Add I2C INA219 driver (#705)

INA219: add INA219 driver

ina219/ina219.go

@@ -0,0 +1,202 @@
+package ina219
+
+import (
+	"tinygo.org/x/drivers"
+	"tinygo.org/x/drivers/internal/legacy"
+)
+
+// An INA219 device.
+type Device struct {
+	bus     drivers.I2C
+	Address uint16
+	config  Config
+}
+
+// Create a new INA219 device with the default configuration
+// and the given I2C bus at the default address.
+//
+// Set Address after New to change the address.
+//
+// Call Configure after New to write the configuration to the
+// device. If you don't call Configure, the device may have a
+// different configuration and the power divider and current
+// multiplier are probably wrong.
+func New(bus drivers.I2C) Device {
+	return Device{
+		bus:     bus,
+		Address: Address,
+		config:  Config32V2A,
+	}
+}
+
+// Set the configuration for the device. This only changes the
+// configuration in memory, not on the device. Call Configure
+// to write the configuration to the device.
+func (d *Device) SetConfig(config Config) {
+	d.config = config
+}
+
+// Write the current configuration to the device.
+func (d *Device) Configure() (err error) {
+	if err = d.WriteRegister(
+		RegConfig,
+		d.config.RegisterValue(),
+	); err != nil {
+		return
+	}
+
+	if err = d.WriteRegister(
+		RegCalibration,
+		d.config.Calibration.RegisterValue(),
+	); err != nil {
+		return
+	}
+
+	var readConfig Config
+	// make sure the configuration is read back correctly
+	if readConfig, err = d.ReadConfig(); err != nil {
+		return
+	} else if readConfig.RegisterValue() != d.config.RegisterValue() {
+		err = ErrConfigMismatch{}
+	} else if readConfig.Calibration.RegisterValue() != d.config.Calibration.RegisterValue() {
+		err = ErrConfigMismatch{}
+	}
+
+	return
+}
+
+// Trigger a conversion. This is only necessary if the device is in
+// trigger mode. In continuous mode (the default), the device will
+// automatically trigger conversions and this has no effect. See
+// config.go.
+//
+// Triggering a conversion or reading the "power" register resets
+// the conversion ready bit.
+func (d *Device) Trigger() (err error) {
+	// Only trigger if the mode is one of the triggered modes.
+	if ModeTriggered(d.config.Mode) {
+		err = d.WriteRegister(RegConfig, d.config.RegisterValue())
+	}
+	return
+}
+
+// Measurements reads the bus voltage, shunt voltage, current, and power
+// from the device.
+func (d *Device) Measurements() (
+	busVoltage int16,
+	shuntVoltage int16,
+	current float32,
+	power float32,
+	err error,
+) {
+	// Attempt to read bus voltage first, so we can check for overflow
+	// or conversion not ready.
+	if busVoltage, err = d.BusVoltage(); err != nil {
+		return
+	}
+
+	// Read the rest of the values, reading Power last, which resets
+	// the conversion ready bit (relevant for triggered modes).
+	if shuntVoltage, err = d.ShuntVoltage(); err != nil {
+		return
+	}
+
+	if current, err = d.Current(); err != nil {
+		return
+	}
+
+	if power, err = d.Power(); err != nil {
+		return
+	}
+
+	return
+}
+
+// BusVoltage reads the "bus" voltage in millivolts.
+//
+// It returns an error if the value is invalid due to overflow
+// or if the conversion is not ready yet. In a continuous mode
+// there should always be a measurement available after the
+// device is ready. See above notes on Trigger.
+func (d *Device) BusVoltage() (voltage int16, err error) {
+	val, err := d.ReadRegister(RegBusVoltage)
+	if err != nil {
+		return
+	}
+
+	// The overflow bit is set, so the values are invalid.
+	if val&(1<<0) != 0 {
+		err = ErrOverflow{}
+		return
+	}
+
+	// The conversion is not ready yet.
+	if ModeTriggered(d.config.Mode) && val&(1<<1) != 0 {
+		err = ErrNotReady{}
+		return
+	}
+
+	voltage = (int16(val) >> 3) * 4
+	return
+}
+
+// ShuntVoltage reads the "shunt" voltage in 100ths of a millivolt.
+func (d *Device) ShuntVoltage() (voltage int16, err error) {
+	return d.ReadRegister(RegShuntVoltage)
+}
+
+// Current reads the current in milliamps.
+func (d *Device) Current() (current float32, err error) {
+	val, err := d.ReadRegister(RegCurrent)
+	if err != nil {
+		return
+	}
+
+	current = float32(val) / d.config.CurrentDivider
+	return
+}
+
+// Power reads the power in milliwatts.
+func (d *Device) Power() (power float32, err error) {
+	val, err := d.ReadRegister(RegPower)
+	if err != nil {
+		return
+	}
+
+	power = float32(val) * d.config.PowerMultiplier
+	return
+}
+
+// Read the configuration from the device.
+func (d *Device) ReadConfig() (config Config, err error) {
+	var cfg, cal int16
+	if cfg, err = d.ReadRegister(RegConfig); err != nil {
+		return
+	}
+
+	if cal, err = d.ReadRegister(RegCalibration); err != nil {
+		return
+	}
+
+	config = NewConfig(cfg, cal)
+	return
+}
+
+// Read a register from the device.
+func (d *Device) ReadRegister(reg uint8) (val int16, err error) {
+	buf := make([]byte, 2)
+
+	err = legacy.ReadRegister(d.bus, uint8(d.Address), reg, buf)
+	if err != nil {
+		return
+	}
+
+	val = int16(buf[0])<<8 | int16(buf[1]&0xff)
+	return
+}
+
+// Write to a register on the device.
+func (d *Device) WriteRegister(reg uint8, val uint16) error {
+	buf := []byte{byte(val >> 8), byte(val & 0xff)}
+	return legacy.WriteRegister(d.bus, uint8(d.Address), reg, buf)
+}