Add I2C INA219 driver (#705)

INA219: add INA219 driver

ina219/config.go

@@ -0,0 +1,183 @@
+package ina219
+
+type Config struct {
+	// BusVoltageRange sets the bus voltage range.
+	BusVoltageRange BusVoltageRange
+
+	// PGA sets the programmable gain amplifier.
+	PGA PGA
+
+	// BusADC sets the bus ADC resolution.
+	BusADC BusADC
+
+	// ShuntADC sets the shunt ADC resolution.
+	ShuntADC ShuntADC
+
+	// Mode sets the operating mode.
+	Mode Mode
+
+	// Calibration sets the calibration value for the expected
+	// voltage and current values.
+	Calibration Calibration
+
+	// 1000 / uA per bit
+	CurrentDivider float32
+
+	// 1mW per bit
+	PowerMultiplier float32
+}
+
+// RegisterValue returns the register value of the configuration.
+func (c *Config) RegisterValue() uint16 {
+	return c.BusVoltageRange.RegisterValue() |
+		c.PGA.RegisterValue() |
+		c.BusADC.RegisterValue() |
+		c.ShuntADC.RegisterValue() |
+		c.Mode.RegisterValue()
+}
+
+// Generate a new configuration from a register value.
+func NewConfig(config int16, calibration int16) Config {
+	return Config{
+		BusVoltageRange: BusVoltageRange(config >> 13 & 0x1),
+		PGA:             PGA(config >> 11 & 0x3),
+		BusADC:          BusADC(config >> 7 & 0xF),
+		ShuntADC:        ShuntADC(config >> 3 & 0xF),
+		Mode:            Mode(config & 0x7),
+		Calibration:     Calibration(calibration),
+	}
+}
+
+// Configurations from
+// https://github.com/adafruit/Adafruit_INA219/blob/master/Adafruit_INA219.cpp
+var (
+	// Config32V2A is a configuration for a 32V 2A range.
+	Config32V2A = Config{
+		BusVoltageRange: Range32V,
+		PGA:             PGA8,
+		BusADC:          ADC12,
+		ShuntADC:        SADC12,
+		Mode:            ModeContShuntBus,
+		Calibration:     Calibration16V400mA,
+		CurrentDivider:  10.0,
+		PowerMultiplier: 2.0,
+	}
+
+	// Config32V1A is a configuration for a 32V 1A range.
+	Config32V1A = Config{
+		BusVoltageRange: Range32V,
+		PGA:             PGA8,
+		BusADC:          ADC12,
+		ShuntADC:        SADC12,
+		Mode:            ModeContShuntBus,
+		Calibration:     Calibration32V1A,
+		CurrentDivider:  25.0,
+		PowerMultiplier: 0.8,
+	}
+
+	// Config16V400mA is a configuration for a 16V 400mA range.
+	Config16V400mA = Config{
+		BusVoltageRange: Range16V,
+		PGA:             PGA1,
+		BusADC:          ADC12,
+		ShuntADC:        SADC12,
+		Mode:            ModeContShuntBus,
+		Calibration:     Calibration16V400mA,
+		CurrentDivider:  20.0,
+		PowerMultiplier: 1.0,
+	}
+)
+
+// BusVoltageRange is the bus voltage range.
+type BusVoltageRange int8
+
+const (
+	Range16V BusVoltageRange = 0 // 0-16V
+	Range32V BusVoltageRange = 1 // 0-32V
+)
+
+func (r BusVoltageRange) RegisterValue() uint16 {
+	return uint16(r) << 13
+}
+
+// PGA is the programmable gain amplifier.
+type PGA int8
+
+const (
+	PGA1 PGA = 0 // 40mV
+	PGA2 PGA = 1 // 80mV
+	PGA4 PGA = 2 // 160mV
+	PGA8 PGA = 3 // 320mV
+)
+
+func (p PGA) RegisterValue() uint16 {
+	return uint16(p) << 11
+}
+
+// BusADC is the bus ADC resolution.
+type BusADC int8
+
+const (
+	ADC9  BusADC = 0 // 9-bit
+	ADC10 BusADC = 1 // 10-bit
+	ADC11 BusADC = 2 // 11-bit
+	ADC12 BusADC = 3 // 12-bit
+)
+
+func (b BusADC) RegisterValue() uint16 {
+	return uint16(b) << 7
+}
+
+// ShuntADC is the shunt ADC resolution.
+type ShuntADC int8
+
+const (
+	SADC9  ShuntADC = 0 // 9-bit
+	SADC10 ShuntADC = 1 // 10-bit
+	SADC11 ShuntADC = 2 // 11-bit
+	SADC12 ShuntADC = 3 // 12-bit
+)
+
+func (s ShuntADC) RegisterValue() uint16 {
+	return uint16(s) << 3
+}
+
+// Mode is the operating mode.
+type Mode int8
+
+const (
+	ModePowerDown    Mode = 0 // power-down
+	ModeTrigShunt    Mode = 1 // triggered shunt voltage
+	ModeTrigBus      Mode = 2 // triggered bus voltage
+	ModeTrigShuntBus Mode = 3 // triggered shunt and bus voltage
+	ModeADCOff       Mode = 4 // ADC off
+	ModeContShunt    Mode = 5 // continuous shunt voltage
+	ModeContBus      Mode = 6 // continuous bus voltage
+	ModeContShuntBus Mode = 7 // continuous shunt and bus voltage
+)
+
+// ModeTriggered is a mask for triggered modes.
+const ModeTriggeredMask Mode = 0x4
+
+// ModeTriggered returns true if the mode is a triggered mode.
+func ModeTriggered(m Mode) bool {
+	return m != ModePowerDown && m&ModeTriggeredMask == 0
+}
+
+func (m Mode) RegisterValue() uint16 {
+	return uint16(m)
+}
+
+// Calibration is the calibration register for the INA219. Values from:
+// https://github.com/adafruit/Adafruit_INA219/blob/master/Adafruit_INA219.cpp
+type Calibration uint16
+
+const (
+	Calibration32V2A    Calibration = 4096
+	Calibration32V1A    Calibration = 10240
+	Calibration16V400mA Calibration = 8192
+)
+
+func (c Calibration) RegisterValue() uint16 {
+	return uint16(c)
+}