Last updated on May 14, 2008
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Upon arriving home from work today I found a white box in the mail from Scotland indicating that the new LCD for Ivan’s P3 had arrived. This is the replacement that Colin (the Sequentix guy) offered to people as a replacement for PLEDs which had failed. After eating a bit of dinner I set to installing it.
Because of the spacing of the LCD and function switch board I had to file away a bit of the PCB in order to make it fit nicely. Thankfully Sequentix’s page on the replacement LCDs had mentioned this, so I was expecting to do it.
All in all, it went well. After getting the LCD working I installed the v4 firmware and MemX board, getting the machine wholly up to date.
I’m running into a bit of weirdness with the LCD, though. As can be seen on this page of photos, the display seems to be cutting off some characters during boot, corrupting others, and occasionally causing weirdness. I’ve tried making a new cable and replacing the IC directly connected to the LCD, but that hasn’t been successful. I’m really afraid that the controller on the LCD may be messed up. Hopefully tomorrow I’ll be able to use one of Ivan’s spare LCDs which he was sent (by way of me) by Crystalfontz as replacements for his failed PLEDs.
UPDATE: I just emailed Colin, the Sequentix guy, and asked for suggestions. After talking with a few people I’m starting to feel certain that the problem may simply be that the LCD doesn’t start up fast enough for the P3. It seems that with the HD44780 protocol the LCD talks the user can set up custom characters in the CGRAM (character generator RAM). While I may be way off base, I’m thinking that the P3 sets up the special characters it needs on boot, then tries to display stuff. I think that if the LCD isn’t running stable yet then these characters, along with data written to the display controller itself, could become corrupt or lost, displaying the symptoms like what I’m seeing. Hopefully I’ll find out for sure soon. If this is the problem then a fix would simply require the P3 to wait for another 250ms (or so) at power-on.