support for MCP4725 DAC

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
+}