gripper.js

var Board = require("../lib/board.js"),
    Servo = require("../lib/servo.js"),
    __ = require("../lib/fn.js");

/**
 * Gripper
 *
 * Supports:
 *   [Parallax Boe-Bot gripper](http://www.parallax.com/Portals/0/Downloads/docs/prod/acc/GripperManual-v3.0.pdf)
 *
 *   [DFRobot LG-NS](http://www.dfrobot.com/index.php?route=product/product&filter_name=gripper&product_id=628#.UCvGymNST_k)
 *
 *
 * @param {[type]} servo [description]
 */
function Gripper( opts ) {

  if ( !(this instanceof Gripper) ) {
    return new Gripper( opts );
  }

  // Default options mode, assume only when opts is a pin number
  if ( typeof opts === "number" ) {
    opts = {
      servo: {
        pin: opts,
        range: [ 0, 180 ]
      },
      scale: [ 0, 10 ]
    };
  }

  // Default set() args to 0-10
  this.scale = opts.scale || [ 0, 10 ];

  // Setup servo
  // Allows pre-constructed servo or creating new servo.
  // Defaults for new Servo creation fall back to Servo defaults
  this.servo = opts.servo instanceof Servo ?
    opts.servo : new Servo( opts.servo );
}

[
  /**
   * open Open the gripper
   *
   * @return {Object} this
   */
  {
    name: "open",
    args: function() {
      return this.servo.range[0];
    }
  },
  /**
   * close Close the gripper
   *
   * @return {Object} this
   */
  {
    name: "close",
    args: function() {
      return this.servo.range[1];
    }
  },
  /**
   * set Set the gripper's open width
   *
   * @param  {Number} 0-10, 0 is closed, 10 is open
   *
   * @return {Object} this
   */
  {
    name: "set",
    args: function( position ) {
      // Map/Scale position value to a value within
      // the servo's lo/hi range
      return Math.floor(
        __.map(
          position,
          this.scale[0], this.scale[1],
          this.servo.range[1], this.servo.range[0]
        )
      );
    }
  }
].forEach(function( api ) {
  Gripper.prototype[ api.name ] = function() {
    return this.servo.move(
      api.args.apply( this, [].slice.call(arguments) )
    );
  };
});

module.exports = Gripper;