Inkplate 4 TEMPERA touchscreen Y coordinate unreliable with normal pressure

TECHNICAL SUPPORT Inkplate
1

Customer:

The X coordinate is correct, but the Y coordinate is always off unless I touch the screen very gently. With normal pressure like operating a phone or e-book reader, it usually reads somewhere between 250-300 Y coordinate regardless of where I tap.

Originally submitted via email support on 17 April 2025. Migrated to the forum for community visibility.

2

Soldered Support:

Are you using the official examples? Does the touchscreen operate incorrectly with the example sketches?

Can you run this example: Inkplate-Arduino-library/examples/Inkplate4TEMPERA/Basic/Inkplate4TEMPERA_Touch_Registers/Inkplate4TEMPERA_Touch_Registers.ino at master · SolderedElectronics/Inkplate-Arduino-library · GitHub

This example will print the contents of the touch registers. Let me know what it says when you attempt to use the touchscreen.

3

Customer:

I received a new sample and unfortunately the touchscreen is still not working correctly.

Here are videos demonstrating the issues:

These basic examples are not functioning properly with a normal touch. Is the device supposed to be controlled with a stylus or other accessory? Or is it a library issue? I don’t understand why the second sample is practically not usable when the touchscreen is the main reason I chose this product.

4

Soldered Support:

We’ve reviewed your videos and determined this is a software issue. The Inkplate 4 TEMPERA has two different variations, and we have not sufficiently tested the touchscreen driver on the version without the glass panel, which appears to be the one you have. Per the manufacturer’s datasheet it should work the same way but there are differences.

We will update the driver and send you a corrected version of the Inkplate library.

5

Soldered Support:

We investigated further and determined the following:

The driver is working as intended and is the same as other Inkplate 4 TEMPERA drivers. We tested the touchscreen and discovered it only really responds well to very light touches and registers the touch where intended towards the release of the touch (when your finger is leaving the surface).

This is a sensitivity issue with the touchscreen. The glass panel version has less sensitivity precisely because of the glass panel surface. We attempted to lower the sensitivity via the driver but this was unsuccessful as the driver is plug and play and just gives the coordinates it receives over i2c. We attempted to implement a workaround by ignoring the first 20 touches and averaging the last 5, but this was unsuccessful as each touch is different and the approach worked inconsistently.

We determined:

  1. The glass panel Inkplate 4 TEMPERA works well over touch; this version is different
  2. Touch works much better if the device runs on battery. Unplug from the PC after uploading your sketch and run the device on battery - touch will work great. Running over USB power causes grounding issues, creating noise in the capacitive touchscreen reading. This is a hardware design flaw for this particular model.
  3. Placing a thin protective film over the panel also greatly improves the sensitivity issues.

These workarounds greatly improve the grounding issue.

Attachment omitted in migration: image.png