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https://github.com/tinygo-org/drivers.git
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bme280: improve config support
This commit is contained in:
Kenneth Bell
Ron Evans
+115
-5
@@ -7,6 +7,7 @@ package bme280
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import (
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"math"
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"time"
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"tinygo.org/x/drivers"
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)
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@@ -33,11 +34,27 @@ type calibrationCoefficients struct {
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h6 int8
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}
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type Oversampling byte
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type Mode byte
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type FilterCoefficient byte
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type Period byte
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// Config contains settings for filtering, sampling, and modes of operation
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type Config struct {
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Pressure Oversampling
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Temperature Oversampling
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Humidity Oversampling
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Period Period
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Mode Mode
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IIR FilterCoefficient
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}
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// Device wraps an I2C connection to a BME280 device.
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type Device struct {
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bus drivers.I2C
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Address uint16
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calibrationCoefficients calibrationCoefficients
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Config Config
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}
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// New creates a new BME280 connection. The I2C bus must already be
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@@ -51,9 +68,34 @@ func New(bus drivers.I2C) Device {
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}
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}
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// Configure sets up the device for communication and
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// read the calibration coefficientes.
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// ConfigureWithSettings sets up the device for communication and
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// read the calibration coefficients.
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//
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// The default configuration is the Indoor Navigation settings
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// from the BME280 datasheet.
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func (d *Device) Configure() {
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d.ConfigureWithSettings(Config{})
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}
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// ConfigureWithSettings sets up the device for communication and
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// read the calibration coefficients.
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//
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// The default configuration if config is left at defaults is
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// the Indoor Navigation settings from the BME280 datasheet.
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func (d *Device) ConfigureWithSettings(config Config) {
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d.Config = config
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// If config is not initialized, use Indoor Navigation defaults.
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if d.Config == (Config{}) {
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d.Config = Config{
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Mode: ModeNormal,
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Period: Period0_5ms,
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Temperature: Sampling2X,
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Humidity: Sampling1X,
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Pressure: Sampling16X,
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IIR: Coeff16,
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}
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}
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var data [24]byte
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err := d.bus.ReadRegister(uint8(d.Address), REG_CALIBRATION, data[:])
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@@ -93,10 +135,18 @@ func (d *Device) Configure() {
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d.calibrationCoefficients.h4 = 0 + (int16(h2lsb[3]) << 4) | (int16(h2lsb[4] & 0x0F))
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d.calibrationCoefficients.h5 = 0 + (int16(h2lsb[5]) << 4) | (int16(h2lsb[4]) >> 4)
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d.bus.WriteRegister(uint8(d.Address), CTRL_HUMIDITY_ADDR, []byte{0x3f})
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d.bus.WriteRegister(uint8(d.Address), CTRL_MEAS_ADDR, []byte{0xB7})
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d.bus.WriteRegister(uint8(d.Address), CTRL_CONFIG, []byte{0x00})
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d.Reset()
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d.bus.WriteRegister(uint8(d.Address), CTRL_CONFIG, []byte{byte(d.Config.Period<<5) | byte(d.Config.IIR<<2)})
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d.bus.WriteRegister(uint8(d.Address), CTRL_HUMIDITY_ADDR, []byte{byte(d.Config.Humidity)})
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// Normal mode, start measuring now
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if d.Config.Mode == ModeNormal {
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d.bus.WriteRegister(uint8(d.Address), CTRL_MEAS_ADDR, []byte{
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byte(d.Config.Temperature<<5) |
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byte(d.Config.Pressure<<2) |
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byte(d.Config.Mode)})
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}
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}
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// Connected returns whether a BME280 has been found.
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@@ -112,6 +162,20 @@ func (d *Device) Reset() {
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d.bus.WriteRegister(uint8(d.Address), CMD_RESET, []byte{0xB6})
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}
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// SetMode can set the device to Sleep, Normal or Forced mode
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//
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// Calling this method is optional, Configure can be used to set the
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// initial mode if no mode change is desired. This method is most
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// useful to switch between Sleep and Normal modes.
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func (d *Device) SetMode(mode Mode) {
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d.Config.Mode = mode
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d.bus.WriteRegister(uint8(d.Address), CTRL_MEAS_ADDR, []byte{
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byte(d.Config.Temperature<<5) |
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byte(d.Config.Pressure<<2) |
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byte(d.Config.Mode)})
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}
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// ReadTemperature returns the temperature in celsius milli degrees (°C/1000)
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func (d *Device) ReadTemperature() (int32, error) {
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data, err := d.readData()
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@@ -186,6 +250,16 @@ func readIntLE(msb byte, lsb byte) int16 {
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// readData does a burst read from 0xF7 to 0xF0 according to the datasheet
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// resulting in an slice with 8 bytes 0-2 = pressure / 3-5 = temperature / 6-7 = humidity
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func (d *Device) readData() (data [8]byte, err error) {
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if d.Config.Mode == ModeForced {
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// Write the CTRL_MEAS register to trigger a measurement
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d.bus.WriteRegister(uint8(d.Address), CTRL_MEAS_ADDR, []byte{
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byte(d.Config.Temperature<<5) |
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byte(d.Config.Pressure<<2) |
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byte(d.Config.Mode)})
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time.Sleep(d.measurementDelay())
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}
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err = d.bus.ReadRegister(uint8(d.Address), REG_PRESSURE, data[:])
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if err != nil {
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println(err)
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@@ -256,3 +330,39 @@ func (d *Device) calculateHumidity(data [8]byte, tFine int32) int32 {
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return int32(100 * h)
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}
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// measurementDelay returns how much time each measurement will take
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// on the device.
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//
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// This is used in forced mode to wait until a measurement is complete.
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func (d *Device) measurementDelay() time.Duration {
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const MeasOffset = 1250
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const MeasDur = 2300
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const HumMeasOffset = 575
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const MeasScalingFactor = 1000
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// delay is based on over-sampling rate - this table converts from
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// setting to number samples
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sampleRateConv := []int{0, 1, 2, 4, 8, 16}
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tempOsr := 16
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if d.Config.Temperature <= Sampling16X {
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tempOsr = sampleRateConv[d.Config.Temperature]
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}
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presOsr := 16
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if d.Config.Temperature <= Sampling16X {
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presOsr = sampleRateConv[d.Config.Pressure]
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}
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humOsr := 16
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if d.Config.Temperature <= Sampling16X {
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humOsr = sampleRateConv[d.Config.Humidity]
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}
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max_delay := ((MeasOffset + (MeasDur * tempOsr) +
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((MeasDur * presOsr) + HumMeasOffset) +
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((MeasDur * humOsr) + HumMeasOffset)) / MeasScalingFactor)
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return time.Duration(max_delay) * time.Millisecond
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}
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@@ -20,6 +20,50 @@ const (
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CHIP_ID = 0x60
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)
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// Increasing sampling rate increases precision but also the wait time for measurements. The datasheet has a table of
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// suggested values for oversampling, output data rates, and iir filter coefficients by use case.
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const (
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SamplingOff Oversampling = iota
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Sampling1X
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Sampling2X
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Sampling4X
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Sampling8X
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Sampling16X
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)
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// In normal mode (the default) the sensor takes masurements periodically. In forced
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// mode, the sensor takes a measurement only when requested.
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//
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// For use-cases with infrequent sampling, forced mode is more power efficient.
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const (
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ModeNormal Mode = 0x03
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ModeForced Mode = 0x01
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ModeSleep Mode = 0x00
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)
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// IIR filter coefficients, higher values means steadier measurements but slower reaction times
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const (
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Coeff0 FilterCoefficient = iota
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Coeff2
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Coeff4
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Coeff8
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Coeff16
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)
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// Period of standby in normal mode which controls how often measurements are taken
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//
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// Note Period10ms and Period20ms are out of sequence, but are per the datasheet
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const (
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Period0_5ms Period = 0b000
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Period62_5ms = 0b001
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Period125ms = 0b010
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Period250ms = 0b011
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Period500ms = 0b100
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Period1000ms = 0b101
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Period10ms = 0b110
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Period20ms = 0b111
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)
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const (
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SEALEVEL_PRESSURE float32 = 1013.25 // in hPa
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)
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