const int SensorPin = 32; // assign SensorPin to pin 32
int Value = 0; // sets initial value of variable "Value" to zero
float Offset = 1.35; // sets value of "Offset" to 1.35

unsigned long previousPrintTime = 0; // declare variable "previousPrintTime"
const unsigned long printInterval = 1000; // 1000 milliseconds or 1 second
bool print = false; // set to false until printing is needed

unsigned long startTime = 0; // declare variable "startTime"
unsigned long elapsedTime = 0; // declare variable "elapsedTime"

int pHValueCount = 0; // declare variable "pHValueCount"
float totalpHValue = 0.0; // declare variable "totalpHValue"

float overallMinValue = 1000; // declare variable "overallMinValue"
float overallMaxValue = -1000; // declare variable "overallMaxValue"

void setup() {
  Serial.begin(115200); // serial communication with baud rate of 115200 bits per sec
  pinMode(SensorPin,INPUT); // sets sensor pin as input
  delay(1000); // delay code for 1 sec
}

void loop() {

  Value = analogRead(SensorPin); // read analog voltage from sensor pin and set value to variable "Value"
    delay(1000); // delay code for 1 sec
    
  if (Serial.available() > 0){ // Lecture 18: if data input into serial port
    char message = Serial.read(); // read what is input and store in variable "message"
    
    if (message == 'p'){ // if message input into serial port is "p"
      print = true; // boolean variable set to true 
      startTime = millis(); // start the timer 
      pHValueCount = 0; // reset pH value count to zero every time p is entered
      totalpHValue = 0.0; // reset total pH to zero every time p is entered
      overallMinValue = 1000; // reset min to 1000
      overallMaxValue = -1000; // reset max to -1000
    }
    if (message == 's'){ // if message input into serial port is "s"
      float averagedpHValue = totalpHValue / pHValueCount; // avg all the pH values
          
      Serial.println("Summary");
          
      Serial.print("Overall average pH value: ");
      Serial.println(averagedpHValue, 2); // print avg pH value to 2 decimal places

      Serial.print("Overall minimum pH value: ");
      Serial.println(overallMinValue, 2); // print min pH to 2 decimal places
          
      Serial.print("Overall maximum pH value: ");
      Serial.println(overallMaxValue, 2); // print max pH to 2 decimal places
      }
  }
  if (print){ // if print is true (which it is set to)
    unsigned long currentMillis = millis(); // returns time passed since code started
      if (currentMillis - previousPrintTime >= printInterval){ // if difference between total time and prev time is >= 1000
          float phValue=(float)Value*3.3/4096/6; //convert the analog into millivolt 
          phValue=3.5*phValue+Offset; //convert the millivolt into pH value 

          totalpHValue += phValue; // adds pH value to totalpHvalue to sum all the values
          pHValueCount++; // add 1 to pHvaluecount which sums number of data points taken

          if (phValue < overallMinValue){ // if the value is less than 1000, it becomes new min
            overallMinValue = phValue; // minimum value is updated
          }
          if (phValue > overallMaxValue){ // if value is more than -1000, it becomes new max
            overallMaxValue = phValue; // max value updated
          }
          Serial.print(" pH:");
          Serial.print(phValue,2); // print pH value to 2 decimal points
          Serial.println(" "); // add space (make it easier to read)
          
          previousPrintTime = currentMillis; // set previous print time to current millis
      }
      elapsedTime = currentMillis - startTime; // time since values started being recorded
}
}