all: introduce a temperature type

This type should be used whenever a sensor (or actuator?) works with a
temperature. For example, this commit changes the signature:

    ReadTemperature() (int32, error)

to the following:

    ReadTemperature() (drivers.Temperature, error)

I believe this is much clearer in intent. It also makes it trivial to
introduce common conversions. For example, there are already Celsius()
and Fahrenheit() methods to convert to the given units, as a floating
point. More units could be added as needed, for example a CelsiusInt().

Makefile

@@ -214,6 +214,6 @@ NOTESTS = build examples flash semihosting pcd8544 shiftregister st7789 micropho
 TESTS = $(filter-out $(addsuffix /%,$(NOTESTS)),$(DRIVERS))
 
 unit-test:
-	@go test -v $(addprefix ./,$(TESTS)) 
+	@go test -v . $(addprefix ./,$(TESTS)) 
 
 test: clean fmt-check unit-test smoke-test

adt7410/adt7410.go

@@ -60,19 +60,8 @@ func (d *Device) Connected() bool {
 }
 
 // ReadTemperature returns the temperature in celsius milli degrees (°C/1000)
-func (d *Device) ReadTemperature() (temperature int32, err error) {
-	return (int32(d.readUint16(RegTempValueMSB)) * 1000) / 128, nil
-}
-
-// ReadTempC returns the value in the temperature value register, in Celsius.
-func (d *Device) ReadTempC() float32 {
-	t := d.readUint16(RegTempValueMSB)
-	return float32(int(t)) / 128.0
-}
-
-// ReadTempF returns the value in the temperature value register, in Fahrenheit.
-func (d *Device) ReadTempF() float32 {
-	return d.ReadTempC()*1.8 + 32.0
+func (d *Device) ReadTemperature() (temperature drivers.Temperature, err error) {
+	return (drivers.Temperature(d.readUint16(RegTempValueMSB)) * 1000) / 128, nil
 }
 
 func (d *Device) writeByte(reg uint8, data byte) {

bme280/bme280.go

@@ -114,14 +114,14 @@ func (d *Device) Reset() {
 }
 
 // ReadTemperature returns the temperature in celsius milli degrees (°C/1000)
-func (d *Device) ReadTemperature() (int32, error) {
+func (d *Device) ReadTemperature() (drivers.Temperature, error) {
 	data, err := d.readData()
 	if err != nil {
 		return 0, err
 	}
 
 	temp, _ := d.calculateTemp(data)
-	return temp, nil
+	return drivers.Temperature(temp), nil
 }
 
 // ReadPressure returns the pressure in milli pascals mPa

bmi160/bmi160.go

@@ -81,7 +81,7 @@ func (d *DeviceSPI) Reset() error {
 }
 
 // ReadTemperature returns the temperature in celsius milli degrees (°C/1000).
-func (d *DeviceSPI) ReadTemperature() (temperature int32, err error) {
+func (d *DeviceSPI) ReadTemperature() (temperature drivers.Temperature, err error) {
 	data := d.buf[:3]
 	data[0] = 0x80 | reg_TEMPERATURE_0
 	data[1] = 0
@@ -109,7 +109,7 @@ func (d *DeviceSPI) ReadTemperature() (temperature int32, err error) {
 	//    rawTemperature * 1000 * 64 / 0x8000 + 23000
 	//    rawTemperature * 64000 / 0x8000 + 23000
 	//    rawTemperature * 125 / 64 + 23000
-	temperature = int32(rawTemperature)*125/64 + 23000
+	temperature = drivers.Temperature(rawTemperature)*125/64 + 23000
 	return
 }
 

bmp180/bmp180.go

@@ -81,14 +81,14 @@ func (d *Device) Configure() {
 }
 
 // ReadTemperature returns the temperature in celsius milli degrees (°C/1000).
-func (d *Device) ReadTemperature() (temperature int32, err error) {
+func (d *Device) ReadTemperature() (temperature drivers.Temperature, err error) {
 	rawTemp, err := d.rawTemp()
 	if err != nil {
 		return
 	}
 	b5 := d.calculateB5(rawTemp)
 	t := (b5 + 8) >> 4
-	return 100 * t, nil
+	return drivers.Temperature(100 * t), nil
 }
 
 // ReadPressure returns the pressure in milli pascals (mPa).

bmp280/bmp280.go

@@ -132,7 +132,7 @@ func (d *Device) PrintCali() {
 }
 
 // ReadTemperature returns the temperature in celsius milli degrees (°C/1000).
-func (d *Device) ReadTemperature() (temperature int32, err error) {
+func (d *Device) ReadTemperature() (temperature drivers.Temperature, err error) {
 	data, err := d.readData(REG_TEMP, 3)
 	if err != nil {
 		return
@@ -150,7 +150,7 @@ func (d *Device) ReadTemperature() (temperature int32, err error) {
 
 	// Convert from degrees to milli degrees by multiplying by 10.
 	// Will output 30250 milli degrees celsius for 30.25 degrees celsius
-	temperature = 10 * ((tFine*5 + 128) >> 8)
+	temperature = drivers.Temperature(10 * ((tFine*5 + 128) >> 8))
 	return
 }
 

bmp388/bmp388.go

@@ -133,16 +133,16 @@ func (d *Device) tlinCompensate() (int64, error) {
 
 }
 
-// ReadTemperature returns the temperature in centicelsius, i.e 2426 / 100 = 24.26 C
-func (d *Device) ReadTemperature() (int32, error) {
+// ReadTemperature returns the temperature in milli degrees Celsius, i.e 24260 / 1000 = 24.26°C.
+func (d *Device) ReadTemperature() (drivers.Temperature, error) {
 
 	tlin, err := d.tlinCompensate()
 	if err != nil {
 		return 0, err
 	}
 
-	temp := (tlin * 25) / 16384
-	return int32(temp), nil
+	temp := (tlin * 125) / 8192
+	return drivers.Temperature(temp), nil
 }
 
 // ReadPressure returns the pressure in centipascals, i.e 10132520 / 100 = 101325.20 Pa

dht/constants.go

@@ -35,18 +35,6 @@ func (d DeviceType) extractData(buf []byte) (temp int16, hum uint16) {
 	return
 }
 
-// Celsius and Fahrenheit temperature scales
-type TemperatureScale uint8
-
-func (t TemperatureScale) convertToFloat(temp int16) float32 {
-	if t == C {
-		return float32(temp) / 10
-	} else {
-		// Fahrenheit
-		return float32(temp)*(9.0/50.) + 32.
-	}
-}
-
 // All functions return ErrorCode instance as error. This class can be used for more efficient error processing
 type ErrorCode uint8
 
@@ -57,9 +45,6 @@ const (
 	DHT11 DeviceType = iota
 	DHT22
 
-	C TemperatureScale = iota
-	F
-
 	ChecksumError ErrorCode = iota
 	NoSignalError
 	NoDataError

dht/thermometer.go

@@ -9,14 +9,15 @@ package dht // import "tinygo.org/x/drivers/dht"
 import (
 	"machine"
 	"time"
+
+	"tinygo.org/x/drivers"
 )
 
 // DummyDevice provides a basic interface for DHT devices.
 type DummyDevice interface {
 	ReadMeasurements() error
 	Measurements() (temperature int16, humidity uint16, err error)
-	Temperature() (int16, error)
-	TemperatureFloat(scale TemperatureScale) (float32, error)
+	Temperature() (drivers.Temperature, error)
 	Humidity() (uint16, error)
 	HumidityFloat() (float32, error)
 }
@@ -49,23 +50,13 @@ func (t *device) ReadMeasurements() error {
 	return err
 }
 
-// Getter for temperature. Temperature method returns temperature as it is sent by device.
-// The temperature is measured temperature in Celsius multiplied by 10.
+// Getter for temperature. The temperature is returned in milli degrees Celsius.
 // If no successful measurements for this device was performed, returns UninitializedDataError.
-func (t *device) Temperature() (int16, error) {
+func (t *device) Temperature() (drivers.Temperature, error) {
 	if !t.initialized {
 		return 0, UninitializedDataError
 	}
-	return t.temperature, nil
-}
-
-// Getter for temperature. TemperatureFloat returns temperature in a given scale.
-// If no successful measurements for this device was performed, returns UninitializedDataError.
-func (t *device) TemperatureFloat(scale TemperatureScale) (float32, error) {
-	if !t.initialized {
-		return 0, UninitializedDataError
-	}
-	return scale.convertToFloat(t.temperature), nil
+	return drivers.Temperature(t.temperature) * 100, nil
 }
 
 // Getter for humidity. Humidity returns humidity as it is sent by device.

dht/timesafethermometer.go

@@ -9,6 +9,8 @@ package dht // import "tinygo.org/x/drivers/dht"
 import (
 	"machine"
 	"time"
+
+	"tinygo.org/x/drivers"
 )
 
 // Device interface provides main functionality of the DHTXX sensors.
@@ -35,10 +37,9 @@ func (m *managedDevice) Measurements() (temperature int16, humidity uint16, err
 	return m.t.Measurements()
 }
 
-// Getter for temperature. Temperature method returns temperature as it is sent by device.
-// The temperature is measured temperature in Celsius multiplied by 10.
+// Getter for temperature. The temperature is returned in milli degrees Celsius.
 // Depending on the UpdatePolicy of the device may update cached measurements.
-func (m *managedDevice) Temperature() (temp int16, err error) {
+func (m *managedDevice) Temperature() (temp drivers.Temperature, err error) {
 	err = m.checkForUpdateOnDataRequest()
 	if err != nil {
 		return 0, err
@@ -64,16 +65,6 @@ func (m *managedDevice) checkForUpdateOnDataRequest() (err error) {
 	return err
 }
 
-// Getter for temperature. TemperatureFloat returns temperature in a given scale.
-// Depending on the UpdatePolicy of the device may update cached measurements.
-func (m *managedDevice) TemperatureFloat(scale TemperatureScale) (float32, error) {
-	err := m.checkForUpdateOnDataRequest()
-	if err != nil {
-		return 0, err
-	}
-	return m.t.TemperatureFloat(scale)
-}
-
 // Getter for humidity. Humidity returns humidity as it is sent by device.
 // The humidity is measured in percentages multiplied by 10.
 // Depending on the UpdatePolicy of the device may update cached measurements.

ds3231/ds3231.go

@@ -134,13 +134,13 @@ func (d *Device) ReadTime() (dt time.Time, err error) {
 }
 
 // ReadTemperature returns the temperature in millicelsius (mC)
-func (d *Device) ReadTemperature() (int32, error) {
+func (d *Device) ReadTemperature() (drivers.Temperature, error) {
 	data := make([]uint8, 2)
 	err := d.bus.ReadRegister(uint8(d.Address), REG_TEMP, data)
 	if err != nil {
 		return 0, err
 	}
-	return int32(data[0])*1000 + int32((data[1]>>6)*25)*10, nil
+	return drivers.Temperature(int32(data[0])*1000 + int32((data[1]>>6)*25)*10), nil
 }
 
 // uint8ToBCD converts a byte to BCD for the DS3231

examples/adt7410/main.go

@@ -19,8 +19,8 @@ func main() {
 	sensor.Configure()
 
 	for {
-		temp := sensor.ReadTempF()
-		fmt.Printf("temperature: %f\r\n", temp)
+		temp, _ := sensor.ReadTemperature()
+		fmt.Printf("temperature: %f°C\r\n", temp.Celsius())
 		time.Sleep(time.Second)
 	}
 

examples/bme280/main.go

@@ -22,7 +22,7 @@ func main() {
 
 	for {
 		temp, _ := sensor.ReadTemperature()
-		println("Temperature:", strconv.FormatFloat(float64(temp)/1000, 'f', 2, 64), "°C")
+		println("Temperature:", strconv.FormatFloat(float64(temp.Celsius()), 'f', 2, 64), "°C")
 		press, _ := sensor.ReadPressure()
 		println("Pressure:", strconv.FormatFloat(float64(press)/100000, 'f', 2, 64), "hPa")
 		hum, _ := sensor.ReadHumidity()

examples/bmi160/main.go

@@ -27,7 +27,7 @@ func main() {
 			println("Error reading temperature", err)
 			continue
 		}
-		fmt.Printf("Temperature: %.2f °C\n", float32(t)/1000)
+		fmt.Printf("Temperature: %.2f °C\n", t.Celsius())
 
 		accelX, accelY, accelZ, err := sensor.ReadAcceleration()
 		if err != nil {

examples/bmp180/main.go

@@ -22,7 +22,7 @@ func main() {
 
 	for {
 		temp, _ := sensor.ReadTemperature()
-		println("Temperature:", float32(temp)/1000, "°C")
+		println("Temperature:", temp.Celsius(), "°C")
 
 		pressure, _ := sensor.ReadPressure()
 		println("Pressure", float32(pressure)/100000, "hPa")

examples/bmp280/main.go

@@ -30,7 +30,7 @@ func main() {
 			println("Error reading temperature")
 		}
 		// Temperature in degrees Celsius
-		fmt.Printf("Temperature: %.2f °C\n", float32(t)/1000)
+		fmt.Printf("Temperature: %.2f °C\n", t.Celsius())
 
 		p, err := sensor.ReadPressure()
 		if err != nil {

examples/bmp388/main.go

@@ -38,13 +38,13 @@ func main() {
 	}
 
 	for {
-		temp, err := sensor.ReadTemperature() // returns the temperature in centicelsius
+		temp, err := sensor.ReadTemperature() // returns the temperature in millicelsius
 		press, err := sensor.ReadPressure()   // returns the pressure in centipascals
 
 		if err != nil {
 			println(err)
 		} else {
-			println("Temperature: " + strconv.FormatInt(int64(temp), 10) + " cC")
+			println("Temperature:", temp/1000, "C")
 			println("Pressure:    " + strconv.FormatInt(int64(press), 10) + " cPa\n")
 		}
 

examples/ds3231/main.go

@@ -38,7 +38,7 @@ func main() {
 			fmt.Printf("Date: %d/%s/%02d %02d:%02d:%02d \r\n", dt.Year(), dt.Month(), dt.Day(), dt.Hour(), dt.Minute(), dt.Second())
 		}
 		temp, _ := rtc.ReadTemperature()
-		fmt.Printf("Temperature: %.2f °C \r\n", float32(temp)/1000)
+		fmt.Printf("Temperature: %.2f °C \r\n", temp.Celsius())
 
 		time.Sleep(time.Second * 1)
 	}

examples/lsm6ds3/main.go

@@ -23,8 +23,8 @@ func main() {
 		println("Acceleration:", float32(x)/1000000, float32(y)/1000000, float32(z)/1000000)
 		x, y, z = accel.ReadRotation()
 		println("Gyroscope:", float32(x)/1000000, float32(y)/1000000, float32(z)/1000000)
-		x, _ = accel.ReadTemperature()
-		println("Degrees C", float32(x)/1000, "\n\n")
+		t, _ := accel.ReadTemperature()
+		println("Degrees C", t.Celsius(), "\n\n")
 		time.Sleep(time.Millisecond * 1000)
 	}
 }

examples/lsm6dsox/main.go

@@ -6,6 +6,7 @@ import (
 	"machine"
 	"time"
 
+	"tinygo.org/x/drivers"
 	"tinygo.org/x/drivers/lsm6dsox"
 )
 
@@ -76,7 +77,7 @@ func calibrateGyro(device *lsm6dsox.Device) {
 }
 
 // Arduino IDE's Serial Plotter
-func printPlotter(ax, ay, az, gx, gy, gz, t int32) {
+func printPlotter(ax, ay, az, gx, gy, gz int32, t drivers.Temperature) {
 	if SHOW_ACCELERATION {
 		fmt.Printf("AX:%f, AY:%f, AZ:%f,", axis(ax, 0), axis(ay, 0), axis(az, 0))
 	}
@@ -84,7 +85,7 @@ func printPlotter(ax, ay, az, gx, gy, gz, t int32) {
 		fmt.Printf("GX:%f, GY:%f, GZ:%f,", axis(gx, cal[0]), axis(gy, cal[1]), axis(gz, cal[2]))
 	}
 	if SHOW_TEMPERATURE {
-		fmt.Printf("T:%f", float32(t)/1000)
+		fmt.Printf("T:%f", t.Celsius())
 	}
 	println()
 }

examples/mag3110/main.go

@@ -19,7 +19,7 @@ func main() {
 		println("Magnetic readings:", x, y, z)
 
 		c, _ := mag.ReadTemperature()
-		println("Temperature:", float32(c)/1000, "°C")
+		println("Temperature:", c.Celsius(), "°C")
 
 		time.Sleep(time.Millisecond * 100)
 	}

examples/tmp102/main.go

@@ -20,7 +20,7 @@ func main() {
 
 		temp, _ := thermo.ReadTemperature()
 
-		print(fmt.Sprintf("%.2f°C\r\n", float32(temp)/1000.0))
+		print(fmt.Sprintf("%.2f°C\r\n", temp.Celsius()))
 
 		time.Sleep(time.Millisecond * 1000)
 	}

lsm303agr/lsm303agr.go

@@ -191,14 +191,14 @@ func (d *Device) ReadCompass() (h int32) {
 }
 
 // ReadTemperature returns the temperature in Celsius milli degrees (°C/1000)
-func (d *Device) ReadTemperature() (c int32, e error) {
+func (d *Device) ReadTemperature() (c drivers.Temperature, e error) {
 
 	data1, data2 := []byte{0}, []byte{0}
 	d.bus.ReadRegister(uint8(d.AccelAddress), OUT_TEMP_H_A, data1)
 	d.bus.ReadRegister(uint8(d.AccelAddress), OUT_TEMP_L_A, data2)
 
 	t := int16((uint16(data1[0])<<8 | uint16(data2[0]))) >> 4 // temperature offsef from 25 °C
-	c = int32((float32(25) + float32(t)/8) * 1000)
+	c = drivers.Temperature(t)*125 + 25000
 	e = nil
 	return
 }

lsm6ds3/lsm6ds3.go

@@ -165,13 +165,13 @@ func (d *Device) ReadRotation() (x int32, y int32, z int32) {
 }
 
 // ReadTemperature returns the temperature in celsius milli degrees (°C/1000)
-func (d *Device) ReadTemperature() (int32, error) {
+func (d *Device) ReadTemperature() (drivers.Temperature, error) {
 	d.bus.ReadRegister(uint8(d.Address), OUT_TEMP_L, d.dataBufferTwo)
 
 	// From "Table 5. Temperature sensor characteristics"
 	// temp = value/16 + 25
 	t := 25000 + (int32(int16((int16(d.dataBufferTwo[1])<<8)|int16(d.dataBufferTwo[0])))*125)/2
-	return t, nil
+	return drivers.Temperature(t), nil
 }
 
 // ReadSteps returns the steps of the pedometer

lsm6dsox/lsm6dsox.go

@@ -110,11 +110,11 @@ func (d *Device) ReadRotation() (x int32, y int32, z int32) {
 }
 
 // ReadTemperature returns the temperature in celsius milli degrees (°C/1000)
-func (d *Device) ReadTemperature() (int32, error) {
+func (d *Device) ReadTemperature() (drivers.Temperature, error) {
 	d.bus.ReadRegister(uint8(d.Address), OUT_TEMP_L, d.dataBufferTwo)
 
 	// From "Table 4. Temperature sensor characteristics"
 	// temp = value/256 + 25
 	t := 25000 + (int32(int16((int16(d.dataBufferTwo[1])<<8)|int16(d.dataBufferTwo[0])))*125)/32
-	return t, nil
+	return drivers.Temperature(t), nil
 }

mag3110/mag3110.go

@@ -49,8 +49,8 @@ func (d Device) ReadMagnetic() (x int16, y int16, z int16) {
 
 // ReadTemperature reads and returns the current die temperature in
 // celsius milli degrees (°C/1000).
-func (d Device) ReadTemperature() (int32, error) {
+func (d Device) ReadTemperature() (drivers.Temperature, error) {
 	data := make([]byte, 1)
 	d.bus.ReadRegister(uint8(d.Address), DIE_TEMP, data)
-	return int32(data[0]) * 1000, nil
+	return drivers.Temperature(data[0]) * 1000, nil
 }

sht3x/sht3x.go

@@ -31,9 +31,9 @@ func New(bus drivers.I2C) Device {
 }
 
 // Read returns the temperature in celsius milli degrees (°C/1000).
-func (d *Device) ReadTemperature() (tempMilliCelsius int32, err error) {
+func (d *Device) ReadTemperature() (tempMilliCelsius drivers.Temperature, err error) {
 	tempMilliCelsius, _, err = d.ReadTemperatureHumidity()
-	return tempMilliCelsius, err
+	return drivers.Temperature(tempMilliCelsius), err
 }
 
 // Read returns the relative humidity in hundredths of a percent.
@@ -43,15 +43,15 @@ func (d *Device) ReadHumidity() (relativeHumidity int16, err error) {
 }
 
 // Read returns both the temperature and relative humidity.
-func (d *Device) ReadTemperatureHumidity() (tempMilliCelsius int32, relativeHumidity int16, err error) {
+func (d *Device) ReadTemperatureHumidity() (tempMilliCelsius drivers.Temperature, relativeHumidity int16, err error) {
 	var rawTemp, rawHum, errx = d.rawReadings()
 	if errx != nil {
 		err = errx
 		return
 	}
-	tempMilliCelsius = (35000 * int32(rawTemp) / 13107) - 45000
+	tempMilliCelsius = drivers.Temperature((35000 * int32(rawTemp) / 13107) - 45000)
 	relativeHumidity = int16(2000 * int32(rawHum) / 13107)
-	return tempMilliCelsius, relativeHumidity, err
+	return
 }
 
 // rawReadings returns the sensor's raw values of the temperature and humidity

thermistor/thermistor.go

@@ -29,6 +29,8 @@ package thermistor // import "tinygo.org/x/drivers/thermistor"
 import (
 	"machine"
 	"math"
+
+	"tinygo.org/x/drivers"
 )
 
 // Device holds the ADC pin and the needed settings for calculating the
@@ -61,7 +63,7 @@ func (d *Device) Configure() {
 }
 
 // ReadTemperature returns the temperature in celsius milli degrees (°C/1000)
-func (d *Device) ReadTemperature() (temperature int32, err error) {
+func (d *Device) ReadTemperature() (temperature drivers.Temperature, err error) {
 	var reading uint32
 	if d.HighSide {
 		// Thermistor connected from analog input to high logic level.
@@ -82,5 +84,5 @@ func (d *Device) ReadTemperature() (temperature int32, err error) {
 	steinhart = 1.0 / steinhart                                 // Invert
 	steinhart -= 273.15                                         // convert to C
 
-	return int32(steinhart * 1000), nil
+	return drivers.Temperature(steinhart * 1000), nil
 }

tmp102/tmp102.go

@@ -46,7 +46,7 @@ func (d *Device) Connected() bool {
 }
 
 // Reads the temperature from the sensor and returns it in celsius milli degrees (°C/1000).
-func (d *Device) ReadTemperature() (temperature int32, err error) {
+func (d *Device) ReadTemperature() (temperature drivers.Temperature, err error) {
 
 	tmpData := make([]byte, 2)
 
@@ -62,7 +62,7 @@ func (d *Device) ReadTemperature() (temperature int32, err error) {
 		temperatureSum |= int32(0xf800)
 	}
 
-	temperature = temperatureSum * 625
+	temperature = drivers.Temperature(temperatureSum * 625 / 10)
 
-	return temperature / 10, nil
+	return temperature, nil
 }

units.go

@@ -0,0 +1,17 @@
+package drivers
+
+// This file contains some common units that can be used in a sensor driver.
+
+// Temperature is a temperature in Celsius milli degrees (°C/1000). For example,
+// the value 25000 is 25°C.
+type Temperature int32
+
+// Celsius returns the temperature in degrees Celsius.
+func (t Temperature) Celsius() float32 {
+	return float32(t) / 1000
+}
+
+// Fahrenheit returns the temperature in degrees Fahrenheit.
+func (t Temperature) Fahrenheit() float32 {
+	return t.Celsius()*1.8 + 32
+}

units_test.go

@@ -0,0 +1,26 @@
+package drivers
+
+import "testing"
+
+func TestTemperature(t *testing.T) {
+	tests := []struct {
+		t Temperature
+		c float32 // Celsius
+		f float32 // Fahrenheit
+	}{
+		{-40000, -40, -40}, // -40°C
+		{0, 0, 32},         // 0°C
+		{20000, 20, 68},    // 20°C
+		{25000, 25, 77},    // 25°C
+	}
+	for _, tc := range tests {
+		c := tc.t.Celsius()
+		f := tc.t.Fahrenheit()
+		if c != tc.c {
+			t.Errorf("expected value %d to be %f°C, but got %f°C", tc.t, tc.c, c)
+		}
+		if f != tc.f {
+			t.Errorf("expected value %d to be %f°F, but got %f°F", tc.t, tc.f, f)
+		}
+	}
+}