Hacking FMark LCD display

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[this thread split from David Prentice's original thread about TFT-SPI displays]

John_A_Brown wrote:
I may have mentioned this before, but I haven't yet found a cheap TFT module that brings the VSync line out to the connector. This is a bit of a pain if you want to have tear-free screen re-writes. In fact even a register bit that could be polled would probably be good enough.

John, I did a lot of searching and investigating.

All the 37 pin modules you find on ebay have pin 21 marked as N/C.

Pin 21 seems to be a general purpose pin that gets used for different purposes in OEM applications.

Because sometimes it is an input and sometimes an output when they get sold after-market they leave this pin open.

I found that the 2.8" ILI9325 sold by the ebay seller "coldtears" has a 0402 sized resistor unpopulated on the FPCB.

When I traced the copper leading to the IC DIE and matched up the other pins with the data sheet it looked like it lead to FMark (the frame flyback output).

Long story short. Populated R6, programmer the ILI9325 to output FMark and I was in luck.

There may be a lot more of them on ebay that have the FMark output. I only bought tried two and the one from "coldtears" was a success. The other looked like it went to IFx to set the unit in 6800 mode.

With FMark I have a pretty flash little AVR games system.

With some fancy AVR tricks I can clear pixels at 8M Pixels/S and draw lines/sprites at between 0.2 and 1M pixel/S. All synced to the frame flyback for flicker free awesome.

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Many thanks. I have just ordered one to play with.

John

Four legs good, two legs bad, three legs stable.

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John,

Here is a photo of the back of the FPCB.

R3 is the jumper for FMark.

If you can see any other on ebay that look like that on the back they should be good. Though most don't show a photo of the back.

Attachment(s): 

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Andrew, what value resistor did you use?

John

Four legs good, two legs bad, three legs stable.

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about 1K but thats just 'cause what I had on hand.

0 ohm would be fine if you know you are not going to accidentally try to drive it.

We can start a new thread rather than hijacking if you want to know anything else I have found about FMark.

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andrewm1973 wrote:
about 1K but thats just 'cause what I had on hand.

0 ohm would be fine if you know you are not going to accidentally try to drive it.

We can start a new thread rather than hijacking if you want to know anything else I have found about FMark.


Yes, I thought about it just after I'd posted, and realized that I could add a resistor on my PCB.
That way I'd be able to link the R3 pads(I don't keep 0402 resistors as a rule).
Agreed about a separate thread, good idea.
Maybe one of the gods, sorry mods could split this one?

John

Four legs good, two legs bad, three legs stable.

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Hmmph.
My display was delivered today:
http://www.ebay.co.uk/itm/121033831967?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2648
Sadly, it seems to be slightly different. No R3 to be found.
The only unpopulated component on either side is labelled D2.
Oh,and the listing included a PCB adapter that wasn't sent, but that's another story.

John

Four legs good, two legs bad, three legs stable.

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I now have two of the displays with the unpopulated R3, but no time to play!
I will get back to this later.

John

Four legs good, two legs bad, three legs stable.