blimp code

blimpo.cc

/* 
  borrowed:
  - IR code/library from http://www.arcfn.com/2009/08/multi-protocol-infrared-remote-library.html
  - ultrasonic sensor code from http://arduino.cc/en/Tutorial/Ping
*/

#include <IRremote.h>
#include <Servo.h> 

// pins pins pins
const int IR_SENSOR = 2; // bow && stern?
const int PORT_MOTOR = 3;
const int STARBOARD_MOTOR = 5;
const int THRUSTER_SERVO = 6;
const int ULTRASONIC_SENSOR = 9;

// apple remote buttons
const int PLAY = 2011275421;
const int VOLUMEUP = 2011254941;
const int VOLUMEDOWN = 2011246749;
const int PREVIOUS = 2011271325;
const int NEXT = 2011259037;
const int MENU = 2011283613;

// some othe variables the blimp needs
const float e = 2.7182818284590452354;
IRrecv ir_reciever(IR_SENSOR);
decode_results ir_results;
Servo servo;
long altitude = 0;
long ideal_altitude = 120; // in cm
int altitude_change_threshold = 100;
int thruster_position = 90; // 180 total degrees
int port_motor_speed = 0; // 0-255, though it seems the motors don't really start until around ~50
int starboard_motor_speed = 0; // 0-255


void setup(){
  Serial.begin(9600);
  ir_reciever.enableIRIn();
  servo.attach(THRUSTER_SERVO);  
  servo.write(90);
  pinMode(PORT_MOTOR, OUTPUT);
  pinMode(STARBOARD_MOTOR, OUTPUT);
}

void loop(){
  //handle_ir_input();
  update_thruster();
  update_motors_speed();
  delay(100);
}

void handle_ir_input(){
  if (ir_reciever.decode(&ir_results)) {
    switch(ir_results.value){
      case PLAY:        break;
      case MENU:        break;
      case VOLUMEUP:    break;
      case VOLUMEDOWN:  break;
      case NEXT:        break;
      case PREVIOUS:    break;
      default:          break;
    }  
    ir_reciever.resume(); 
  }  
}

long current_altitude(){
    pinMode(ULTRASONIC_SENSOR, OUTPUT);
    digitalWrite(ULTRASONIC_SENSOR, LOW);
    delayMicroseconds(2);
    digitalWrite(ULTRASONIC_SENSOR, HIGH);
    delayMicroseconds(5);
    digitalWrite(ULTRASONIC_SENSOR, LOW);
    
    pinMode(ULTRASONIC_SENSOR, INPUT);    
    long duration = pulseIn(ULTRASONIC_SENSOR, HIGH);
    long new_altitude = microsecondsToCentimeters(duration);
    // sometimes it seems the sensor gives a bogus reading, i think this should cancel it out
    //return abs(altitude - new_altitude) > altitude_change_threshold || new_altitude == 0 ? altitude : new_altitude;
    return new_altitude;
}

long microsecondsToCentimeters(long microseconds){
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}

void update_motors_speed(){
  analogWrite(STARBOARD_MOTOR, starboard_motor_speed);
  analogWrite(PORT_MOTOR, port_motor_speed);  
}

void update_thruster(){
  long altitude = current_altitude();
  if(altitude == 0) return;
  
  signed long diff = ideal_altitude - altitude;
  if(diff > 0 && diff > 90) diff = 90;
  if(diff < 0 && diff < -90) diff = -90;
  
  int angle = (int) (90 + diff); 
  servo.write(angle);  
  
  Serial.print("altitude is ");
  Serial.print(altitude);
  Serial.print(" and angle is ");
  Serial.print(angle);
  Serial.println();  
}