#include "Adafruit_GFX.h"
#include "Adafruit_ILI9341.h"

#define TFT_DC 9
#define TFT_CS 10
#define TFT_RST 8
#define TFT_MISO 12
#define TFT_MOSI 11
#define TFT_CLK 13

Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_MOSI, TFT_CLK, TFT_RST, TFT_MISO);


int analogInput = 0;
float vout = 0.0;
float vin = 0.0;
float R1 = 100300.0; // resistance of R1 (100K) -see text!
float R2 = 9880.0; // resistance of R2 (10K) - see text!
int value = 0;

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

tft.begin();
tft.fillScreen(ILI9341_BLACK);
tft.drawRect(0, 0, 120, 160 , ILI9341_GREEN);
tft.drawRect(120, 0, 240, 160 , ILI9341_GREEN);

tft.drawRect(0, 160, 120, 320 , ILI9341_GREEN);
tft.drawRect(120, 160, 240, 320 , ILI9341_GREEN);

pinMode(analogInput, INPUT);

void setRotation(uint8_t rotation);
}

void loop() {

   // read the value at analog input
   value = analogRead(analogInput);
   vout = (value * 4.770) / 1024.0; // see text
   vin = vout / (R2/(R1+R2));
   if (vin<0.09) {
   vin=0.0;//statement to quash undesired reading !
}

////////////////////////// 1° QUADRANTE /////////////////////////////

tft.setCursor(2,51);
tft.setTextColor(ILI9341_YELLOW);
tft.setTextSize(1);
tft.setRotation(3);
tft.println("TENSIONE:");

tft.setCursor(50,45 );
tft.setTextColor(ILI9341_WHITE);
tft.setTextSize(2);
tft.setRotation(3);
tft.println(vin);

////////////////////////// 2° QUADRANTE /////////////////////////////

tft.setCursor(163,51);
tft.setTextColor(ILI9341_YELLOW);
tft.setTextSize(1);
tft.setRotation(3);
tft.println("TENSIONE:");

tft.setCursor(211,45 );
tft.setTextColor(ILI9341_WHITE);
tft.setTextSize(2);
tft.setRotation(3);
tft.println(vin);

////////////////////////// 3° QUADRANTE /////////////////////////////

tft.setCursor(2,171);
tft.setTextColor(ILI9341_YELLOW);
tft.setTextSize(1);
tft.setRotation(3);
tft.println("TENSIONE:");

tft.setCursor(50,165 );
tft.setTextColor(ILI9341_WHITE);
tft.setTextSize(2);
tft.setRotation(3);
tft.println(vin);

////////////////////////// 4° QUADRANTE /////////////////////////////

tft.setCursor(163,171);
tft.setTextColor(ILI9341_YELLOW);
tft.setTextSize(1);
tft.setRotation(3);
tft.println("TENSIONE:");

tft.setCursor(211,165 );
tft.setTextColor(ILI9341_WHITE);
tft.setTextSize(2);
tft.setRotation(3);
tft.println(vin);

delay(500);
}