Monday, May 30, 2011

10

LIBSSC32: ARDUINO + SSC32

Today I would like to share a library for Arduino that makes it easy to control a SSC32.

But, what is a SSC32?
The SSC32 is a Serial Servo Controller, capable of controlling up to 32 servo motors at a time. Very useful in robotic projects such as arms or humanoids.


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You can buy it at http://www.lynxmotion.com for about $40.  The thing about this piece of hardware is that it is very flexible. It is not only a servo controller, it also provides some pins where you can connect sensors and read  its values. And the most useful of its features (in my humble opinion) is that you can specify a group of servos, set each servo inside the group to move to a different location and specify how long will it take for all the servos to finish the movement. It doesn't matter if each servo is far or near its final location, SSC32 will calculate and apply the speed for each servo so all them finish at the same time!! 

This is very powerful to create complex movements. And they will be performed smoothly

Lets get down to business.
In my case, I am using the SSC32 to control an arm with 6 servos (more about this in future posts)  and I thought it would be nice to be able to command it from an Arduino.


The only "problem" is that the serial protocol defined by the SSC32 is a bit "uncomfortable" to handle, so I created a class to handle it and make it a bit more comfortable.

You can find the library for Arduino here (decompress it inside the "libraries" folder of your arduino environment):




And here is an example of how to use the library:

#include <SSC32.h>

/*
  Tests the SSC32 library. By Martin Peris (http://www.martinperis.com)
  This example code is in the public domain.
 */

SSC32 myssc = SSC32();

void setup() {


  //Start comunications with the SSC32 device  
  myssc.begin(9600);



}

void loop() {

  //Move motor 0 to position 750
  //The first command should not define any speed or time, is used as initialization by SSC32
  myssc.servoMove(0,750);

  delay(1000);

  //Move motor 1 to position 750
  //The first command should not define any speed or time, is used as initialization by SSC32
  myssc.servoMove(1,750);

  delay(1000);

  //Move motor 0 to position 1500. It will take 5 seconds to finish the movement.
  myssc.servoMoveTime(0,1500,5000);

  delay(5500);

  //Move motor 1 to position 900. It will take 5 seconds to finish the movement
  myssc.servoMoveTime(1,900,5000);

  //Move both servos to position 750 at the same time. 
  //The movement will take 5 seconds to complete
  //Notice that currently motor 0 is at position 1500 and motor 1 is at position 900,
  //but they will reach position 750 at the same time
  myssc.beginGroupCommand(SSC32_CMDGRP_TYPE_SERVO_MOVEMENT);
  myssc.servoMoveTime(1,750,5000);
  myssc.servoMoveTime(5,750,5000);
  myssc.endGroupCommand();

  delay(5500);

}



[EDIT 2011/11/24]: The library has been adapted to the new version of arduino's IDE. Thanks to Marco Schwarz.

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