support for MCP4725 DAC

README.md

@@ -65,7 +65,13 @@ Use various sensors on the RaspberryPi with Golang (like a ninja!)
 ## Controllers
 
 ### PCA9685
+
   16-channel, 12-bit PWM Controller with I2C protocol
 
-  [Datasheet] (http://www.adafruit.com/datasheets/PCA9685.pdf)
+  [Documentation](http://godoc.org/github.com/kid0m4n/go-rpi/controller/pca9685) [Datasheet](http://www.adafruit.com/datasheets/PCA9685.pdf) [Product Page](http://www.adafruit.com/products/815)
-  [Product Page] (http://www.adafruit.com/products/815)
+
+### MCP4725
+
+  12-bit DAC
+
+  [Documentation](http://godoc.org/github.com/kid0m4n/go-rpi/controller/mcp4725) [Datasheet](http://www.adafruit.com/datasheets/mcp4725.pdf) [Product Page](http://www.adafruit.com/products/935)

controller/mcp4725/mcp4725.go

@@ -0,0 +1,105 @@
+// Package mcp4725 allows interfacing with the MCP4725 DAC.
+package mcp4725
+
+import (
+	"log"
+	"sync"
+
+	"github.com/kid0m4n/go-rpi/i2c"
+)
+
+const (
+	dacReg     = 0x40
+	programReg = 0x60
+	powerDown  = 0x46
+
+	genReset = 0x06
+	powerUp  = 0x09
+)
+
+// MCP4725 represents a MCP4725 DAC.
+type MCP4725 struct {
+	// Bus to communicate over.
+	Bus i2c.Bus
+	// Addr of the sensor.
+	Addr byte
+
+	initialized bool
+	mu          sync.RWMutex
+
+	// Debug turns on additional debug output.
+	Debug bool
+}
+
+// New creates a new MCP4725 sensor.
+func New(bus i2c.Bus, addr byte) *MCP4725 {
+	return &MCP4725{
+		Bus:  bus,
+		Addr: addr,
+	}
+}
+
+func (d *MCP4725) setup() (err error) {
+	d.mu.RLock()
+	if d.initialized {
+		d.mu.RUnlock()
+		return
+	}
+	d.mu.RUnlock()
+
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	if d.Debug {
+		log.Print("mcp4725: general call reset")
+	}
+	if err = d.Bus.WriteByteToReg(d.Addr, 0x00, powerUp); err != nil {
+		return
+	}
+	if err = d.Bus.WriteByteToReg(d.Addr, 0x00, genReset); err != nil {
+		return
+	}
+	d.initialized = true
+	return
+}
+
+func (d *MCP4725) setVoltage(voltage int, reg byte) (err error) {
+	if err = d.setup(); err != nil {
+		return
+	}
+	if voltage > 4095 {
+		voltage = 4095
+	}
+	if voltage < 0 {
+		voltage = 0
+	}
+	if d.Debug {
+		log.Printf("mcp4725: setting voltage to %04d", voltage)
+	}
+	if err = d.Bus.WriteWordToReg(d.Addr, reg, uint16(voltage<<4)); err != nil {
+		return
+	}
+	return
+}
+
+// SetVoltage sets the output voltage.
+func (d *MCP4725) SetVoltage(voltage int) (err error) {
+	return d.setVoltage(voltage, dacReg)
+}
+
+// SetPersistedVoltage sets the voltage and programs the EEPROM so
+// that the voltage is restored on reboot.
+func (d *MCP4725) SetPersistedVoltage(voltage int) (err error) {
+	return d.setVoltage(voltage, programReg)
+}
+
+// Close puts the DAC into power down mode.
+func (d *MCP4725) Close() (err error) {
+	if d.Debug {
+		log.Print("mcp4725: powering down")
+	}
+	if err = d.Bus.WriteWordToReg(d.Addr, powerDown, 0); err != nil {
+		return
+	}
+	return
+}

samples/mcp4725.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"log"
+	"math/rand"
+	"os"
+	"os/signal"
+
+	"github.com/kid0m4n/go-rpi/controller/mcp4725"
+	"github.com/kid0m4n/go-rpi/i2c"
+)
+
+func main() {
+	bus, err := i2c.NewBus(1)
+	if err != nil {
+		log.Panic(err)
+	}
+
+	dac := mcp4725.New(bus, 0x62)
+	defer dac.Close()
+
+	stop := make(chan os.Signal, 1)
+	signal.Notify(stop, os.Interrupt, os.Kill)
+
+	for {
+		select {
+		case <-stop:
+			return
+		default:
+			voltage := rand.Intn(4096)
+			if err := dac.SetVoltage(voltage); err != nil {
+				log.Printf("mcp4725: %v", err)
+			}
+		}
+	}
+}