Touchscreen

XPT2046.js module code:

/*

XPT2046 (pin/function compatible to ADS7843) 
Resistive Touch Screen Controller module

` ` `
var touch, touchModule = require("XPT2046");

function onInit() {
      // ...
      // setup touchscreen 
      SPI2.setup({sck:B13, miso:B14, mosi:B15, baud: 2000000});
      touch = tMod.connect(
          // spi, cs, irq, callback, calc // landscape
          SPI2, B10, B1, function(x, y, rd) {  // portrait
              if (x !== undefined) {
                console.log(x,y);
              }
      }, function(yr, xr, d) { // calc function - converts raw data to x / y coordinates;
        // scale and offset values calculated using markers and default calc function.
        // see http://forum.espruino.com/conversations/­292641 - Touchscreen     
//      return [ Math.round(xr / xsc + xos) // / x scale per pixel + x offset
//             , Math.round(yr / ysc + yos) // / y scale per pixel + y offset
        return [ Math.round(xr / -121.44          + 259.70685111989) 
               , Math.round(yr /   88.90357142857 + -19.78130398103)
               ];
      });
      // ...
}
` ` `

 */

exports = // XPT2046 module
{ calc: function(x, y, d) { return [x,y,d]; } // default calculation
, connect: function(spi, cs, irq, callback, calc) {
    // overwrite default 'calculation': pass thru incl. raw values
    if (calc) { this.calc = calc; }
    // wake the controller up
    spi.send([0x90,0],cs);
    // look for a press
    var watchFunction = function() {
      var interval = setInterval(function () {
        if (!digitalRead(irq)) { // touch down
          var d = spi.send([0x90,0,0xD0,0,0], cs);
          callback.apply(undefined, this.calc(d[1]*256+d[2], d[3]*256+d[4], d));
        } else {
          callback();
          clearInterval(interval);
          interval = undefined;
          setWatch(watchFunction, irq, { repeat : false, edge: "falling" });
        }
      }.bind(this), 50);
    }.bind(this);
    setWatch(watchFunction, irq, { repeat : false, edge: "falling" });
    return this;
  }
};

Application using the (minified) module code from local Web IDE sandbox/modules folder. Note the touchscreen module .connect() that is supplied with the calculation function to converts the raw screen controller data into x and y for the screen.

// TFT24TRCportraitCalibr3.js - XPT2046 module test
//
//  2.4" 240x320 262K Color TFT LCD ILI9341 on SPI1 with 
//  Resistive Touch Screen Controller XPT2046 on SPI2
//  using out of box ILI9341 and ADS7843 modules.
//
// Wiring:
//  2.4"
//  DSP                  PICO [<---USB
//   1   VCC      red     3   3.3            shared
//   2   GND      blk     1   GND            shared
//   3   CS       blu     7   B6   CS        LCD
//   4   RST      brn     9   A8   reset RST LCD
//   5   D/C      grn     8   B7   D/C       LCD
//   6   MOSI     ylw     6   B5   SPI1 MOSI LCD
//   7   SCK      wht     4   B3   SPI1 SCK  LCD
//   8   LED      org    18   A5   LED       LCD
//   9   MISO     grn     5   B4   SPI1 MISO LCD
//  10   T_CLK    wht    23   B13  SPI2 SCK  Touch
//  11   T_CS     ylw    22   B10  CS        Touch
//  12   T_MOSI   grn    25   B15  SPI2 MOSI Touch
//  13   T_MISO   blu    24   B14  SPI2 MISO Touch
//  14   T_IRQ    blk    21   B1   IRQ       Touch

var dW = 240, dH = 320, dsp, dMod = require("ILI9341"),
    touch, tMod = require("XPT2046");

// marker specs (lik dice face 5; top left to bottom right)
var mrks =
    [{i:1, label:"topLeft    ", x: 20, y: 20, xOff: 14, yOff:-6}
    ,{i:2, label:"topRight   ", x:220, y: 20, xOff:-66, yOff:-6}
    ,{i:3, label:"center     ", x:120, y:160, xOff:-29, yOff:14}
    ,{i:4, label:"bottomLeft ", x: 20, y:300, xOff: 14, yOff:-6}
    ,{i:5, label:"bottomRight", x:220, y:300, xOff:-74, yOff:-6}
    ];
var mSiz = 9; // half of marker size, (0.7 of font size)

// print marker at x/y of size s with x/y label
function mrkr(d,x,y,s,xOff,yOff) {
  dsp.setColor(1,1,1);
  dsp.drawRect(x-s,y-s,x+s,y+s);
  dsp.drawLine(x-s,y,x+s,y);
  dsp.drawLine(x,y-s,x,y+s);
  dsp.setFontVector(s / 0.7);
  dsp.drawString(x + " / " + y, x+xOff, y+yOff);
}

function fInt(i,l) { return ("        " + i).substr(-l); }

function onInit() {
  A5.set();
  SPI1.setup({sck:B3, miso:B4, mosi:B5, baud: 1000000});
                   // spi, dc, cs, rst, callback
  dsp = dMod.connect(SPI1, B7, B6, A8, function() {
      dsp.clear();
      // print markers like dice face of 5
      mrks.forEach(function(m) {
        mrkr(dsp, m.x, m.y, mSiz, m.xOff, m.yOff); });
      // setup touchscreen 
      SPI2.setup({sck:B13, miso:B14, mosi:B15, baud: 2000000});
      touch = tMod.connect(
          // spi, cs, irq, callback, calc
          SPI2, B10, B1, function(x, y) {
            if (x !== undefined) {
              console.log(fInt(x,4),fInt(y,4));
            }
          }, function(yr, xr, d) {
            // calc function - converts raw data to x / y coordinates;
            // scale and offset values calculated using calibration 
            // markers and default calc function. For more details see
            // http://forum.espruino.com/conversations/­292641 - Touchscreen
//          return [ Math.round(xr / xsc + xos) // / x scale per pixel + x offset
//                 , Math.round(yr / ysc + yos) // / y scale per pixel + y offset
            return [ Math.round(xr / -121.44          + 259.70685111989) 
                   , Math.round(yr /   88.90357142857 + -19.78130398103)
                   ];
      });
  });
}

onInit();

Related console output (tapping on markers on screen).

NOTE the last 4 lines which lay outside of the display, because the touch screen has a pretty sizable porch at the bottom.

 1v86 Copyright 2016 G.Williams
>echo(0);
=undefined
  21   18
  22   19
  22   18
 223   20
 222   19
 121  162
 118  160
 121  162
  18  303
  19  303
  17  301
 219  303
 219  300
 220  300
 220  302
 130  333
 127  324
 128  328
 126  324
> 

Note: This module is used in Modular and extensible UI framework and ui elements conversation.

1 Attachment

• TFT24TRCportraitCalibr3.js