servo: add function SetAngle() to simplify API for most common use case

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

examples/servo/servo.go

@@ -25,19 +25,25 @@ func main() {
 		return
 	}
 
+	for {
 		println("setting to 0°")
-	s.SetMicroseconds(1000)
+		s.SetAngle(0)
 		time.Sleep(3 * time.Second)
 
 		println("setting to 45°")
-	s.SetMicroseconds(1500)
+		s.SetAngle(45)
 		time.Sleep(3 * time.Second)
 
 		println("setting to 90°")
-	s.SetMicroseconds(2000)
+		s.SetAngle(90)
 		time.Sleep(3 * time.Second)
 
-	for {
-		time.Sleep(time.Second)
+		println("setting to 135°")
+		s.SetAngle(135)
+		time.Sleep(3 * time.Second)
+
+		println("setting to 180°")
+		s.SetAngle(180)
+		time.Sleep(3 * time.Second)
 	}
 }

servo/servo.go

@@ -1,6 +1,12 @@
 package servo
 
-import "machine"
+import (
+	"machine"
+
+	"errors"
+)
+
+var ErrInvalidAngle = errors.New("servo: invalid angle")
 
 // PWM is the interface necessary for controlling typical servo motors.
 type PWM interface {
@@ -80,3 +86,19 @@ func (s Servo) SetMicroseconds(microseconds int16) {
 	value := uint64(s.pwm.Top()) * uint64(microseconds) / (pwmPeriod / 1000)
 	s.pwm.Set(s.channel, uint32(value))
 }
+
+// SetAngle sets the angle of the servo in degrees. The angle should be between
+// 0 and 180, where 0 is the minimum angle and 180 is the maximum angle.
+// This function should work for most servos, but if it doesn't work for yours
+// you can use SetMicroseconds directly instead.
+func (s Servo) SetAngle(angle int) error {
+	if angle < 0 || angle > 180 {
+		return ErrInvalidAngle
+	}
+
+	// 0° is 1000µs, 180° is 2000µs. See explanation in SetMicroseconds.
+	microseconds := angle*1000/180 + 1000
+	s.SetMicroseconds(int16(microseconds))
+
+	return nil
+}