Ladedruck Waveshare 1.28

#include "SPI.h"
#include "Adafruit_GFX.h"
#include "Adafruit_GC9A01A.h"
#define TFT_DC 7
#define TFT_CS 10

// Hardware SPI on Feather or other boards
Adafruit_GC9A01A tft(TFT_CS, TFT_DC);

int boostPressure;
int boostMax = 0;
int boostMax1 = 2500;
int boostMin = 0;
int boostMin1 = 0;
int ypos = 128;


unsigned long startMillis;
unsigned long currentMillis;
const unsigned long period = 100;

const int sensorHistoryLength = 128;
int sensorHistory[sensorHistoryLength];
int sensorHistoryPos = sensorHistoryLength - 1;

#define DISPLAY_BACKLIGHT  A9 // Pin for backlight control (-1 for none)
#define BACKLIGHT    1


void setup() {

//  Serial.begin(9600)
  tft.begin();
  tft.fillScreen(GC9A01A_BLACK);
    startMillis = millis();


}

void loop() {
    currentMillis = millis();
  if (currentMillis - startMillis >= period) {
    readSensorData();

    startMillis = currentMillis;
  }
    tft.setTextColor(GC9A01A_MAGENTA,GC9A01A_BLACK );
    tft.setCursor(240 - ypos, 140);
    tft.setTextSize(3);

    char cstr[6];
    dtostrf((float)boostPressure / 100  , 1, 2, cstr);


    tft.print(cstr);
    tft.setCursor(50, 140);
    tft.print("NOW");
    tft.setCursor(120,80);

    dtostrf((float)boostMax / 100  , 1, 2, cstr);

    tft.print(cstr);
    tft.setCursor(50, 80);
    tft.print("MAX");

}


float normaliseSensorData(int m) {

  return (m - 104) / 0.1638;
}


void readSensorData(void) {
  float absolutePressure = normaliseSensorData(analogRead(A7));

  boostPressure = (absolutePressure - 830) / 14.504 ;


  if (boostPressure > boostMax) boostMax = boostPressure;
  if (boostPressure < boostMin) boostMin = boostPressure;
}