Andrew Russell / Servo

A very simple wrapper around the PWM library.

Dependents:   JS_1motor_20170707_ok Task_1_BallRidingbot_KeepingStationCatching_layingDown_1230 Task_2_BallRidingbot_MovingForwardCatching_backward_1230 testSSWMR_StationKeeping_200170830_OK ... more

This is my own wrapper around the PWM library. It handles servos with very long pulse intervals much better. It doesn't HAVE to be used with a servo, but I'm not too sure what else you could use it for. In any case, you're welcome to use it for whatever purpose you want.

Example code is shown below:

#include "mbed.h"
#include "Servo.h"

Servo servo(p26);

int main(void) {
	// .calibrate(pulse interval, minimum pulse width, maximum pulse width)
	servo.calibrate(0.02, 0.05*0.02, 0.10*0.02);
	float val = 0.0;
	while(1) {
		servo.write(val);
		val = val < 1.0 ? val + 0.1 : 0;
		wait(1);
	}
}

Servo.cpp

Committer:
andrewrussell
Date:
2013-02-15
Revision:
2:4c315bcd91b4
Parent:
1:c1b2ec2662fd

File content as of revision 2:4c315bcd91b4:

#include "Servo.h"
#include "mbed.h"

/**
 * Servo constructor
 *
 * Initialize variables, attach to a PWM-enabled pin.
 */
Servo::Servo(PinName pwm32) : _pwm(pwm32) {
    _period = 0;
    _min = 0;
    _max = 0;
    _pos = 0;
    invert = 0;
}

/**
 * float read
 *
 * Read the value shat should be at the servo.
 */
float Servo::read(void) {
    return _pos;
}

/**
 * void write
 *
 * Write a value to the servo
 *
 * @param float to Positional data taking values of 0.0 to 1.0.
 */
void Servo::write(float to) {
    if(to < 0 || to > 1) return;
    _pos = to;
    float dest_pw;
    if(invert == 0) {
        dest_pw = to * _slope + _min;
    }
    else if(invert == 1) {
        dest_pw = to * -_slope + _max;
    }
    else { return; }
    _pwm.pulsewidth(dest_pw);
}

/**
 * void calibrate
 *
 * Set the limits of the PWM.
 *
 * @param float period Pulse period in seconds
 * @param float max Maximum pulse width in seconds
 * @param float min Minimum pulse width in seconds
 */
void Servo::calibrate(float period, float min, float max) {
    _period = period;
    _min = min;
    _max = max;
    _slope = max - min;
    
    _pwm.period(_period);
}