Stanley Setiawan

Important changes to forums and questions

All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.

6 years, 7 months ago.

Help with Servo.read() function

Hi there!

I am currently trying to use a servo motor library:

Servo Library https://os.mbed.com/users/simon/code/Servo/ Servo library

It works fine with everything except with the .read() function. I put the output to a serial output to see the output. It is not showing what is the current condition, and just showed "0.5000" not the real value, like in the picture I attach below:

/media/uploads/stanleyaley/delsoon.png

The code is:

Servo - trial using Servo.h as the library

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

Servo myservo(PWM_OUT);
Serial pc(USBTX, USBRX);

int main() {
	float range = 0.0005;
	float position = 0.5;
	float state = 0.1f;
	printf("I am on\n");
	myservo.calibrate (range, 90.0);
	
	
	while (1){
		pc.printf("start new!");
		myservo = 0.5;
		wait(1);
		state = myservo.read();
		pc.printf("Current: %.5f \n", state);
		state = 0;
		wait(1);

		myservo.position(-45);
		wait(1);
		state = myservo.read();
		pc.printf("Current: %.5f \n", state);
		state = 0;
		wait(1);

		myservo.position(0);
		wait(1);
		state = myservo.read();
		pc.printf("Current: %.5f \n", state);
		state = 0;
		wait(1);

		myservo.position(30);
		wait(1);
		state = myservo.read();
		pc.printf("Current: %.2f \n", state);
		state = 0;
		wait(1);

		myservo.position(45);
		wait(1);
		state = myservo.read();
		pc.printf("Current: %.2f \n", state);
		state = 0;
		wait(1);

		myservo.position(90);
		wait(1);
		state = myservo.read();
		pc.printf("Current: %.2f \n", state);
		state = 0;
		wait(1);
	}
}

If someone can help me, it'll be really great!

Thank you soo much for your help!

Cheers!

1 Answer

Chris Albertson
6 years, 7 months ago.

I looked at the definition of the position() method. It does not save the position _p so that it can be read back with read. Seems like a bug.

it you were to use "write" in place of "position" then "read" might work.

It would be an easy fix to the library. the position() methane needs to compute and save a value in _p

It is a one line fix.