#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define OLED_RESET     4
#define SCREEN_ADDRESS 0x3C
Adafruit_SSD1306 display(OLED_RESET);

#define PIN_ANTENNA A0
#define CHECK_DELAY 1000
#define lmillis() ((long)millis())

const unsigned char zmaj[] PROGMEM = {
  // Bitmap data for your symbol
  // ...
};

void setup() {
  Serial.begin(9600);
  pinMode(PIN_ANTENNA, INPUT);

  display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS);
  display.clearDisplay();
  display.drawBitmap(0, 0, zmaj, 128, 64, WHITE);
  display.display();
  delay(2000);
  display.clearDisplay();
  display.setTextSize(1.2);  
  display.setTextColor(WHITE);
  display.setCursor(30, 10);  
  display.println("SAR");
  display.setCursor(10, 20);  
  display.println("DETECTOR");
  display.display();
  delay(2000);
}

void showReadings(int emfValue) {
  float adjustedEmfValue;
  if (emfValue < 150)
    adjustedEmfValue = emfValue * 0;
  else
    adjustedEmfValue = emfValue * 1.7;

  display.clearDisplay();
  display.setTextSize(1);  
  display.setTextColor(WHITE);
  display.setCursor(0, 0);  
  display.print("EMF: ");
  display.print(adjustedEmfValue);
  display.print(" MHz");

  float sarValue = adjustedEmfValue * 0.0021;

  display.setCursor(0, 10);  
  display.print("SAR: ");
  display.print(sarValue, 2);  
  display.print(" W/Kg");

  int barWidth = map(emfValue, 0, 1023, 0, 120);
  display.fillRect(4, 20, barWidth, 10, WHITE);

  display.display();
}

void loop() {
  static int avgValue = 0, emfValue = 0;
  static long nextCheck = 0, emfSum = 0, iterations = 0;

  emfValue = constrain(analogRead(PIN_ANTENNA), 0, 1023);
  emfSum += emfValue;
  iterations++;

  if (lmillis() - nextCheck >= 0) {
    avgValue = emfSum / iterations;
    emfSum = 0;
    iterations = 0;
    showReadings(avgValue);
    nextCheck = lmillis() + CHECK_DELAY;
  }
}