Arduino — Blog — Casey Bloomquist

When I started playing with Leap control of the Arduino, the first thing I tried was servo control. I was using an example of computer control of a servo that I found online, but was having a lot of difficulty getting the Leap/Processing communication to effectively control it. So, I went back to basics and did some simpler projects with LEDs first. This helped me get comfortable with the Leap - Processing - Arduino system, especially the programming in Processing.

Now I'm back for round II. Not surprisingly, it fell into place pretty easily. Here's the video:

The movement is a little jerky but that is due to the delay I set to give the servo time to move. The one slightly tricky issue I had to deal with was the out of window constraints. It is not shown in the video, but Processing draws a 720 x 720 window on the computer and displays the finger positions as dots. I was using the vertical finger position to control the servo and wanted the servo to go to its min/max position when the finger position was above/below the window. At first I put this constraint in the Arduino code, but there was a problem with negative values getting read as positive values, so I ended up putting it in the Processing code, which ended up being much simpler.

I also set the window to a height of 720 so that I could simply divide the finger height by 4 to map it to the 0-180 range of the servo rather than using the map() function. A more robust implementation would be setup to handle any window size and map accordingly.

The Processing code:

/* Servo Control - hand/finger position controls servo motor angle.
By Casey Bloomquist
Using the OnFormative LeapMotionP5 library (http://www.onformative.com/lab/leapmotionp5/)
*/

import com.onformative.leap.LeapMotionP5;
import com.leapmotion.leap.Finger;
LeapMotionP5 leap;

int angle;

import processing.serial.*;
Serial port;

public void setup() {
  // set window, P3D = 3D rendering
  size(720, 720, P3D); 
  noFill();
  stroke(255);
  
  // set LEAP object
  leap = new LeapMotionP5(this); 
  
  // set com port. Currently: "/dev/tty.usbmodemfd121"
  println("Available serial ports:");
  println(Serial.list());
  port = new Serial(this, "/dev/tty.usbmodemfd121", 9600); 
 }

public void draw() {
  background(0);
  fill(255);
  for (Finger f : leap.getFingerList()) {
    PVector position = leap.getTip(f);
    //PVector velocity = leap.getVelocity(f);
    ellipse(position.x, position.y, 10, 10);
    if (position.y > 720) {
      angle = 180;
    } else if (position.y < 0) {
      angle = 0;
    } else {
      angle = int((position.y) / 4);
    }
    port.write(angle);
    println(angle);
  }
} 

public void stop() {
  leap.stop();
 }  
 

And the Arduino code:

#include <Servo.h>
Servo myServo;

//int handPos;
//int angle;

void setup() {
  myServo.attach(9);
  Serial.begin(9600);
  myServo.write(0);
}

void loop() {
  byte angle;
  
  if (Serial.available()) {
    // Read angle from Processing
    angle = Serial.read();
    Serial.println(angle);
    // If fingers in window, read servo angle
    myServo.write(angle);
    delay(15);
  }
}

// How Many Fingers Am I Holding Up?

import com.onformative.leap.LeapMotionP5;
import com.leapmotion.leap.Finger;
LeapMotionP5 leap;

import processing.serial.*;
Serial port;

public void setup() {
// set window, P3D = 3D rendering
size(600, 600, P3D);
noFill();
stroke(255);

// set LEAP object
leap = new LeapMotionP5(this);

// set com port. Currently: "/dev/tty.usbmodemfd121"
println("Available serial ports:");
println(Serial.list());
port = new Serial(this, "/dev/tty.usbmodemfd121", 9600);
}

public void draw() {
background(0);
fill(255);
int numFingers = leap.getFingerList().size();
print("Number of Fingers: ");
println(numFingers);
port.write(numFingers);
for (Finger f : leap.getFingerList()) {
PVector position = leap.getTip(f);
PVector velocity = leap.getVelocity(f);
ellipse(position.x, position.y, 10, 10);
}
}

public void stop() {
leap.stop();
}

/* How Many Fingers Am I Holding Up?

LEDs attached to digital pin 3-7.
Serial Connection to Processing
*/

void setup(){
// initialize serial communication:
Serial.begin(9600);
// set LED pins 3-7 as outputs
for(int x = 3; x<8; x++){
pinMode(x, OUTPUT);
}
}

void loop(){
byte numFingers;
// check if data has been sent from the computer:
if (Serial.available()) {
// read the most recent byte (which will be from 0 to 255):
numFingers = Serial.read();
if (numFingers == 0){
digitalWrite(3, LOW);
digitalWrite(4, LOW);
digitalWrite(5, LOW);
digitalWrite(6, LOW);
digitalWrite(7, LOW);
} else if (numFingers == 1){
digitalWrite(3, HIGH);
digitalWrite(4, LOW);
digitalWrite(5, LOW);
digitalWrite(6, LOW);
digitalWrite(7, LOW);
} else if (numFingers == 2){
digitalWrite(3, HIGH);
digitalWrite(4, HIGH);
digitalWrite(5, LOW);
digitalWrite(6, LOW);
digitalWrite(7, LOW);
} else if (numFingers == 3){
digitalWrite(3, HIGH);
digitalWrite(4, HIGH);
digitalWrite(5, HIGH);
digitalWrite(6, LOW);
digitalWrite(7, LOW);
} else if (numFingers == 4){
digitalWrite(3, HIGH);
digitalWrite(4, HIGH);
digitalWrite(5, HIGH);
digitalWrite(6, HIGH);
digitalWrite(7, LOW);
} else if (numFingers == 5){
digitalWrite(3, HIGH);
digitalWrite(4, HIGH);
digitalWrite(5, HIGH);
digitalWrite(6, HIGH);
digitalWrite(7, HIGH);
}
}
}