Very weird LCD problem...

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Joined: 31/12/2012
Location: New Zealand
Posts: 9139
Posted: 03:17am 18 Apr 2024      

I've now checked the LCD sockets - just pulled up and off the plastic insulator thing, leaving just the pins soldered in the board.  No shorting going on in there, everything looks fine.  Put the plastic insulator thing-y's back on.

I then used my multimeter(on diode-test, which only allows a forward current of about 1mA or so) to test all the pins.  NOTHING is shorted out between pins, none of the SPI lines are shorted to ground or supply or each-other.

Everything is PERFECT.....but it won't work in this PCB, which as far as the LCD setup is concerned, is exactly the same as the old board.  Put the MM2 and the exact same LCD module back in the old board - the LCD works just fine.

I really don't understand this, and I was actually hoping to find a shorted pin(or pins) on either the LCD socket or the IC socket.

I also tested with both the LCD and the MM2 chip OUT of the board, so I could rule out any kind of parasitic thing perhaps spoiling the results - no error found.

If it WAS just a touchy LCD module, you'd expect another LCD to work then, woulden't you, but nope.  

ANd it's not like this is my first LCD - I've lost track of how many of the SPI LCD modules I have used in various things, so......brain overload....