From 2ac61dad95f0a876e724671afefc5f07a6da4e54 Mon Sep 17 00:00:00 2001
From: Kunal Powar <kunalpowar1203@gmail.com>
Date: Tue, 17 Dec 2013 20:37:58 +0530
Subject: [PATCH] Added Package and sample for bh1750Fvi

---
 samples/bh1750Fvi.go          |  29 ++++++
 sensor/bh1750Fvi/bh1750Fvi.go | 175 ++++++++++++++++++++++++++++++++++
 2 files changed, 204 insertions(+)
 create mode 100644 samples/bh1750Fvi.go
 create mode 100644 sensor/bh1750Fvi/bh1750Fvi.go

diff --git a/samples/bh1750Fvi.go b/samples/bh1750Fvi.go
new file mode 100644
index 0000000..b4badf6
--- /dev/null
+++ b/samples/bh1750Fvi.go
@@ -0,0 +1,29 @@
+package main
+
+import (
+	"log"
+	"time"
+
+	"github.com/kid0m4n/go-rpi/i2c"
+	"github.com/kid0m4n/go-rpi/sensor/bh1750Fvi"
+)
+
+func main() {
+	bus, err := i2c.NewBus(1)
+	if err != nil {
+		log.Panic(err)
+	}
+
+	lightingSensor := bh1750Fvi.New("H", bus)
+
+	defer lightingSensor.Close()
+
+	for {
+		lighting, err := lightingSensor.Lighting()
+		if err != nil {
+			log.Panic(err)
+		}
+		log.Printf("Lighting is %v", lighting, "lx")
+		time.Sleep(500 * time.Millisecond)
+	}
+}
diff --git a/sensor/bh1750Fvi/bh1750Fvi.go b/sensor/bh1750Fvi/bh1750Fvi.go
new file mode 100644
index 0000000..a2ba548
--- /dev/null
+++ b/sensor/bh1750Fvi/bh1750Fvi.go
@@ -0,0 +1,175 @@
+// Package BH1750FVI allows interfacing with the BH1750FVI ambient light sensor through I2C protocol
+package bh1750Fvi
+
+import (
+	"log"
+	"sync"
+	"time"
+
+	"github.com/kid0m4n/go-rpi/i2c"
+)
+
+const (
+	measurementAcuuracy = 1.2 // [accuracy = sensorValue/actualValue] (min = 0.96, typ = 1.2, max = 1.44)
+
+	highResolutionReadAddress   = 0x23
+	highResolutionOperationCode = 0x10
+
+	lowResolutionReadAddress   = 0x5c
+	lowResolutionOperationCode = 0x23
+
+	highResolutionMode2ReadAddress   = 0x23
+	highResolutionMode2OperationCode = 0x11
+
+	pollDelay = 150
+)
+
+type BH1750VI interface {
+	Start() error
+
+	Lighting() (lighting float64, err error)
+
+	Close()
+
+	SetPollDelay(delay int)
+}
+
+type bh1750vi struct {
+	bus i2c.Bus
+	mu  *sync.RWMutex
+
+	lightingReadings chan float64
+	quit             chan bool
+
+	ready bool
+
+	readRegisterAddress byte
+	operationCode       byte
+
+	continuousMode bool
+
+	poll int
+}
+
+var Default = New("H", i2c.Default)
+
+func New(mode string, bus i2c.Bus) BH1750VI {
+
+	/*
+		Supports three modes:
+		"L" -> Low resolution mode (4lx), takes 16ms
+		"H" -> High resolution mode (1lx), takes 120ms (recommended)
+		"H2" -> High resolution mode 2 (0.5lx), takes 120ms (only use for low light)
+	*/
+
+	switch mode {
+	case "L":
+		return &bh1750vi{bus: bus, readRegisterAddress: lowResolutionReadAddress, operationCode: lowResolutionOperationCode, continuousMode: false}
+	case "H":
+		return &bh1750vi{bus: bus, readRegisterAddress: highResolutionReadAddress, operationCode: highResolutionOperationCode, continuousMode: true}
+	case "H2":
+		return &bh1750vi{bus: bus, readRegisterAddress: highResolutionMode2ReadAddress, operationCode: highResolutionMode2OperationCode, continuousMode: true}
+	default:
+		return &bh1750vi{bus: bus, readRegisterAddress: highResolutionReadAddress, operationCode: highResolutionOperationCode, continuousMode: true}
+	}
+}
+
+func (sensor *bh1750vi) setup() (err error) {
+	sensor.mu.Lock()
+
+	if sensor.ready && sensor.continuousMode { //for Low resolution mode sensor has to be initialized for every read.
+		sensor.mu.Unlock()
+		return
+	}
+
+	defer sensor.mu.Unlock()
+
+	err = sensor.bus.WriteByte(sensor.readRegisterAddress, sensor.operationCode)
+	if err != nil {
+		log.Print("bh1750vi: Failed to initialize sensor")
+		return
+	}
+
+	sensor.ready = true
+	return
+}
+
+func (sensor *bh1750vi) measureLighting() (lighting float64, err error) {
+	if err = sensor.setup(); err != nil {
+		return
+	}
+
+	sensorData := make([]byte, 2)
+	if err = sensor.bus.ReadFromReg(sensor.readRegisterAddress, sensor.operationCode, sensorData); err != nil {
+		return
+	}
+
+	sensorReading := (int16(sensorData[0] << 8)) | (int16(sensorData[1]))
+	lighting = float64(sensorReading) / measurementAcuuracy
+
+	return
+}
+
+func (sensor *bh1750vi) Lighting() (lighting float64, err error) {
+	select {
+	case lighting = <-sensor.lightingReadings:
+		return
+	default:
+		return sensor.measureLighting()
+
+	}
+}
+
+func (sensor *bh1750vi) Start() (err error) {
+	go func() {
+		sensor.quit = make(chan bool)
+
+		timer := time.Tick(time.Duration(sensor.poll) * time.Millisecond)
+
+		var lighting float64
+
+		for {
+			select {
+			case sensor.lightingReadings <- lighting:
+			case <-timer:
+				if l, err := sensor.measureLighting(); err == nil {
+					lighting = l
+				}
+				if err == nil && sensor.lightingReadings == nil {
+					sensor.lightingReadings = make(chan float64)
+				}
+			case <-sensor.quit:
+				sensor.lightingReadings = nil
+				return
+			}
+		}
+	}()
+	return
+}
+
+func (sensor *bh1750vi) Close() {
+	if sensor.quit != nil {
+		sensor.quit <- true
+	}
+	return
+}
+
+func (sensor *bh1750vi) SetPollDelay(delay int) {
+	sensor.poll = delay
+}
+
+func SetPollDelay(delay int) {
+	Default.SetPollDelay(delay)
+}
+
+func Lighting() (lighting float64, err error) {
+	return Default.Lighting()
+}
+
+func Start() (err error) {
+	return Default.Start()
+}
+
+func Close() {
+	Default.Close()
+}