#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <OneWire.h>
#include <DallasTemperature.h>

#define OLED_WIDTH 128 // OLED display width,  in pixels
#define OLED_HEIGHT 64 // OLED display height, in pixels

#define SENSOR_PIN 5  // The Arduino Nano pin connected to DS18B20 sensor's DQ pin

Adafruit_SSD1306 oled(OLED_WIDTH, OLED_HEIGHT, &Wire, -1); // create SSD1306 display object connected to I2C
OneWire oneWire(SENSOR_PIN);         // setup a oneWire instance
DallasTemperature DS18B20(&oneWire); // pass oneWire to DallasTemperature library

String temperature1_str, temperature2_str, temperature3_str, temperature4_str;

void setup() {
  Serial.begin(9600);

  // initialize OLED display with address 0x3C for 128x64
  if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    while (true);
  }

  delay(2000);         // wait for initializing
  oled.clearDisplay(); // clear display

  oled.setTextSize(2);          // text size
  oled.setTextColor(WHITE);     // text color
  oled.setCursor(0, 10);        // position to display

  DS18B20.begin();     // initialize the sensor
  temperature1_str.reserve(10); // to avoid fragmenting memory when using String
  temperature2_str.reserve(10);
  temperature3_str.reserve(10);
  temperature4_str.reserve(10);
}

void loop() {
  DS18B20.requestTemperatures();             // send the command to get temperatures

  float temperature1_C = DS18B20.getTempCByIndex(0);  // read temperature in Celsius
  float temperature2_C = DS18B20.getTempCByIndex(1);
  float temperature3_C = DS18B20.getTempCByIndex(2);
  float temperature4_C = DS18B20.getTempCByIndex(3);

  temperature1_str  = String(temperature1_C, 2); // two decimal places
  temperature2_str  = String(temperature2_C, 2);
  temperature3_str  = String(temperature3_C, 2);
  temperature4_str  = String(temperature4_C, 2);

  Serial.println(temperature1_str);
  Serial.println(temperature2_str);
  Serial.println(temperature3_str);
  Serial.println(temperature4_str); // print the temperature in Celsius to Serial Monitor

  oled.clearDisplay(); // clear the display once
  oled_display_center("T1:"+ temperature1_str, 0);
  oled_display_center("T2:"+ temperature2_str, 16);
  oled_display_center("T3:"+ temperature3_str, 32);
  oled_display_center("T4:"+ temperature4_str, 48);
  oled.display(); // display all at once
}

void oled_display_center(String text, int yOffset) {
  int16_t x1, y1;
  uint16_t width, height;

  oled.getTextBounds(text, 0, 0, &x1, &y1, &width, &height);

  oled.setCursor((OLED_WIDTH - width) / 2, yOffset); // position text horizontally centered and vertically at yOffset
  oled.println(text);
}