HDMI 7" 800x480 Display Backpack - With Touchscreen issues

[dI_ce]

TL:DR - after un-and re-plugging the device the display stopped being recognized properly. The EDID changed due to unknown reasons.

Hi all,

I am using the display together with an Intel NUC 11 board NUC11TNBv5 running Win10. The NUC has two HDMI ports, one has a regular 1080p monitor connected, the other one the 7" touch screen. I was playing around with unplugging and plugging in the cables when suddenly, the 7" screen stopped working properly: the resolution was changed to 640 x 480 pixels (it now has a black border on the right side) and for whatever reason, the display now only works on this specific HDMI port of the NUC. It is not recognized on the other HDMI port, my laptop (Win 10), nor on a Macbook Pro. I tried a new display backpack, thinking that it's an issue with the specific device and the same thing happened again.

The ports all work normally, I tested it with the 1080p monitors and different HDMI cables. The backpack is always powered via a micro-USB cable connected to a USB port on the PC. I checked the drivers and they are all up to date.

I found other threads of similar issues and the suggested fix was always to edit the EDID on the EEPROM of the backpack using an Arduino. Unfortunately, I do not have one. This article https://learn.adafruit.com/adafruit-tfp ... g-the-edid mentions a way to do it on a computer but does not elaborate on it.

Though I still check the EDID of the monitors and the attached picture shows what I found.

EDID.png (91.82 KiB) Viewed 295 times

The upper one is from a fresh 7" Display Backpack connected to my laptop and the lower one is the "broken" display connected to the NUC, since the NUC is the only PC that can still recognize the display. The information has been pulled using Monitor Asset Manager by EnTech Taiwan. I think it simply reads it from the Windows registry.

Does anyone have an explanation of why this could be happening? And a way to edit the EDID without an Arduino?

I appreciate any input!

Cheers

[adafruit_support_carter]

I was playing around with unplugging and plugging in the cables when suddenly

Can you elaborate on what you were doing here. In general, this should not affect the EDID.

[dI_ce]

Can you elaborate on what you were doing here. In general, this should not affect the EDID.

Thank you for your reply.
The NUC has two HDMI ports - I wanted to see if/how the numbering of the monitors in Win10 is affected by which port the monitor is plugged into and/or if it mattered, in which order the monitors are connected. First I had the 7" display plugged into port A, then the 1080p display plugged into port B: works fine. I unplugged the 7" display to plug it back into the same port so see if now the 1080p display would be changed into the main display and the 7" turned into the secondary. At this point the issue already arose.

I could try to replicate this again using another working 7" display that I have here but I am reluctant to possibly break another one without a way of resetting or fixing it.

I appreciate your help!

[adafruit_support_carter]

That seems fine. Not sure why or how that could have changed the EDID written into the EEPROM.

Info on reprogramming is here:
https://learn.adafruit.com/adafruit-tfp ... g-the-edid

You can reprogram the EDID using an Arduino or (possibly) a computer using the HDMI/DVI port if you have software to write the EDID that way.

The EEPROM I2C lines are connected to the HDMI connector. So this is referring to using those. But that's all the information we have about that approach. In general, you will need something that can communicate over I2C to be able to reprogram the EDID stored in the EEPROM.

[dI_ce]

Thank you for the info.

I couldn't find a good way to edit the EDID on Windows so I installed Ubuntu and used i2c-tools instead. That worked well and I could fix the EDID of the 7" display.

It turns out that every time I plug in the display into the specific HDMI port on the NUC, the data at 0x31 of the EDID would be changed from 0x01 to 0x00. This happened both on Windows and on Ubuntu.
The exact cause I still don't know. I also contacted Intel support, maybe they can figure something out.

[adafruit_support_carter]

If you get any good info on what could be causing that, please post it here. Good job reprogramming the EDID! Glad at least that worked.