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commonMain.devices.bosch.Bme280.kt Maven / Gradle / Ivy
@file:OptIn(ExperimentalUnsignedTypes::class)
@file:Suppress("SpellCheckingInspection")
package ch.softappeal.konapi.devices.bosch
import ch.softappeal.konapi.I2cDevice
import ch.softappeal.konapi.sleepMs
/*
Combined digital humidity, pressure and temperature sensor
Datasheet: https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bme280-ds002.pdf
API : https://github.com/boschsensortec/BME280_SensorAPI/blob/master/bme280.c
*/
private class TemperatureCalib(
val t1: Double,
val t2: Double,
val t3: Double,
)
private class PressureCalib(
val p1: Double,
val p2: Double,
val p3: Double,
val p4: Double,
val p5: Double,
val p6: Double,
val p7: Double,
val p8: Double,
val p9: Double,
)
private class HumidityCalib(
val h1: Double,
val h2: Double,
val h3: Double,
val h4: Double,
val h5: Double,
val h6: Double,
)
private data class TemperatureCompensateResult(val temperaturInCelsius: Double, val tFine: Double)
private fun TemperatureCalib.compensate(t: Double): TemperatureCompensateResult {
// API: compensate_temperature
val var1 = (t / 16_384.0 - t1 / 1024.0) * t2
var var2 = t / 131_072.0 - t1 / 8192.0
var2 *= var2 * t3
val tFine = var1 + var2
return TemperatureCompensateResult(temperaturInCelsius = (tFine / 5120.0).coerceIn(-40.0, 85.0), tFine)
}
private fun PressureCalib.compensate(p: Double, tFine: Double): Double {
// API: compensate_pressure
var var1 = tFine / 2.0 - 64_000.0
var var2 = var1 * var1 * p6 / 32_768.0
var2 += var1 * p5 * 2.0
var2 = var2 / 4.0 + p4 * 65_536.0
val var3 = p3 * var1 * var1 / 524_288.0
var1 = (var3 + p2 * var1) / 524_288.0
var1 = (1.0 + var1 / 32_768.0) * p1
return if (var1 <= 0.0) 30_000.0 else {
var pressure = 1048_576.0 - p
pressure = (pressure - var2 / 4096.0) * 6250.0 / var1
var1 = p9 * pressure * pressure / 2147_483_648.0
var2 = pressure * p8 / 32_768.0
pressure += (var1 + var2 + p7) / 16.0
pressure.coerceIn(30_000.0, 110_000.0)
}
}
private fun HumidityCalib.compensate(h: Double, tFine: Double): Double {
// API: compensate_humidity
val var1 = tFine - 76_800.0
val var2 = h4 * 64.0 + h5 / 16_384.0 * var1
val var3 = h - var2
val var4 = h2 / 65_536.0
val var5 = 1.0 + h3 / 67_108_864.0 * var1
var var6 = 1.0 + h6 / 67_108_864.0 * var1 * var5
var6 *= var3 * var4 * var5
return (var6 * (1.0 - h1 * var6 / 524_288.0)).coerceIn(0.0, 100.0)
}
public class Bme280(private val device: I2cDevice) {
private val temperatureCalib: TemperatureCalib
private val pressureCalib: PressureCalib
private val humidityCalib: HumidityCalib
private fun setupMode() {
/*
Datasheet:
Table 7: Settings and performance for weather monitoring
5.4.3 Register 0xF2 "ctrl_hum"
Changes to this register only become effective after a write operation to "ctrl_meas".
5.4.5 Register 0xF4 "ctrl_meas"
*/
device.write(
0xF2U, // ctrl_hum
0x01U // Humidity oversampling x1
)
device.write(
0xF4U, // ctrl_meas
0x01U.toUByte() or // Forced mode
0x04U or // Pressure oversampling x1
0x20U // Temperature oversampling x1
)
}
init {
device.write(0xE0U, 0xB6U) // reset
sleepMs(300) // power-on delay
check(device.read(0xD0U) == 0x60U.toUByte()) { "chipId isn't BME280" }
setupMode()
/*
Datasheet:
4.2.2 Trimming parameter readout:
The trimming parameters are programmed into the devices non-volatile memory (NVM) during
production and cannot be altered by the customer.
Table 16: Compensation parameter storage, naming and data type
Table 18: Memory map
API:
parse_temp_press_calib_data
parse_humidity_calib_data
*/
fun UByteArray.toShort(offset: Int) = ((this[offset + 1].toByte().toInt() shl 8) or this[offset].toInt()).toDouble()
fun UByteArray.toUShort(offset: Int) = ((this[offset + 1].toInt() shl 8) or this[offset].toInt()).toDouble()
val h1: Double
with(device.read(0x88U, 26)) { // calib00to25
temperatureCalib = TemperatureCalib(
t1 = toUShort(0),
t2 = toShort(2),
t3 = toShort(4),
)
pressureCalib = PressureCalib(
p1 = toUShort(6),
p2 = toShort(8),
p3 = toShort(10),
p4 = toShort(12),
p5 = toShort(14),
p6 = toShort(16),
p7 = toShort(18),
p8 = toShort(20),
p9 = toShort(22),
)
h1 = this[25].toInt().toDouble()
}
humidityCalib = with(device.read(0xE1U, 7)) { // calib26to32
HumidityCalib(
h1 = h1,
h2 = toShort(0),
h3 = this[2].toInt().toDouble(),
h4 = ((this[3].toByte().toInt() shl 4) or (this[4].toInt() and 0x0F)).toDouble(),
h5 = ((this[5].toByte().toInt() shl 4) or (this[4].toInt() shr 4)).toDouble(),
h6 = this[6].toByte().toInt().toDouble(),
)
}
}
public data class Measurement(
public val temperaturInCelsius: Double,
public val pressureInPascal: Double,
public val humidityInPercent: Double,
)
public fun measurement(): Measurement {
setupMode()
/*
Datasheet:
4. Data readout
Table 29: Register 0xF7 ... 0xF9 "press"
Table 30: Register 0xFA ... 0xFC "temp"
Table 31: Register 0xFD ... 0xFE "hum"
Table 18: Memory map
API: parse_sensor_data
*/
val adc = device.read(0xF7U, 8)
fun toUShort(offset: Int) =
((adc[offset].toInt() shl 12) or (adc[offset + 1].toInt() shl 4) or (adc[offset + 2].toInt() shr 4)).toDouble()
val (temperaturInCelsius, tFine) = temperatureCalib.compensate(toUShort(3))
return Measurement(
temperaturInCelsius = temperaturInCelsius,
pressureInPascal = pressureCalib.compensate(toUShort(0), tFine),
humidityInPercent = humidityCalib.compensate(((adc[6].toInt() shl 8) or adc[7].toInt()).toDouble(), tFine)
)
}
}
