September 28, 2010
about 4 years ago
I ordered this for an aerodesign project at Boise State. We have a competition in < 3 weeks.
I have this interfaced to an ATxmega128A1. I can write to it fine, but what I am finding is that it is a bit sensitive. Also, when the PIC gets confused, there is no recovery. Since this is a one way communication, there is no way to tell if the display is messed up or not. I’m finding this to be a pretty severe issue.
When I power up my system, sometimes i get glitches on the LCD screen. Often when I write things to the screen, I get odd results. This is at 9600Baud.. seriously??? I communicate over serial lines at > 400Kbps, this should be a piece of cake.
To be honest, the glitches don’t happen that often, but I am concerned that they happen at all, and that I cannot recover the LCD. I have a command to try and send all of the reset codes to it, but nothing works. Once the PIC goes off into the weeds, I cannot recover it. Is there some sort of reset sequence I can try?
At this point, the LCD is probably “good enough”, but I really dislike a state machine that locks up hard and won’t recover.
FWIW - I am using 3.3V, verified and tested. I do have a wire harness, which is about 2 feet long. I added a cap between ground and the RX line because without that, I was getting terrible noise and lots of errors on the LCD. More garbage than clean characters.
I am sure that there is some coupling of noise from the RX line to the power, but, are there no caps on the board?? Okay, a quick check of the board shows that.. there is a single 0.1uf cap. Wow.. hardly adequate. Maybe I’ll put something heftier on the board for power..
Never mind.. I put some crazy big caps on the power and it does not help. I need a cap between RX and Ground to get the thing to work at all..
Hopefully I’m making some simple mistake, so if anyone can point out what I’m doing wrong - I’ll be grateful.. it’s always possible I got a bad unit.. stuff does happen.
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