XPT2046 (ADC for touch screen) Z-axis pressure measurement (resistance)

Other Hardware Sensors
1

I added a routine (based on the X / Y reading made by the Utouch library) to calculate the Z axis, but the XPT2046 datasheet is very confusing, I would like a second opinion on the XPT2046 configuration that I need to set the value correct to calculate the resistance Z.

 touch_WriteData(0xB4);
  pulse_high(P_CLK, B_CLK);
  TP_Z1 = touch_ReadData();

  touch_WriteData(0xC4);
  pulse_high(P_CLK, B_CLK);
  TP_Z2 = touch_ReadData();

To read the value Z1 I set the value 0xB4,

0xB4 in binary is 1 011 0 1 00:

  • B7: start bit
  • B6-4: channel selection bit = Z1- position
  • B3: 12-bit mode
  • B2: Simple connection
  • B1-0: power down mode

To read the value Z2 I set the value 0xC4,

0xB4 in binary is 1 100 0 1 00:

  • B7: start bit
  • B6-4: channel selection bit = Z2- position
  • B3: 12-bit mode
  • B2: Simple connection
  • B1-0: power down mode

But in some codes that I found on the internet, the setting value is not always the same, some codes use different values (from the value I used: 0xB4 / 0xC4).

Although the value I got is very comfortable, but I need to confirm if it is the correct value, my touch plate results in a value close to 500 for the Z axis when touched by a pen.

Note: the Utouch library is obsolete, and has been replaced by the URtouch library, it is not free for commercial use:

/*
URTouch.h - Arduino/chipKit library support for Color TFT LCD Touch screens
Copyright (C)2016 Rinky-Dink Electronics, Henning Karlsen. All right reserved

Basic functionality of this library are based on the demo-code provided by
ITead studio.

You can find the latest version of the library at
http://www.RinkyDinkElectronics.com/

This library is free software; you can redistribute it and/or
modify it under the terms of the CC BY-NC-SA 3.0 license.
Please see the included documents for further information.

Commercial use of this library requires you to buy a license that
will allow commercial use. This includes using the library,
modified or not, as a tool to sell products.

The license applies to all part of the library including the
examples and tools supplied with the library.
*/

XPT2046.zip (1.94 KB)