[sdiy] Dirty Ground & Bypassing

[Antti Huovilainen]

Hi

Building my midi2cv unit (own design: PIC, 16450 UART, Maxim 14bit DAC),
I've found out the importance of proper grounding. At the moment I've got
about 2mV ground spikes whenever bus access happens but I think I can get
rid of them by adding a latch for DAC address, cs & wr pins.
However, my analog ground has about 1mV very high frequency noise (some
MHZs) that seems to come from the PIC & uart themselves (this noise is
there even when they do nothing at all).
How can this be as I use separate ground for digital & analog boards (two
separate protoboards) and star grounding? 
Pic, dac digital & analog grounds only meet at a single point, but the
noise is on the analog ground. The distance between the star grounding
point and dac analog ground is about 15cm and the noise appears between
these points. 
Could it be because I'm bypassing the dac & voltage reference supply pins
to analog ground? If so, where should I bypass them?

Antti

"If you don't eat yer meat, you can't have any pudding!
 How can you have any pudding if you don't eat yer meat!?"
   - Roger Waters