pid_test.ino

/********************************************************
 * PID Basic Example
 * Reading analog input 0 to control analog PWM output 3
 ********************************************************/

#include <PID_v1.h>

#define PIN_INPUT 0
#define PIN_OUTPUT 3

//Define Variables we'll be connecting to
double Setpoint, Input, Output;

// TODO Really not sure what these tuning parameters should be? :(
/*
Kp: Determines how aggressively the PID reacts to the current amount of error (Proportional) (double >=0)
Ki: Determines how aggressively the PID reacts to error over time (Integral) (double>=0)
Kd: Determines how aggressively the PID reacts to the change in error (Derivative) (double>=0)
*/
//Specify the links and initial tuning parameters
//double Kp=2, Ki=5, Kd=1;
double Kp=1, Ki=0.1, Kd=1;
PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT);

void setup()
{
  Serial.begin(115200);

  //initialize the variables we're linked to
//  Input = analogRead(PIN_INPUT);

  // Needs to be set initially
  //  Option 1. Use current heading where boat is pointing
  //  Option 2. Calculate bearing between where boat is and next way point
  Setpoint = 45;

  //turn the PID on
  myPID.SetMode(AUTOMATIC);

}

void loop()
{
//  Input = analogRead(PIN_INPUT);

  // Get current boat heading
  Input = 0;
  myPID.Compute();

  Serial.print("Output: ");
  Serial.println(Output, 2);

  // Use Output to set rudder position
  // Will need smoothing! Look at http://forum.arduino.cc/index.php?topic=336130.msg2317322#msg2317322

//  analogWrite(PIN_OUTPUT, Output);

  delay(2000);
}