bypass capacitors

If you need such large capacitors then I think you fixed the symptom, not the cause. The 10uF caps you installed are not bypass caps but 'temporary batteries'.

This actual cause is most likely a case of mixing signal ground with power ground, using power traces that are too thin, or an insufficient power supply. I'm sure you were taught to separate high-power sections of the design from low-level signal sections?

Rob

Hehe, you're right. I posted way to soon. Damn optimism. Problem was incorrect port setup on the MCU turning on a latch for a brief moment when it shouldn't have been. The latch enables various circuits, and the current rush must have been too much for the lcd. Hence the 'temporary battery' that fixed the problem.

At uni we were taught nothing about circuit layout in digital systems. Everything was just 1's and 0's, no mention of the analogue side, race conditions, ground bounce, etc. I've stumbled upon all the problems by chance, and thanks to this newsgroup solved all of them. :)

Ross.

One of Don Vonada's engineering maxims:

Digital circuits are made of analog parts.

Lesson 1.

Just my EUR .02.

There is no such thing as a purely digital circuit. Electromagnetic Compliance testing proves this daily.

On the bypassing question, there was a long thread not so long ago. Although rules of thumb are useful, they remain that, not solid rules that may always be used.

I have parts that require both bulk and high frequency bypass. The short answer is 'check the datasheet'

Cheers

PeteS

.....and more importantly these days they operate as though they were little RF transmitters and receivers. Therefore, some RF theory would go a long way in helping you to lay out PCB's so that they stood a chance of behaving properly.

Look at the di/dt rates for all your circuits and ensure that the transmission line (which is what the PCB tracks tend to be) impedance is configured to be low enough at the appropriate frequencies.