mirror of
https://github.com/kidoman/embd
synced 2024-11-13 04:58:55 +01:00
123 lines
2.6 KiB
Go
123 lines
2.6 KiB
Go
// Package BH1750FVI allows interfacing with the BH1750FVI ambient light sensor through I2C.
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package bh1750fvi
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import (
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"sync"
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"time"
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"github.com/kidoman/embd"
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)
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//accuracy = sensorValue/actualValue] (min = 0.96, typ = 1.2, max = 1.44
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const (
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High = "H"
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High2 = "H2"
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measurementAcuuracy = 1.2
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defReadReg = 0x00
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sensorI2cAddr = 0x23
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highResOpCode = 0x10
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highResMode2OpCode = 0x11
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pollDelay = 150
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)
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// BH1750FVI represents a BH1750FVI ambient light sensor.
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type BH1750FVI struct {
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Bus embd.I2CBus
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Poll int
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mu sync.RWMutex
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lightingReadings chan float64
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quit chan bool
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i2cAddr byte
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operationCode byte
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}
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// New returns a BH1750FVI sensor at the specific resolution mode.
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func New(mode string, bus embd.I2CBus) *BH1750FVI {
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switch mode {
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case High:
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return &BH1750FVI{Bus: bus, i2cAddr: sensorI2cAddr, operationCode: highResOpCode, Poll: pollDelay}
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case High2:
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return &BH1750FVI{Bus: bus, i2cAddr: sensorI2cAddr, operationCode: highResMode2OpCode, Poll: pollDelay}
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default:
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return &BH1750FVI{Bus: bus, i2cAddr: sensorI2cAddr, operationCode: highResOpCode, Poll: pollDelay}
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}
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}
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// NewHighMode returns a BH1750FVI sensor on high resolution mode (1lx resolution)
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func NewHighMode(bus embd.I2CBus) *BH1750FVI {
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return New(High, bus)
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}
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// NewHighMode returns a BH1750FVI sensor on high resolution mode2 (0.5lx resolution)
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func NewHigh2Mode(bus embd.I2CBus) *BH1750FVI {
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return New(High2, bus)
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}
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func (d *BH1750FVI) measureLighting() (float64, error) {
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if err := d.Bus.WriteByte(d.i2cAddr, d.operationCode); err != nil {
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return 0, err
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}
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time.Sleep(180 * time.Millisecond)
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reading, err := d.Bus.ReadWordFromReg(d.i2cAddr, defReadReg)
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if err != nil {
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return 0, err
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}
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return float64(int16(reading)) / measurementAcuuracy, nil
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}
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// Lighting returns the ambient lighting in lx.
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func (d *BH1750FVI) Lighting() (float64, error) {
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select {
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case lighting := <-d.lightingReadings:
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return lighting, nil
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default:
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return d.measureLighting()
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}
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}
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// Run starts continuous sensor data acquisition loop.
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func (d *BH1750FVI) Run() {
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go func() {
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d.quit = make(chan bool)
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timer := time.Tick(time.Duration(d.Poll) * time.Millisecond)
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var lighting float64
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for {
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select {
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case d.lightingReadings <- lighting:
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case <-timer:
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l, err := d.measureLighting()
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if err == nil {
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lighting = l
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}
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if err == nil && d.lightingReadings == nil {
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d.lightingReadings = make(chan float64)
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}
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case <-d.quit:
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d.lightingReadings = nil
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return
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}
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}
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}()
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return
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}
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// Close.
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func (d *BH1750FVI) Close() {
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if d.quit != nil {
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d.quit <- true
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}
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return
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}
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