support for bmp180

README.md

@@ -20,6 +20,12 @@ Use various sensors on the RaspberryPi with Golang (like a ninja!)
 
   [Documentation](http://godoc.org/github.com/kid0m4n/go-rpi/sensor/bmp085) [Datasheet](https://www.sparkfun.com/datasheets/Components/General/BST-BMP085-DS000-05.pdf)
 
+### BMP180
+
+  Barometric pressure sensor
+
+  [Documentation](http://godoc.org/github.com/kid0m4n/go-rpi/sensor/bmp180) [Datasheet](http://www.adafruit.com/datasheets/BST-BMP180-DS000-09.pdf)
+
 ### LSM303
 
   Accelerometer and magnetometer

samples/bmp180.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"log"
+	"time"
+
+	"github.com/kid0m4n/go-rpi/i2c"
+	"github.com/kid0m4n/go-rpi/sensor/bmp180"
+)
+
+func main() {
+	bus, err := i2c.NewBus(1)
+	if err != nil {
+		log.Panic(err)
+	}
+	baro := bmp180.New(bus)
+	defer baro.Close()
+
+	for {
+		temp, err := baro.Temperature()
+		if err != nil {
+			log.Panic(err)
+		}
+		log.Printf("Temp is %v", temp)
+		pressure, err := baro.Pressure()
+		if err != nil {
+			log.Panic(err)
+		}
+		log.Printf("Pressure is %v", pressure)
+		altitude, err := baro.Altitude()
+		if err != nil {
+			log.Panic(err)
+		}
+		log.Printf("Altitude is %v", altitude)
+
+		time.Sleep(500 * time.Millisecond)
+	}
+}

sensor/bmp180/bmp180.go

@@ -0,0 +1,475 @@
+// Package bmp180 allows interfacing with Bosch BMP180 barometric pressure sensor. This sensor
+// has the ability to provided compensated temperature and pressure readings.
+package bmp180
+
+import (
+	"log"
+	"math"
+	"sync"
+	"time"
+
+	"github.com/kid0m4n/go-rpi/i2c"
+)
+
+const (
+	address = 0x77
+
+	calAc1          = 0xAA
+	calAc2          = 0xAC
+	calAc3          = 0xAE
+	calAc4          = 0xB0
+	calAc5          = 0xB2
+	calAc6          = 0xB4
+	calB1           = 0xB6
+	calB2           = 0xB8
+	calMB           = 0xBA
+	calMC           = 0xBC
+	calMD           = 0xBE
+	control         = 0xF4
+	tempData        = 0xF6
+	pressureData    = 0xF6
+	readTempCmd     = 0x2E
+	readPressureCmd = 0x34
+
+	tempReadDelay = 5 * time.Millisecond
+
+	p0 = 101325
+
+	pollDelay = 250
+)
+
+// A BMP180 implements access to the Bosch BMP180 sensor.
+type BMP180 interface {
+	// SetPollDelay sets the delay between runs of the data acquisition loop.
+	SetPollDelay(delay int)
+
+	// Temperature returns the current temperature reading.
+	Temperature() (temp float64, err error)
+	// Pressure returns the current pressure reading.
+	Pressure() (pressure int, err error)
+	// Altitude returns the current altitude reading.
+	Altitude() (altitude float64, err error)
+
+	// Run starts the sensor data acquisition loop.
+	Run() error
+	// Close.
+	Close()
+}
+
+type bmp180 struct {
+	bus i2c.Bus
+	oss uint
+
+	ac1, ac2, ac3      int16
+	ac4, ac5, ac6      uint16
+	b1, b2, mb, mc, md int16
+	b5                 int32
+	calibrated         bool
+	cmu                *sync.RWMutex
+
+	poll      int
+	temps     chan uint16
+	pressures chan int32
+	altitudes chan float64
+	quit      chan struct{}
+
+	debug bool
+}
+
+// Default instance of the BMP180 sensor.
+var Default = New(i2c.Default)
+
+// New creates a new BMP180 interface. The bus variable controls
+// the I2C bus used to communicate with the device.
+func New(bus i2c.Bus) BMP180 {
+	return &bmp180{bus: bus, cmu: new(sync.RWMutex), poll: pollDelay}
+}
+
+// SetPollDelay sets the delay between runs of the data acquisition loop.
+func (d *bmp180) SetPollDelay(delay int) {
+	d.poll = delay
+}
+
+func (d *bmp180) calibrate() (err error) {
+	d.cmu.RLock()
+	if d.calibrated {
+		d.cmu.RUnlock()
+		return
+	}
+	d.cmu.RUnlock()
+
+	d.cmu.Lock()
+	defer d.cmu.Unlock()
+
+	readInt16 := func(reg byte) (value int16, err error) {
+		var v int
+		if v, err = d.bus.ReadInt(address, reg); err != nil {
+			return
+		}
+		value = int16(v)
+		return
+	}
+
+	readUInt16 := func(reg byte) (value uint16, err error) {
+		var v int
+		if v, err = d.bus.ReadInt(address, reg); err != nil {
+			return
+		}
+		value = uint16(v)
+		return
+	}
+
+	d.ac1, err = readInt16(calAc1)
+	if err != nil {
+		return
+	}
+	d.ac2, err = readInt16(calAc2)
+	if err != nil {
+		return
+	}
+	d.ac3, err = readInt16(calAc3)
+	if err != nil {
+		return
+	}
+	d.ac4, err = readUInt16(calAc4)
+	if err != nil {
+		return
+	}
+	d.ac5, err = readUInt16(calAc5)
+	if err != nil {
+		return
+	}
+	d.ac6, err = readUInt16(calAc6)
+	if err != nil {
+		return
+	}
+	d.b1, err = readInt16(calB1)
+	if err != nil {
+		return
+	}
+	d.b2, err = readInt16(calB2)
+	if err != nil {
+		return
+	}
+	d.mb, err = readInt16(calMB)
+	if err != nil {
+		return
+	}
+	d.mc, err = readInt16(calMC)
+	if err != nil {
+		return
+	}
+	d.md, err = readInt16(calMD)
+	if err != nil {
+		return
+	}
+
+	d.calibrated = true
+
+	if d.debug {
+		log.Print("bmp180: calibration data retrieved")
+		log.Printf("bmp180: param AC1 = %v", d.ac1)
+		log.Printf("bmp180: param AC2 = %v", d.ac2)
+		log.Printf("bmp180: param AC3 = %v", d.ac3)
+		log.Printf("bmp180: param AC4 = %v", d.ac4)
+		log.Printf("bmp180: param AC5 = %v", d.ac5)
+		log.Printf("bmp180: param AC6 = %v", d.ac6)
+		log.Printf("bmp180: param B1 = %v", d.b1)
+		log.Printf("bmp180: param B2 = %v", d.b2)
+		log.Printf("bmp180: param MB = %v", d.mb)
+		log.Printf("bmp180: param MC = %v", d.mc)
+		log.Printf("bmp180: param MD = %v", d.md)
+	}
+
+	return
+}
+
+func (d *bmp180) readUncompensatedTemp() (temp uint16, err error) {
+	if err = d.bus.WriteToReg(address, control, readTempCmd); err != nil {
+		return
+	}
+	time.Sleep(tempReadDelay)
+	var t int
+	t, err = d.bus.ReadInt(address, tempData)
+	if err != nil {
+		return
+	}
+	temp = uint16(t)
+	return
+}
+
+func (d *bmp180) calcTemp(utemp uint16) uint16 {
+	x1 := ((int(utemp) - int(d.ac6)) * int(d.ac5)) >> 15
+	x2 := (int(d.mc) << 11) / (x1 + int(d.md))
+
+	d.cmu.Lock()
+	d.b5 = int32(x1 + x2)
+	d.cmu.Unlock()
+
+	return uint16((d.b5 + 8) >> 4)
+}
+
+func (d *bmp180) measureTemp() (temp uint16, err error) {
+	if err = d.calibrate(); err != nil {
+		return
+	}
+
+	var utemp uint16
+	if utemp, err = d.readUncompensatedTemp(); err != nil {
+		return
+	}
+	if d.debug {
+		log.Printf("bcm180: uncompensated temp: %v", utemp)
+	}
+	temp = d.calcTemp(utemp)
+	if d.debug {
+		log.Printf("bcm180: compensated temp %v", temp)
+	}
+	return
+}
+
+// Temperature returns the current temperature reading.
+func (d *bmp180) Temperature() (temp float64, err error) {
+
+	select {
+	case t := <-d.temps:
+		temp = float64(t) / 10
+		return
+	default:
+		if d.debug {
+			log.Print("bcm180: no temps available... measuring")
+		}
+		var t uint16
+		t, err = d.measureTemp()
+		if err != nil {
+			return
+		}
+		temp = float64(t) / 10
+		return
+	}
+}
+
+func (d *bmp180) readUncompensatedPressure() (pressure uint32, err error) {
+	if err = d.bus.WriteToReg(address, control, byte(readPressureCmd+(d.oss<<6))); err != nil {
+		return
+	}
+	time.Sleep(time.Duration(2+(3<<d.oss)) * time.Millisecond)
+
+	data := make([]byte, 3)
+	if err = d.bus.ReadFromReg(address, pressureData, data); err != nil {
+		return
+	}
+
+	pressure = ((uint32(data[0]) << 16) | (uint32(data[1]) << 8) | uint32(data[2])) >> (8 - d.oss)
+
+	return
+}
+
+func (d *bmp180) calcPressure(upressure uint32) (p int32) {
+	var x1, x2, x3 int32
+
+	l := func(s string, v interface{}) {
+		if d.debug {
+			log.Printf("bcm180: %v = %v", s, v)
+		}
+	}
+
+	b6 := d.b5 - 4000
+	l("b6", b6)
+
+	// Calculate b3
+	x1 = (int32(d.b2) * int32(b6*b6) >> 12) >> 11
+	x2 = (int32(d.ac2) * b6) >> 11
+	x3 = x1 + x2
+	b3 := (((int32(d.ac1)*4 + x3) << d.oss) + 2) >> 2
+
+	l("x1", x1)
+	l("x2", x2)
+	l("x3", x3)
+	l("b3", b3)
+
+	// Calculate b4
+	x1 = (int32(d.ac3) * b6) >> 13
+	x2 = (int32(d.b1) * ((b6 * b6) >> 12)) >> 16
+	x3 = ((x1 + x2) + 2) >> 2
+	b4 := (uint32(d.ac4) * uint32(x3+32768)) >> 15
+
+	l("x1", x1)
+	l("x2", x2)
+	l("x3", x3)
+	l("b4", b4)
+
+	b7 := (uint32(upressure-uint32(b3)) * (50000 >> d.oss))
+	if b7 < 0x80000000 {
+		p = int32((b7 << 1) / b4)
+	} else {
+		p = int32((b7 / b4) << 1)
+	}
+	l("b7", b7)
+	l("p", p)
+
+	x1 = (p >> 8) * (p >> 8)
+	x1 = (x1 * 3038) >> 16
+	x2 = (-7357 * p) >> 16
+	p += (x1 + x2 + 3791) >> 4
+
+	l("x1", x1)
+	l("x2", x2)
+	l("x3", x3)
+	l("p", p)
+
+	return
+}
+
+func (d *bmp180) calcAltitude(pressure int32) float64 {
+	return 44330 * (1 - math.Pow(float64(pressure)/p0, 0.190295))
+}
+
+func (d *bmp180) measurePressureAndAltitude() (pressure int32, altitude float64, err error) {
+	if err = d.calibrate(); err != nil {
+		return
+	}
+
+	var upressure uint32
+	if upressure, err = d.readUncompensatedPressure(); err != nil {
+		return
+	}
+	if d.debug {
+		log.Printf("bcm180: uncompensated pressure: %v", upressure)
+	}
+	pressure = d.calcPressure(upressure)
+	if d.debug {
+		log.Printf("bcm180: compensated pressure %v", pressure)
+	}
+	altitude = d.calcAltitude(pressure)
+	if d.debug {
+		log.Printf("bcm180: calculated altitude %v", altitude)
+	}
+	return
+}
+
+// Pressure returns the current pressure reading.
+func (d *bmp180) Pressure() (pressure int, err error) {
+	if err = d.calibrate(); err != nil {
+		return
+	}
+
+	select {
+	case p := <-d.pressures:
+		pressure = int(p)
+		return
+	default:
+		if d.debug {
+			log.Print("bcm180: no pressures available... measuring")
+		}
+		var p int32
+		p, _, err = d.measurePressureAndAltitude()
+		if err != nil {
+			return
+		}
+		pressure = int(p)
+		return
+	}
+}
+
+// Altitude returns the current altitude reading.
+func (d *bmp180) Altitude() (altitude float64, err error) {
+	if err = d.calibrate(); err != nil {
+		return
+	}
+
+	select {
+	case altitude = <-d.altitudes:
+		return
+	default:
+		if d.debug {
+			log.Print("bcm180: no altitudes available... measuring")
+		}
+		_, altitude, err = d.measurePressureAndAltitude()
+		if err != nil {
+			return
+		}
+		return
+	}
+}
+
+// Run starts the sensor data acquisition loop.
+func (d *bmp180) Run() (err error) {
+	go func() {
+		d.quit = make(chan struct{})
+		timer := time.Tick(time.Duration(d.poll) * time.Millisecond)
+
+		var temp uint16
+		var pressure int32
+		var altitude float64
+
+		for {
+			select {
+			case <-timer:
+				t, err := d.measureTemp()
+				if err == nil {
+					temp = t
+				}
+				if err == nil && d.temps == nil {
+					d.temps = make(chan uint16)
+				}
+				p, a, err := d.measurePressureAndAltitude()
+				if err == nil {
+					pressure = p
+					altitude = a
+				}
+				if err == nil && d.pressures == nil && d.altitudes == nil {
+					d.pressures = make(chan int32)
+					d.altitudes = make(chan float64)
+				}
+			case d.temps <- temp:
+			case d.pressures <- pressure:
+			case d.altitudes <- altitude:
+			case <-d.quit:
+				d.temps = nil
+				d.pressures = nil
+				d.altitudes = nil
+				return
+			}
+		}
+	}()
+
+	return
+}
+
+// Close.
+func (d *bmp180) Close() {
+	if d.quit != nil {
+		d.quit <- struct{}{}
+	}
+}
+
+// SetPollDelay sets the delay between runs of the data acquisition loop.
+func SetPollDelay(delay int) {
+	Default.SetPollDelay(delay)
+}
+
+// Temperature returns the current temperature reading.
+func Temperature() (temp float64, err error) {
+	return Default.Temperature()
+}
+
+// Pressure returns the current pressure reading.
+func Pressure() (pressure int, err error) {
+	return Default.Pressure()
+}
+
+// Altitude returns the current altitude reading.
+func Altitude() (altitude float64, err error) {
+	return Default.Altitude()
+}
+
+// Run starts the sensor data acquisition loop.
+func Run() (err error) {
+	return Default.Run()
+}
+
+// Close.
+func Close() {
+	Default.Close()
+}