299 lines
13 KiB
C#
299 lines
13 KiB
C#
// 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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// Ported from https://github.com/adafruit/Adafruit_BMP280_Library/blob/master/Adafruit_BMP280.cpp
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// Formulas and code examples can also be found in the datasheet http://www.adafruit.com/datasheets/BST-BMP280-DS001-11.pdf
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using System;
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using System.Device.I2c;
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using System.IO;
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using NucuCar.Sensors.Environment.Bmxx80.FilteringMode;
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using NucuCar.Sensors.Environment.Bmxx80.Register;
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using NucuCar.Sensors.Environment.Bmxx80.Units;
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using Bmx280PowerMode = NucuCar.Sensors.Environment.Bmxx80.PowerMode.Bmx280PowerMode;
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namespace NucuCar.Sensors.Environment.Bmxx80
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{
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/// <summary>
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/// Represents the core functionality of the Bmx280 family.
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/// </summary>
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public abstract class Bmx280Base : NucuCar.Sensors.Environment.Bmxx80.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 = 0x77;
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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 = 0x76;
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/// <summary>
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/// Converts oversampling to needed measurement cycles for that oversampling.
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/// </summary>
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protected static readonly int[] s_osToMeasCycles = { 0, 7, 9, 14, 23, 44 };
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private Bmx280FilteringMode _filteringMode;
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private NucuCar.Sensors.Environment.Bmxx80.StandbyTime _standbyTime;
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/// <summary>
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/// Initializes a new instance of the <see cref="Bmx280Base"/> class.
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/// </summary>
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/// <param name="deviceId">The ID of the device.</param>
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/// <param name="i2cDevice">The <see cref="I2cDevice"/> to create with.</param>
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protected Bmx280Base(byte deviceId, I2cDevice i2cDevice)
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: base(deviceId, i2cDevice)
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{
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}
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/// <summary>
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/// Gets or sets the IIR filter mode.
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/// </summary>
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/// <exception cref="ArgumentOutOfRangeException">Thrown when the <see cref="Bmx280FilteringMode"/> is set to an undefined mode.</exception>
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public Bmx280FilteringMode FilterMode
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{
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get => _filteringMode;
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set
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{
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byte current = Read8BitsFromRegister((byte)Bmx280Register.CONFIG);
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current = (byte)((current & 0b_1110_0011) | (byte)value << 2);
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Span<byte> command = stackalloc[]
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{
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(byte)Bmx280Register.CONFIG, current
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};
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_i2cDevice.Write(command);
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_filteringMode = value;
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}
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}
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/// <summary>
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/// Gets or sets the standby time between two consecutive measurements.
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/// </summary>
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/// <exception cref="ArgumentOutOfRangeException">Thrown when the <see cref="NucuCar.Sensors.Environment.Bmxx80.StandbyTime"/> is set to an undefined mode.</exception>
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public NucuCar.Sensors.Environment.Bmxx80.StandbyTime StandbyTime
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{
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get => _standbyTime;
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set
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{
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byte current = Read8BitsFromRegister((byte)Bmx280Register.CONFIG);
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current = (byte)((current & 0b_0001_1111) | (byte)value << 5);
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Span<byte> command = stackalloc[]
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{
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(byte)Bmx280Register.CONFIG, current
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};
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_i2cDevice.Write(command);
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_standbyTime = value;
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}
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}
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/// <summary>
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/// Reads the temperature. A return value indicates whether the reading succeeded.
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/// </summary>
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/// <param name="temperature">
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/// Contains the measured temperature if the <see cref="NucuCar.Sensors.Environment.Bmxx80.Bmxx80Base.TemperatureSampling"/> was not set to <see cref="NucuCar.Sensors.Environment.Bmxx80.Sampling.Skipped"/>.
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/// Contains <see cref="double.NaN"/> otherwise.
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/// </param>
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/// <returns><code>true</code> if measurement was not skipped, otherwise <code>false</code>.</returns>
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public override bool TryReadTemperature(out Temperature temperature)
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{
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if (TemperatureSampling == NucuCar.Sensors.Environment.Bmxx80.Sampling.Skipped)
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{
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temperature = Temperature.FromCelsius(double.NaN);
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return false;
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}
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var temp = (int)Read24BitsFromRegister((byte)Bmx280Register.TEMPDATA_MSB, Endianness.BigEndian);
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temperature = CompensateTemperature(temp >> 4);
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return true;
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}
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/// <summary>
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/// Read the <see cref="Bmx280PowerMode"/> state.
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/// </summary>
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/// <returns>The current <see cref="Bmx280PowerMode"/>.</returns>
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/// <exception cref="NotImplementedException">Thrown when the power mode does not match a defined mode in <see cref="Bmx280PowerMode"/>.</exception>
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public Bmx280PowerMode ReadPowerMode()
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{
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byte read = Read8BitsFromRegister(_controlRegister);
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// Get only the power mode bits.
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var powerMode = (byte)(read & 0b_0000_0011);
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if (Enum.IsDefined(typeof(Bmx280PowerMode), powerMode) == false)
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{
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throw new IOException("Read unexpected power mode");
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}
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return powerMode switch
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{
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0b00 => Bmx280PowerMode.Sleep,
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0b10 => Bmx280PowerMode.Forced,
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0b11 => Bmx280PowerMode.Normal,
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_ => throw new NotImplementedException($"Read power mode not defined by specification.")
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};
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}
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/// <summary>
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/// Reads the pressure. A return value indicates whether the reading succeeded.
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/// </summary>
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/// <param name="pressure">
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/// Contains the measured pressure in Pa if the <see cref="NucuCar.Sensors.Environment.Bmxx80.Bmxx80Base.PressureSampling"/> was not set to <see cref="NucuCar.Sensors.Environment.Bmxx80.Sampling.Skipped"/>.
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/// Contains <see cref="double.NaN"/> otherwise.
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/// </param>
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/// <returns><code>true</code> if measurement was not skipped, otherwise <code>false</code>.</returns>
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public override bool TryReadPressure(out Pressure pressure)
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{
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if (PressureSampling == NucuCar.Sensors.Environment.Bmxx80.Sampling.Skipped)
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{
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pressure = Pressure.FromPascal(double.NaN);
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return false;
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}
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// Read the temperature first to load the t_fine value for compensation.
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TryReadTemperature(out _);
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// Read pressure data.
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var press = (int)Read24BitsFromRegister((byte)Bmx280Register.PRESSUREDATA, Endianness.BigEndian);
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// Convert the raw value to the pressure in Pa.
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var pressPa = CompensatePressure(press >> 4);
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// Return the pressure as a Pressure instance.
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pressure = Pressure.FromHectopascal(pressPa.Hectopascal / 256);
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return true;
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}
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/// <summary>
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/// Calculates the altitude in meters from the specified sea-level pressure(in hPa).
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/// </summary>
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/// <param name="seaLevelPressure">Sea-level pressure</param>
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/// <param name="altitude">
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/// Contains the calculated metres above sea-level if the <see cref="NucuCar.Sensors.Environment.Bmxx80.Bmxx80Base.PressureSampling"/> was not set to <see cref="NucuCar.Sensors.Environment.Bmxx80.Sampling.Skipped"/>.
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/// Contains <see cref="double.NaN"/> otherwise.
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/// </param>
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/// <returns><code>true</code> if pressure measurement was not skipped, otherwise <code>false</code>.</returns>
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public bool TryReadAltitude(Pressure seaLevelPressure, out double altitude)
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{
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// Read the pressure first.
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var success = TryReadPressure(out var pressure);
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if (!success)
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{
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altitude = double.NaN;
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return false;
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}
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// Calculate and return the altitude using the international barometric formula.
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altitude = 44330.0 * (1.0 - Math.Pow(pressure.Hectopascal / seaLevelPressure.Hectopascal, 0.1903));
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return true;
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}
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/// <summary>
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/// Calculates the altitude in meters from the mean sea-level pressure.
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/// </summary>
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/// <param name="altitude">
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/// Contains the calculated metres above sea-level if the <see cref="NucuCar.Sensors.Environment.Bmxx80.Bmxx80Base.PressureSampling"/> was not set to <see cref="NucuCar.Sensors.Environment.Bmxx80.Sampling.Skipped"/>.
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/// Contains <see cref="double.NaN"/> otherwise.
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/// </param>
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/// <returns><code>true</code> if pressure measurement was not skipped, otherwise <code>false</code>.</returns>
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public bool TryReadAltitude(out double altitude)
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{
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return TryReadAltitude(Pressure.MeanSeaLevel, out altitude);
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}
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/// <summary>
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/// Get the current status of the device.
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/// </summary>
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/// <returns>The <see cref="NucuCar.Sensors.Environment.Bmxx80.DeviceStatus"/>.</returns>
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public NucuCar.Sensors.Environment.Bmxx80.DeviceStatus ReadStatus()
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{
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var status = Read8BitsFromRegister((byte)Bmx280Register.STATUS);
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// Bit 3.
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var measuring = ((status >> 3) & 1) == 1;
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// Bit 0.
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var imageUpdating = (status & 1) == 1;
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return new NucuCar.Sensors.Environment.Bmxx80.DeviceStatus
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{
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ImageUpdating = imageUpdating,
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Measuring = measuring
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};
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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="Bmx280PowerMode"/> to set.</param>
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public void SetPowerMode(Bmx280PowerMode powerMode)
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{
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byte read = Read8BitsFromRegister(_controlRegister);
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// Clear last 2 bits.
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var cleared = (byte)(read & 0b_1111_1100);
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Span<byte> command = stackalloc[]
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{
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_controlRegister, (byte)(cleared | (byte)powerMode)
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};
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_i2cDevice.Write(command);
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}
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/// <summary>
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/// Gets the required time in ms to perform a measurement with the current sampling modes.
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/// </summary>
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/// <returns>The time it takes for the chip to read data in milliseconds rounded up.</returns>
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public virtual int GetMeasurementDuration()
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{
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return s_osToMeasCycles[(int)PressureSampling] + s_osToMeasCycles[(int)TemperatureSampling];
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}
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/// <summary>
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/// Sets the default configuration for the sensor.
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/// </summary>
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protected override void SetDefaultConfiguration()
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{
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base.SetDefaultConfiguration();
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FilterMode = Bmx280FilteringMode.Off;
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StandbyTime = NucuCar.Sensors.Environment.Bmxx80.StandbyTime.Ms125;
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}
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/// <summary>
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/// Compensates the pressure in Pa, in Q24.8 format (24 integer bits and 8 fractional bits).
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/// </summary>
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/// <param name="adcPressure">The pressure value read from the device.</param>
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/// <returns>Pressure in Hectopascals (hPa).</returns>
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/// <remarks>
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/// Output value of “24674867” represents 24674867/256 = 96386.2 Pa = 963.862 hPa.
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/// </remarks>
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private Pressure CompensatePressure(long adcPressure)
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{
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// Formula from the datasheet http://www.adafruit.com/datasheets/BST-BMP280-DS001-11.pdf
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// The pressure is calculated using the compensation formula in the BMP280 datasheet
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long var1 = TemperatureFine - 128000;
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long var2 = var1 * var1 * (long)_calibrationData.DigP6;
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var2 = var2 + ((var1 * (long)_calibrationData.DigP5) << 17);
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var2 = var2 + ((long)_calibrationData.DigP4 << 35);
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var1 = ((var1 * var1 * (long)_calibrationData.DigP3) >> 8) + ((var1 * (long)_calibrationData.DigP2) << 12);
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var1 = ((((1L << 47) + var1)) * (long)_calibrationData.DigP1) >> 33;
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if (var1 == 0)
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{
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return Pressure.FromPascal(0); // Avoid exception caused by division by zero
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}
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// Perform calibration operations
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long p = 1048576 - adcPressure;
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p = (((p << 31) - var2) * 3125) / var1;
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var1 = ((long)_calibrationData.DigP9 * (p >> 13) * (p >> 13)) >> 25;
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var2 = ((long)_calibrationData.DigP8 * p) >> 19;
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p = ((p + var1 + var2) >> 8) + ((long)_calibrationData.DigP7 << 4);
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return Pressure.FromPascal(p);
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}
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}
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}
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