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().

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.