634 LCD issues - not working properly


New member
I've just received my CFA634-YMC-KS LCD. I applied +5v to the +5 (lcd) pad and a ground. The lcd booted up with the crystalfontz boot screen. I then applied +5v to the (led) pad and the backlight turned on as well.

after a few tests of this (power up/power down), the backlight comes on, but the crystalfontz boot screen does not any longer, all i get now is an lcd full of '}' characters.

Any ideas on what might be the problem? I have double checked voltage at +5v and ground is secure. :(

Also, I have shorted JPA in preparation of using this via spi
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New member
Ok...i took the short off the JPA and made a 9pin to 9pin cable... ran the Crystalfontz WinTest software and was able to reset the contrast... i'll change it back to spi, and try again.:)


New member
Well...for anyone reading.. I was able to reset the lcd with the CF Boot Screen Beta program by saving to eeprom. apparently something in my spi application is sending faulty information and corrupting the display. I've soldered a switch on JPA to flip it from spi mode to 232. This is great as i'll be able to troubleshoot the spi problem and flip to 232 to reset the lcd if needed :)
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CF Tech

That is possible I guess.

Situations like this are part of the reason we went to packets with CRCs on them in the new products. Much less possible to have "random" errors.

I am glad you have it working.