LCD tearing / desync

[Squishymonster]

I picked up a 3.5" TFT LCD from Adafruit that takes RCA as input. My Uzebox which works on typical CRTs exhibits slow tearing or desync with Tetris - but at any given time, the image is roughly 90% correct. I haven't compared against any other video sources yet.

If I verify that other sources tend to work properly, what options might I have for removing the desync? I am okay with modifying the firmware and breaking compatibility - this is more a learning exercise.

I noticed that the LCD control board crystal is slightly different from the Uzebox - I don't recall exactly but it's within maybe 1.5mhz. I wondered if they run at slightly different times. But I don't understand yet how a CRT would handle that better than an LCD controller.

[Squishymonster]

I did find this discussion regarding 524 vs 525 video lines:

https://forums.adafruit.com/viewtopic.php?f=39&t=10344

[Squishymonster]

Okay, I have found a good bit of information on this. My previous search attempts weren't hitting on the magic words. Searching these forums for "524 525" has provided some good information. If there have been any discoveries since then, feel free to throw some more info at me

[uze6666]

The Uzebox implements the very exact same timing as the progressive scanning used on the NES, Genesis and SNES, that's is, it was 524 lines and not 525 (no half lines in there). So I believe if you plugged that screen in a NES, it would yield the same problem. It's been quite some time since I played with the sync code. But, unfortunately, implementing half line sync could be complicated. That probably doesn't help much, but the simplest route would be to find a screen that support 524 progressive mode!

There's quite a lot of those "rear car monitor" screen that works fine and can be found on Aliexpress for much cheaper than Adafruit.