|
|||
|
|
var var3 = _bme680Calibration.DigGh3 / 1024.0;
|
|||
|
|
var var4 = var1 * (1.0 + var2 * setTemp);
|
|||
|
|
var var5 = var4 + var3 * ambientTemp;
|
|||
|
|
var heaterResistance = (byte)(3.4 * (var5 * (4.0 / (4.0 + _bme680Calibration.ResHeatRange)) * (1.0 / (1.0 + _bme680Calibration.ResHeatVal * 0.002)) - 25));
|
|||
|
|
|
|||
|
|
return heaterResistance;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// The duration is interpreted as follows:
|
|||
|
|
// Byte [7:6]: multiplication factor of 1, 4, 16 or 64
|
|||
|
|
// Byte [5:0]: 64 timer values, 1ms step size
|
|||
|
|
// Values are rounded down
|
|||
|
|
private byte CalculateHeaterDuration(ushort duration)
|
|||
|
|
{
|
|||
|
|
byte factor = 0;
|
|||
|
|
byte durationValue;
|
|||
|
|
|
|||
|
|
// check if value exceeds maximum duration
|
|||
|
|
if (duration > 0xFC0)
|
|||
|
|
{
|
|||
|
|
durationValue = 0xFF;
|
|||
|
|
}
|
|||
|
|
else
|
|||
|
|
{
|
|||
|
|
while (duration > 0x3F)
|
|||
|
|
{
|
|||
|
|
duration = (ushort)(duration >> 2);
|
|||
|
|
factor += 1;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
durationValue = (byte)(duration + factor * 64);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
return durationValue;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|