Dell Latitude 7350 2-in-1 touchscreen firmware update ghost touch problem

I just applied a Synaptics touchscreen firmware update to a Latitude 7350 2-in-1 ...and it completely hosed the touchscreen. There is now a ghost living inside the touchscreen clicking random things in the upper left quadrant. Here's what I've tried:

0.) Cleaning and recalibrating the touchscreen
1.) Reapplying the firmware update (the same one -- the original firmware is not available as far as I can tell)
2.) Resetting the EC by pulling the main battery
3.) Resetting the CMOS by pulling all batteries
4.) Flashing many previous revisions of BIOS
5.) Tweaking power management settings for both the I2C device and the whole machine
6.) Booting a Linux live image -- the same thing happens, so it's not a driver problem

This machine is well out of warranty so I'm on my own. I've noticed that it is less extreme on AC power, but it still happens.

The touchscreen model is a Synaptics 7501 Clearpad and seems to be found in the Acer Switch 12 as well. It identifies as SYNA7501. Unfortunately I can't find any firmware files for the Acer.

Here's the firmware update from Dell:
https://www.dell.com/support/home/e...ode=wt64a&productcode=latitude-13-7350-laptop

Does anyone here have any contact at Dell that could get me the original stock Synaptics touchscreen firmware for the Latitude 7350?

 

Might risk this one:
Dell Venue 11 Pro 7130 and 7139 Sharp / Samsung Touch Panel Firmware Patch

It uses the same Synaptics update utility and two of the extracted binaries claim 's7501' + 'DS5 R3.0.0' in their header whereas the one from your update has 's7501' + 'DS5 R3.1.1'.

If that doesn't work then there's always the possibility to disconnect its cable for the interim. That is, if it won't allow you to disable the device separately from the display.

Last resort is borrowing or purchasing a display from one of the supported systems and copy the firmware from there:
Dell Venue 11 Pro 7139 Flawed LCD Touch Screen Panel FH4F5 FHD 2168 Tested

Asking price is $16, but with all the scratches the seller might take up on some haggling.

 

Thanks for the digging! Interesting, the images won't apply as-is, but maybe if I spend some time comparing them side by side in a hex editor I can make some sense out of it. The config file for the updater lets you specify the image and product identifiers so I may have some luck if go that route.

To make the system actually usable I just disabled the HID touchscreen device in Windoze device manager.

In the meantime, I realized that the digitizer board is about $5 on ebay, so I ordered one of those. Fingers crossed that it solves the issue.

 

The digitizer board replacement fixed the problem. It was a pretty easy installation, but the ribbon cables are pretty small. Unfortunate that I had to replace actual hardware to undo a bad firmware upgrade. It would be much better if Dell provided the original firmware files for its devices.