#include <math.h>

int ledPin=13;
int potPin=A0;

void setup()
{
  Serial.begin(38400);
  pinMode(potPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop()
{
  int potPin=A0;
  int potVal1=analogRead(potPin);
  delay(640);
  int potVal2=analogRead(potPin);

  int rSpeed=potVal2-potVal1;

  Serial.print("Velocity over last 690ms: ");
  Serial.println(rSpeed);
  Serial.print("Current Pot Position: ");
  Serial.println(potVal2);

  isIncreasing(potVal1, potVal2, ledPin);
}

  void isIncreasing(int potVal1, int potVal2, int ledPin)
  {
    if (potVal2<potVal1)
    {
      boolean isIncreasing=true;
      digitalWrite(ledPin, HIGH);
    }
    else
    {
      boolean isIncreasing=false;
      digitalWrite(ledPin, LOW);
    }
  }