Quick experiment to demonstrate touch screen debouncing/smoothing

touchdebounce.ino

/*
 * Quick experiment to demonstrate touch screen debouncing/smoothing
 */

#include <Elegoo_GFX.h>    // Core graphics library
#include <Elegoo_TFTLCD.h> // Hardware-specific library
#include <TouchScreen.h>

#define YP A3  // must be an analog pin, use "An" notation!
#define XM A2  // must be an analog pin, use "An" notation!
#define YM 9   // can be a digital pin
#define XP 8   // can be a digital pin

//Touch For New ILI9341 TP
#define TS_MINX 120
#define TS_MAXX 900

#define TS_MINY 70
#define TS_MAXY 920

// For better pressure precision, we need to know the resistance
// between X+ and X- Use any multimeter to read it
// For the one we're using, its 300 ohms across the X plate
TouchScreen ts = TouchScreen(XP, YP, XM, YM, 300);

#define LCD_CS A3
#define LCD_CD A2
#define LCD_WR A1
#define LCD_RD A0
// optional
#define LCD_RESET A4

// Assign human-readable names to some common 16-bit color values:
#define  BLACK   0x0000
#define BLUE    0x001F
#define RED     0xF800
#define GREEN   0x07E0
#define CYAN    0x07FF
#define MAGENTA 0xF81F
#define YELLOW  0xFFE0
#define WHITE   0xFFFF

Elegoo_TFTLCD tft(LCD_CS, LCD_CD, LCD_WR, LCD_RD, LCD_RESET);

int x = 0, y = 0, z = 0, trace_x = 0;

void draw_text( uint16_t color )
{
  tft.setCursor( 10, 10 );
  tft.setTextSize( 1 );
  tft.setTextColor( color );  
  tft.print( String( x ) + ", " + String( y ) + ", " + String( z ) );
}

void draw_cursor(TSPoint p)
{  
  tft.drawPixel(p.y, p.x, BLUE);
}

struct ExpFilter
{
  float k;
  int x_old;
  ExpFilter(float _k) { k = _k; x_old = 0; }

  void reset() { x_old = 0; }
  int filter(float x)
  {
    x_old = k * x + (1.0 - k) * x_old;
    return x_old;
  }
  
};

ExpFilter f(0.1);

int scale_z( int z )
{
  return map(z, 0, 500, tft.height() - 10, 10);
}

void draw_trace(TSPoint p)
{ 
  tft.drawFastVLine(trace_x, 0, tft.height(), BLACK);
  tft.drawFastVLine(trace_x + 1, 0, tft.height(), WHITE);

  tft.drawPixel(trace_x, scale_z( p.z ), BLUE);
  tft.drawPixel(trace_x, scale_z( f.filter( p.z ) ), GREEN );
    
  trace_x++;
  if( trace_x >= tft.width() ) trace_x = 0;   
}



void setup() {
  // put your setup code here, to run once:
  tft.reset();
  tft.begin( 0x9341 );
  tft.setRotation( 1 );
  tft.fillScreen(BLACK);
  pinMode(13, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:

  digitalWrite(13, HIGH);
  TSPoint p = ts.getPoint();
  digitalWrite(13, LOW);

  // if sharing pins, you'll need to fix the directions of the touchscreen pins
  pinMode(XM, OUTPUT);
  pinMode(YP, OUTPUT);

  p.x = map(p.x, TS_MINX, TS_MAXX, tft.height(), 0);
  p.y = map(p.y, TS_MINY, TS_MAXY, tft.width(),  0);

  draw_trace( p );
//  draw_text( BLACK );
//  x = p.x; y = p.y; z = p.z;
//  draw_text( BLUE );

  //delay(20);
}