/*
  Arduino | coding-help
  Screen Flicker when updating values
  Syn [puffy], puffy - Tuesday, May 5, 2026 5:26 PM
  Trying to make a custom digital boost/vacuum gauge with a map sensor.
  I finally got the values to be stable but it's causing my SPI screen to
  flicker.
*/

#include <Adafruit_GFX.h>
#include <Adafruit_ST7789.h>
#include <SPI.h>

#define TFT_CS     10
#define TFT_RST    9
#define TFT_DC     8
#define TFT_BLK    7  // Backlight pin
#define ST77XX_VFD_BLUE 0x0f7e  // this is a "565 RGB" value

const double VREF = 5.00;
const int SENSOR_PIN = A0;
const int MODE_SW_PIN = 2;

double oldValue = 99.0; // always different on boot

Adafruit_ST7789 tft = Adafruit_ST7789(TFT_CS, TFT_DC, TFT_RST);

float psiToInHg(float value)  {
  float convertedValue = value * 2.036;
  return convertedValue;
}

void setup() {

  Serial.begin(115200);
  Serial.println("ST7789 Display Test");

  pinMode(MODE_SW_PIN, INPUT_PULLUP);
  pinMode(TFT_BLK, OUTPUT);
  analogWrite(TFT_BLK, 255);  // Set backlight to full brightness (0-255)

  tft.init(240, 320);
  tft.setRotation(3);  // Adjust rotation if needed
  tft.fillScreen(ST77XX_BLACK);
  tft.setTextSize(3);
  tft.setCursor(10, 10);
  //tft.setTextColor(ST77XX_BLUE, ST77XX_BLACK);
  tft.setTextColor(ST77XX_VFD_BLUE, ST77XX_BLACK);
}

void loop(void) {
  char buffer[16];
  char pressBuff[8];
  float displayPressure = 0.0;

  bool isPSI = !digitalRead(MODE_SW_PIN);

  int rawValue = analogRead(SENSOR_PIN);  // read the input pin
  int mappedValue = map(rawValue, 0, 1023, -30, 20);
  float voltage = (rawValue * VREF) / 1023.0;
  float pressure = (5.8149 * voltage) - 14.211;
  //float pressure = (voltage - 14.183) / 5.8083;

  //int rawADC = analogRead(A0);
  //float voltage = float(rawADC) / 1024.0 * 5.0;
  //float pressure = (voltage - 0.5) / 4.0 * 15.0;

  if (!isPSI) {
    displayPressure = psiToInHg(pressure);
  } else {
    displayPressure = pressure;
  }

  if (displayPressure != oldValue) {
    oldValue = displayPressure;
    Serial.print("Raw value: ");
    Serial.println(rawValue);   // print raw sensor reading
    Serial.print("Voltage: ");
    Serial.println(voltage);   // print raw sensor reading
    Serial.print("PSI: ");
    Serial.println(pressure, 2);   // print raw sensor reading
    Serial.println();

    // puts the float pressure into a char array, pressBuff
    dtostrf(displayPressure, 6, 2, pressBuff);

    snprintf(buffer, 16, "%s %s ", pressBuff, isPSI ? "PSI" : "inHg");
    tft.setCursor(40, 50);
    tft.print(buffer);
  }
}