Add driver for TMP102 low-power digital temperature sensor (#141)

* tmp102: add driver and example

tmp102/registers.go

@@ -0,0 +1,18 @@
+package tmp102
+
+const (
+	// Default I2C address
+	Address = 0x48
+
+	// Temperature register address
+	RegTemperature = 0x00
+
+	// Configuration register address
+	RegConfiguration = 0x01
+
+	// Low limit register address
+	RegLimitLow = 0x02
+
+	// High limit register address
+	RegLimitHigh = 0x03
+)

tmp102/tmp102.go

@@ -0,0 +1,58 @@
+// Package tmp102 implements a driver for the TMP102 digital temperature sensor.
+//
+// Datasheet: https://download.mikroe.com/documents/datasheets/tmp102-data-sheet.pdf
+
+package tmp102 // import "tinygo.org/x/drivers/tmp102"
+
+import (
+	"machine"
+)
+
+// Device holds the already configured I2C bus and the address of the sensor.
+type Device struct {
+	bus     machine.I2C
+	address uint8
+}
+
+// Config is the configuration for the TMP102.
+type Config struct {
+	Address uint8
+}
+
+// New creates a new TMP102 connection. The I2C bus must already be configured.
+func New(bus machine.I2C) Device {
+	return Device{
+		bus: bus,
+	}
+}
+
+// Configure initializes the sensor with the given parameters.
+func (d *Device) Configure(cfg Config) {
+	if cfg.Address == 0 {
+		cfg.Address = Address
+	}
+
+	d.address = cfg.Address
+}
+
+// Reads the temperature from the sensor and returns it in celsius milli degrees (°C/1000).
+func (d *Device) ReadTemperature() (temperature int32, err error) {
+
+	tmpData := make([]byte, 2)
+
+	err = d.bus.ReadRegister(d.address, RegTemperature, tmpData)
+
+	if err != nil {
+		return
+	}
+
+	temperatureSum := int32((int16(tmpData[0])<<8 | int16(tmpData[1])) >> 4)
+
+	if (temperatureSum & int32(1<<11)) == int32(1<<11) {
+		temperatureSum |= int32(0xf800)
+	}
+
+	temperature = temperatureSum * 625
+
+	return temperature / 10, nil
+}