Servo

This documents the Servo library for controlling RC servomotors. It is implemented as a thin layer over the built-in timer peripherals.

You can use this library in the IDE by choosing the Servo item under the Sketch > Import Library... menu.

If you are using the Unix toolchain, the library is located in $LIB_MAPLE_HOME/libraries/Servo/.

Servo Class Reference

You can construct a Servo object by including the declaration

Servo servo;

in your sketch. This will create a Servo object called servo. You can then use any of its methods; for instance, to control a servomotor attached to pin 9, you could write

servo.attach(9);

class Servo

Class for controlling RC servomotors via timers.

bool Servo::attach(uint8 pin, uint16 min, uint16 max)

Attach this Servo object to the given pin. The pin must be capable of PWM. You can check this by seeing if “PWM” is written next to its number on the Maple silkscreen, or by consulting the pwmWrite() documentation.

Sets this pin’s mode to PWM, and returns true if successful. Does nothing and returns false if the pin doesn’t support PWM.

Parameter min is the pulse width corresponding to 0 degrees; max is the pulse width corresponding to 180 degrees (both are in microseconds).

bool Servo::attach(uint8 pin)

Equivalent to attach(pin, 544, 2400).

int Servo::attached() const

If currently attached (via attach()) to a pin, returns that pin’s number. Returns NOT_ATTACHED otherwise.

bool Servo::detach()

If this Servo object is currently attached to pin, stops driving the servo by setting a zero pulse width (this is accomplished by setting the associated channel mode to TIMER_DISABLED).

Subsequently, calling attached() will return NOT_ATTACHED.

void Servo::write(unsigned int value)

If value is less than SERVO_MAX_WRITE_ANGLE (which, for Arduino compatibility, is 200), it’s interpreted as an angle in degrees. Otherwise, it’s treated as a pulse width in microseconds.

Drives the servo to target the given angle, based on a linear interpolation of the min and max pulse widths determined when attach() was called.

Be aware that some (especially lower-cost) servos have fairly non-linear maps between pulse width and target angle. Make sure to test your motor before relying on this method.

void Servo::writeMicroseconds(uint16 pulseWidth)

Drives the servo using a pulseWidth-microsecond pulse.

If pulseWidth is outside of the [min, max] pulse width range set during attach(), it will be clamped to lie in this range.

int Servo::read() const

Returns the servo’s target angle, in degrees. This will be clamped to lie between 0 (when the pulse width is at most min) and 180 (when the pulse width is at least max).

uint16 Servo::readMicroseconds() const

Returns the pulse width of the wave currently driving the servo, in microseconds. This will be clamped to lie in the [min, max] pulse width range set during attach().