/// <summary>
/// Get a reading from the sensor and set the Temperature and Humidity properties.
/// </summary>
public void Update()
{
var data = _sht31d.WriteRead(new byte[] { 0x2c, 0x06 }, 6);
Humidity = (100 * (float)((data[3] << 8) + data[4])) / 65535;
Temperature = ((175 * (float)((data[0] << 8) + data[1])) / 65535) - 45;
}
/// <summary>
/// Create a new SI7021 temperature and humidity sensor.
/// </summary>
/// <param name="address">Sensor address (default to 0x40).</param>
/// <param name="speed">Speed of the I2C interface (default to 100 KHz).</param>
/// <param name="updateInterval">Number of milliseconds between samples (0 indicates polling to be used)</param>
/// <param name="humidityChangeNotificationThreshold">Changes in humidity greater than this value will trigger an event when updatePeriod > 0.</param>
/// <param name="temperatureChangeNotificationThreshold">Changes in temperature greater than this value will trigger an event when updatePeriod > 0.</param>
public SI7021(byte address = 0x40, ushort speed = 100, ushort updateInterval = MinimumPollingPeriod,
float humidityChangeNotificationThreshold = 0.001F, float temperatureChangeNotificationThreshold = 0.001F)
{
if (speed > 1000)
{
throw new ArgumentOutOfRangeException(nameof(speed), "Speed should be between 0 and 1000 KHz");
}
if (humidityChangeNotificationThreshold < 0)
{
throw new ArgumentOutOfRangeException(nameof(humidityChangeNotificationThreshold), "Humidity threshold should be >= 0");
}
if (temperatureChangeNotificationThreshold < 0)
{
throw new ArgumentOutOfRangeException(nameof(temperatureChangeNotificationThreshold), "Temperature threshold should be >= 0");
}
if ((updateInterval != 0) && (updateInterval < MinimumPollingPeriod))
{
throw new ArgumentOutOfRangeException(nameof(updateInterval), "Update period should be 0 or >= than " + MinimumPollingPeriod);
}
TemperatureChangeNotificationThreshold = temperatureChangeNotificationThreshold;
HumidityChangeNotificationThreshold = humidityChangeNotificationThreshold;
_updateInterval = updateInterval;
_si7021 = new I2cBus(address, speed);
//
// Get the device ID.
//
var part1 = _si7021.WriteRead(new[]
{
Registers.ReadIDFirstBytePart1,
Registers.ReadIDFirstBytePart2
}, 8);
var part2 = _si7021.WriteRead(new[]
{
Registers.ReadIDSecondBytePart1,
Registers.ReadIDSecondBytePart2
}, 6);
SerialNumber = 0;
for (var index = 0; index < 4; index++)
{
SerialNumber <<= 8;
SerialNumber += part1[index * 2];
}
SerialNumber <<= 8;
SerialNumber += part2[0];
SerialNumber <<= 8;
SerialNumber += part2[1];
SerialNumber <<= 8;
SerialNumber += part2[3];
SerialNumber <<= 8;
SerialNumber += part2[4];
if ((part2[0] == 0) || (part2[0] == 0xff))
{
SensorType = DeviceType.EngineeringSample;
}
else
{
SensorType = (DeviceType)part2[0];
}
//
// Update the firmware revision.
//
var firmware = _si7021.WriteRead(new[]
{
Registers.ReadFirmwareRevisionPart1,
Registers.ReadFirmwareRevisionPart2
}, 1);
FirmwareRevision = firmware[0];
if (updateInterval > 0)
{
StartUpdating();
}
else
{
Update();
}
}
