Rocket Altimeter

//V1   -BMP280 has an accuracy of +-3'.  The initial value is of no concern as the overall Altitude is determine by subtracting the MIN reading from the MAX reading. 
#include "U8glib.h"  //Find and Install this library
#include "BMP280.h"  //Find and Install this library
#include "Wire.h"  //Find and Install this library
#define P0 1013.25 //1021.97  //1013.25  //1028.86 //Height above sea level?  https://whatismyelevation.com/  I really need help with this
BMP280 bmp;

int piezoPin = 9;  //PIN 9 connected to BUZZERs POSITIVE PIN
int waiter = 0;  //Timers Initial State
int result;
int resulta;
int resultb;

U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_NO_ACK);  // OLED DISPLAY Type

char sT[20];
char sP[9];
char sA[9];
char sA_MIN[9];
char sA_MAX[9];
char sA_result[9];
char sA_resulta[9];
char sA_resultb[9];
double A_MIN = 0;
double A_MAX = 0;

void draw2(double T, double P, double A, double A_MIN, double A_MAX, double resulta) {
  u8g.setFont(u8g_font_unifont);

resulta = A_MAX - A_MIN;  //Determine difference in feet between the BMP's MIN and MAX readings
float resultb = resulta / 3.281;  //Result is in METERS

   dtostrf(A_MIN, 4, 2, sA_MIN);
   dtostrf(A_MAX, 4, 2, sA_MAX);
   dtostrf(resulta, 4, 4, sA_resulta);
   dtostrf(resultb, 4, 4, sA_resultb);
  dtostrf(T, 4, 2, sT);
  dtostrf(P, 4, 2, sP);
  dtostrf(A, 4, 2, sA);

  u8g.drawStr( 5, 10 , "Feet : ");
  u8g.drawStr( 60, 10, sA_resulta);

  u8g.drawStr( 5, 30 , "m : ");
  u8g.drawStr( 60, 30, sA_resultb);

  u8g.drawStr( 5, 45 , "TEMP : ");
  u8g.drawStr( 60, 45, sT);
 
  u8g.drawStr( 5, 62, sA_MAX);
  u8g.drawStr( 60, 62, sA_MIN);
  
}

void setup() {

 pinMode(2, OUTPUT);  //Set PIN 2 as an OUTPUT for the RED LED
 pinMode(3, OUTPUT);  //Set PIN 3 as an OUTPUT for the BLUE LED
 pinMode(4, OUTPUT);  //Set PIN 4 as an OUTPUT for the Green LED
  Serial.begin(9600);
  if (!bmp.begin()) {
    Serial.println("BMP init failed!");
    while (1);
  }
  else Serial.println("BMP init success!");

  bmp.setOversampling(4);

  u8g.setColorIndex(1);
  u8g.setFont(u8g_font_unifont);
}


void loop(void) {

int redl = 2;  //Name Pin 2 redl
int white = 3; //Name PIN 3 white
int redr = 4; //Name Pin 4 redr

int wait = 50;  //delay in ms, 1000ms equals one second
int wait2 = 30;  // delay in ms, 1000ms equals one second
int wait3 = 10;  // delay in ms, 1000ms equals one second

waiter = waiter + 1;  //Increases the VALUE of WAITER by ONE every PROGRAM CYCLE
if (waiter >= 600) tone(piezoPin, 2000, 50);  // Set Buzzer Delay based on # of program cycles.  Sets Buzzers frequency and how long it beeps for

digitalWrite(redl, HIGH); // turn the redl LED ON
delay(wait2); // PAUSE
digitalWrite(redl, LOW); // turn the redl LED OFF
delay(wait); // PAUSE

digitalWrite(white, HIGH); // turn the white LED ON
delay(wait2); // PAUSE
digitalWrite(white, LOW); // turn the white LED OFF
delay(wait); //PAUSE

digitalWrite(redr, HIGH); // turn the redr LED ON
delay(wait2); // PAUSE
digitalWrite(redr, LOW); // turn the redr LED OFF
delay(wait); //PAUSE

  double T, P;
  char result = bmp.startMeasurment();

  if (result != 0) {
    delay(result);
    result = bmp.getTemperatureAndPressure(T, P);

    if (result != 0) {
      double A = bmp.altitude(P, P0);

      if ( A > A_MAX) {
        A_MAX = A;
      }

      if ( A < A_MIN || A_MIN == 0) {
        A_MIN = A;
      }

      do {
        draw2(T, P, A, A_MIN, A_MAX, resulta);    //(A_MIN, A_MAX, resulta);  //Tells the program to go to DRAW2
      } while ( u8g.nextPage() );
      u8g.firstPage();
      delay(wait3);
     
    }
    else {
      Serial.println("Error.");
    }
  }
  else {
    Serial.println("Error.");
  }

  delay(wait3);

}