mag3110: change method name/signature for obtaining temperature to be uniform with other similar drivers

Signed-off-by: Ron Evans <ron@hybridgroup.com>

examples/mag3110/main.go

@@ -16,7 +16,11 @@ func main() {
 
 	for {
 		x, y, z := mag.ReadMagnetic()
-		println(x, y, z)
+		println("Magnetic readings:", x, y, z)
+
+		c, _ := mag.ReadTemperature()
+		println("Temperature:", float32(c)/1000, "ºC")
+
 		time.Sleep(time.Millisecond * 100)
 	}
 }

mag3110/mag3110.go

@@ -48,9 +48,10 @@ func (d Device) ReadMagnetic() (x int16, y int16, z int16) {
 	return
 }
 
-// ReadTemperature reads the current die temperature in degrees Celsius.
-func (d Device) ReadTemperature() (temp int8) {
+// ReadTemperature reads and returns the current die temperature in
+// celsius milli degrees (ºC/1000).
+func (d Device) ReadTemperature() (int32, error) {
 	data := make([]byte, 1)
 	d.bus.ReadRegister(uint8(d.Address), DIE_TEMP, data)
-	return int8(data[0])
+	return int32(data[0]) * 1000, nil
 }