LCD missing characters - timing problem?

Testing/Troubleshooting
1

Hi everyone.

I ran into a problem with my MB64-to-be: The LCD (a 16x4 Displaytech 164A) seems to randomly ignore half of the characters it should display.

When booting up the Midibox, i first get the 1. and 3. line of the LCD filled with black blocks. After that, it displays something like “MO 16 ()23Tle”,  obviously a garbled version of “MIOS v1.6 © 2003 Th. Klose” or whatever it SHOULD display.

Somehow i have this feeling that the timing between the LCD and the PIC is incorrect, i.e. the PIC sends the characters faster than the LCD can handle them or something like that.

Anyone ever ran into the same problem? Anyone got an idea how to fix this?

2

Normally there can´t be any timing problem. As the PIC sends the code to display (one character) it waits until the LCD says “OK, did it”. I would guess either the LCD got a prob or perhaps some of your solder points are not quite perfect…

Greetz

3

Hmm. I hope the LCD itself isn’t the problem, but i checked all the connections “PIC -> header” and

“socket -> LCD” and the problem doesn’t seem to be in the connections. :frowning:

4

This problem can appear when there is a short between the data and/or control pins

Best Regards, Thorsten.

5

Just measured resistance between all the neighbouring pads on the LCD, never lower than ~ 470 Ohms (measured with the LCD connected to the core).  :-/