Serial Input

I am working on a test bench code. I want to display “Enter PSI”… I then do calculations and store the calculated values to compare to the actual reading I am getting. I am running into an issue where I can input my PSI… it will do the calculations and compare to the real value…but it never resets. I can re-enter a value and it shows the new calculated values, but never sends out the pulse to get a new reading. I guess I am having a problem looping the program to restart so I can test another board.

I can tell it is not outputting a new pulse because I am viewing the outputs with my oscilloscope.

Any help is much appreciated. My code is below.

#include <math.h>

double INPUT_PSI;
double V_OUT_CALC;
double V_OUT_CALC_2;
//float HALF = 1/2;
double DAC_READING;
double EXPECTED_ANALOG;
double EXPECTED_ANALOG_PLUS;
double EXPECTED_ANALOG_MINUS;
int ADC_OUT;
boolean VALUE_ENTERED = false;

String readString;
int Signal = 7;

void setup () 
{
  Serial.begin(9600);
  pinMode(Signal, OUTPUT);
  pinMode(A0, INPUT);

Serial.println("Please enter PSI reading");

}

void loop () 
{
 // Serial.println("Please enter PSI reading");
  while (Serial.available())
    {
  //    Serial.println("Please enter PSI reading");
      char p = Serial.read();
      readString += p;
      delay (2);
      
//        if (readString+=p == 'n/')
//          {
//      VALUE_ENTERED = true;
//      continue;
//          }
    }
  
   if (readString.length () >0)
    {

      INPUT_PSI = readString.toInt ();
      V_OUT_CALC = (INPUT_PSI * .02)+.5;

      Serial.println ("V OUT:");
      Serial.println (V_OUT_CALC);
      Serial.println(" "); 
    //  Serial.println(INPUT_PSI);
    
      DAC_READING = (.003 * ((V_OUT_CALC/5)*1023)-.306);
      Serial.println ("DAC_READING:");
      Serial.println (DAC_READING);
      Serial.println(" "); 
      
      EXPECTED_ANALOG = ((DAC_READING+.306)/.003);
      Serial.println("EXPECTED_ANALOG:");
      Serial.println(EXPECTED_ANALOG);
      Serial.println(" "); 
      
      EXPECTED_ANALOG_PLUS = (EXPECTED_ANALOG *1.01);
      Serial.println("EXPECTED_ANALOG_PLUS:");
      Serial.println(EXPECTED_ANALOG_PLUS);
      Serial.println(" "); 
      
      EXPECTED_ANALOG_MINUS = (EXPECTED_ANALOG *.99);
      Serial.println("EXPECTED_ANALOG_MINUS:");
      Serial.println(EXPECTED_ANALOG_MINUS);
      Serial.println(" ");   
      
      delay(200);
      
      digitalWrite(Signal, HIGH);
      delay(20);
       
      ADC_OUT = analogRead(A0);
      Serial.println("ADC_OUT:");
      Serial.println(ADC_OUT);
      Serial.println(" "); 
     
     if (ADC_OUT >= EXPECTED_ANALOG_MINUS && ADC_OUT <= EXPECTED_ANALOG_PLUS)
     {
      Serial.println ("PASS");
     }
    else 
     {
       Serial.println("FAIL");
     }
       
       digitalWrite(Signal, LOW);
      INPUT_PSI = 0;
      V_OUT_CALC = 0;
      readString="";
      DAC_READING = 0;
      EXPECTED_ANALOG = 0;
      EXPECTED_ANALOG_PLUS = 0;
      EXPECTED_ANALOG_MINUS = 0;
      ADC_OUT;
    }
//return;
}

You could use ParseInt : http://arduino.cc/en/Serial/ParseInt

And a NewLine is '\n'.