mirror of https://github.com/kidoman/embd
394 lines
8.0 KiB
Go
394 lines
8.0 KiB
Go
// Package bmp085 allows interfacing with Bosch BMP085 barometric pressure sensor. This sensor
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// has the ability to provided compensated temperature and pressure readings.
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package bmp085
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import (
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"math"
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"sync"
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"time"
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"github.com/golang/glog"
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"github.com/kidoman/embd"
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)
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const (
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address = 0x77
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calAc1 = 0xAA
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calAc2 = 0xAC
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calAc3 = 0xAE
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calAc4 = 0xB0
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calAc5 = 0xB2
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calAc6 = 0xB4
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calB1 = 0xB6
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calB2 = 0xB8
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calMB = 0xBA
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calMC = 0xBC
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calMD = 0xBE
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control = 0xF4
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tempData = 0xF6
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pressureData = 0xF6
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readTempCmd = 0x2E
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readPressureCmd = 0x34
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tempReadDelay = 5 * time.Millisecond
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p0 = 101325
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pollDelay = 250
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)
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// BMP085 represents a Bosch BMP085 barometric sensor.
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type BMP085 struct {
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Bus embd.I2CBus
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Poll int
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oss uint
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ac1, ac2, ac3 int16
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ac4, ac5, ac6 uint16
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b1, b2, mb, mc, md int16
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b5 int32
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calibrated bool
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cmu sync.RWMutex
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temps chan uint16
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pressures chan int32
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altitudes chan float64
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quit chan struct{}
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}
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// New returns a handle to a BMP085 sensor.
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func New(bus embd.I2CBus) *BMP085 {
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return &BMP085{Bus: bus, Poll: pollDelay}
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}
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func (d *BMP085) calibrate() error {
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d.cmu.RLock()
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if d.calibrated {
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d.cmu.RUnlock()
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return nil
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}
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d.cmu.RUnlock()
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d.cmu.Lock()
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defer d.cmu.Unlock()
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readInt16 := func(reg byte) (int16, error) {
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v, err := d.Bus.ReadWordFromReg(address, reg)
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if err != nil {
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return 0, err
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}
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return int16(v), nil
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}
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readUInt16 := func(reg byte) (uint16, error) {
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v, err := d.Bus.ReadWordFromReg(address, reg)
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if err != nil {
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return 0, err
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}
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return uint16(v), nil
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}
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var err error
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d.ac1, err = readInt16(calAc1)
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if err != nil {
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return err
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}
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d.ac2, err = readInt16(calAc2)
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if err != nil {
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return err
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}
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d.ac3, err = readInt16(calAc3)
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if err != nil {
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return err
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}
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d.ac4, err = readUInt16(calAc4)
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if err != nil {
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return err
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}
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d.ac5, err = readUInt16(calAc5)
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if err != nil {
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return err
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}
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d.ac6, err = readUInt16(calAc6)
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if err != nil {
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return err
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}
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d.b1, err = readInt16(calB1)
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if err != nil {
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return err
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}
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d.b2, err = readInt16(calB2)
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if err != nil {
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return err
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}
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d.mb, err = readInt16(calMB)
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if err != nil {
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return err
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}
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d.mc, err = readInt16(calMC)
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if err != nil {
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return err
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}
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d.md, err = readInt16(calMD)
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if err != nil {
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return err
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}
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d.calibrated = true
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if glog.V(1) {
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glog.Info("bmp085: calibration data retrieved")
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glog.Infof("bmp085: param AC1 = %v", d.ac1)
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glog.Infof("bmp085: param AC2 = %v", d.ac2)
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glog.Infof("bmp085: param AC3 = %v", d.ac3)
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glog.Infof("bmp085: param AC4 = %v", d.ac4)
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glog.Infof("bmp085: param AC5 = %v", d.ac5)
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glog.Infof("bmp085: param AC6 = %v", d.ac6)
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glog.Infof("bmp085: param B1 = %v", d.b1)
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glog.Infof("bmp085: param B2 = %v", d.b2)
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glog.Infof("bmp085: param MB = %v", d.mb)
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glog.Infof("bmp085: param MC = %v", d.mc)
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glog.Infof("bmp085: param MD = %v", d.md)
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}
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return nil
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}
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func (d *BMP085) readUncompensatedTemp() (uint16, error) {
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if err := d.Bus.WriteByteToReg(address, control, readTempCmd); err != nil {
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return 0, err
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}
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time.Sleep(tempReadDelay)
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temp, err := d.Bus.ReadWordFromReg(address, tempData)
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if err != nil {
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return 0, err
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}
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return temp, nil
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}
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func (d *BMP085) calcTemp(utemp uint16) uint16 {
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x1 := ((int(utemp) - int(d.ac6)) * int(d.ac5)) >> 15
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x2 := (int(d.mc) << 11) / (x1 + int(d.md))
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d.cmu.Lock()
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d.b5 = int32(x1 + x2)
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d.cmu.Unlock()
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return uint16((d.b5 + 8) >> 4)
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}
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func (d *BMP085) measureTemp() (uint16, error) {
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if err := d.calibrate(); err != nil {
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return 0, err
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}
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utemp, err := d.readUncompensatedTemp()
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if err != nil {
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return 0, err
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}
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glog.V(1).Infof("bcm085: uncompensated temp: %v", utemp)
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temp := d.calcTemp(utemp)
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glog.V(1).Infof("bcm085: compensated temp %v", temp)
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return temp, nil
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}
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// Temperature returns the current temperature reading.
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func (d *BMP085) Temperature() (float64, error) {
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select {
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case t := <-d.temps:
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temp := float64(t) / 10
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return temp, nil
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default:
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glog.V(1).Infof("bcm085: no temps available... measuring")
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t, err := d.measureTemp()
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if err != nil {
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return 0, err
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}
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temp := float64(t) / 10
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return temp, nil
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}
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}
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func (d *BMP085) readUncompensatedPressure() (uint32, error) {
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if err := d.Bus.WriteByteToReg(address, control, byte(readPressureCmd+(d.oss<<6))); err != nil {
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return 0, err
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}
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time.Sleep(time.Duration(2+(3<<d.oss)) * time.Millisecond)
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data := make([]byte, 3)
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if err := d.Bus.ReadFromReg(address, pressureData, data); err != nil {
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return 0, err
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}
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pressure := ((uint32(data[0]) << 16) | (uint32(data[1]) << 8) | uint32(data[2])) >> (8 - d.oss)
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return pressure, nil
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}
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func (d *BMP085) calcPressure(upressure uint32) int32 {
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var x1, x2, x3 int32
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l := func(s string, v interface{}) {
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glog.V(1).Infof("bcm085: %v = %v", s, v)
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}
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b6 := d.b5 - 4000
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l("b6", b6)
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// Calculate b3
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x1 = (int32(d.b2) * int32(b6*b6) >> 12) >> 11
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x2 = (int32(d.ac2) * b6) >> 11
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x3 = x1 + x2
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b3 := (((int32(d.ac1)*4 + x3) << d.oss) + 2) >> 2
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l("x1", x1)
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l("x2", x2)
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l("x3", x3)
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l("b3", b3)
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// Calculate b4
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x1 = (int32(d.ac3) * b6) >> 13
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x2 = (int32(d.b1) * ((b6 * b6) >> 12)) >> 16
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x3 = ((x1 + x2) + 2) >> 2
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b4 := (uint32(d.ac4) * uint32(x3+32768)) >> 15
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l("x1", x1)
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l("x2", x2)
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l("x3", x3)
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l("b4", b4)
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var p int32
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b7 := (uint32(upressure-uint32(b3)) * (50000 >> d.oss))
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if b7 < 0x80000000 {
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p = int32((b7 << 1) / b4)
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} else {
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p = int32((b7 / b4) << 1)
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}
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l("b7", b7)
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l("p", p)
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x1 = (p >> 8) * (p >> 8)
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x1 = (x1 * 3038) >> 16
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x2 = (-7357 * p) >> 16
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p += (x1 + x2 + 3791) >> 4
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l("x1", x1)
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l("x2", x2)
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l("x3", x3)
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l("p", p)
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return p
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}
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func (d *BMP085) calcAltitude(pressure int32) float64 {
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return 44330 * (1 - math.Pow(float64(pressure)/p0, 0.190295))
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}
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func (d *BMP085) measurePressureAndAltitude() (int32, float64, error) {
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if err := d.calibrate(); err != nil {
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return 0, 0, err
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}
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upressure, err := d.readUncompensatedPressure()
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if err != nil {
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return 0, 0, err
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}
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glog.V(1).Infof("bcm085: uncompensated pressure: %v", upressure)
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pressure := d.calcPressure(upressure)
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glog.V(1).Infof("bcm085: compensated pressure %v", pressure)
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altitude := d.calcAltitude(pressure)
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glog.V(1).Infof("bcm085: calculated altitude %v", altitude)
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return pressure, altitude, nil
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}
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// Pressure returns the current pressure reading.
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func (d *BMP085) Pressure() (int, error) {
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if err := d.calibrate(); err != nil {
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return 0, err
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}
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select {
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case p := <-d.pressures:
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return int(p), nil
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default:
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glog.V(1).Infof("bcm085: no pressures available... measuring")
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p, _, err := d.measurePressureAndAltitude()
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if err != nil {
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return 0, err
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}
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return int(p), nil
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}
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}
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// Altitude returns the current altitude reading.
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func (d *BMP085) Altitude() (float64, error) {
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if err := d.calibrate(); err != nil {
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return 0, err
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}
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select {
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case altitude := <-d.altitudes:
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return altitude, nil
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default:
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glog.V(1).Info("bcm085: no altitudes available... measuring")
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_, altitude, err := d.measurePressureAndAltitude()
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if err != nil {
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return 0, err
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}
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return altitude, nil
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}
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}
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// Run starts the sensor data acquisition loop.
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func (d *BMP085) Run() {
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go func() {
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d.quit = make(chan struct{})
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timer := time.Tick(time.Duration(d.Poll) * time.Millisecond)
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var temp uint16
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var pressure int32
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var altitude float64
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for {
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select {
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case <-timer:
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t, err := d.measureTemp()
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if err == nil {
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temp = t
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}
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if err == nil && d.temps == nil {
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d.temps = make(chan uint16)
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}
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p, a, err := d.measurePressureAndAltitude()
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if err == nil {
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pressure = p
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altitude = a
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}
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if err == nil && d.pressures == nil && d.altitudes == nil {
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d.pressures = make(chan int32)
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d.altitudes = make(chan float64)
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}
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case d.temps <- temp:
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case d.pressures <- pressure:
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case d.altitudes <- altitude:
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case <-d.quit:
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d.temps = nil
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d.pressures = nil
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d.altitudes = 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 *BMP085) Close() {
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if d.quit != nil {
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d.quit <- struct{}{}
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}
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}
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