int analogPin = 0;
int raw = 0;
int Vin = 5;
float Vout = 0;
float R1 = 0;
float R2 = 1000;
float buffer = 0;

const float R1_min = 0.0;
const float R1_max = 100.0;
const float bar_min = 0.0;
const float bar_max = 7.0;
const float bar_per_ohm = (bar_max - bar_min) / (R1_max - R1_min);

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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 32
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

void setup() {
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.clearDisplay();
  Serial.begin(9600);
}

void loop() {
  raw = analogRead(analogPin);
  if (raw) {
    buffer = raw * Vin;
    Vout = buffer / 1024.0;
    buffer = Vin / Vout - 1;
    R1 = R2 * buffer;
    float bar = (R1 - R1_min) * bar_per_ohm;
    Serial.print("Vout: ");
    Serial.println(Vout);
    Serial.print("R1: ");
    Serial.println(R1);
    Serial.print("Bar: ");
    Serial.println(bar);
    display.clearDisplay();
    display.setCursor(0, 0);
    display.setTextSize(1);
    display.setTextColor(WHITE);
    display.print("OIL PRESS bar: ");
    display.print(bar, 1);
    display.display();
    delay(1000);
  }
}