I have some circuit boards laid out and the prototype works. The logic board is an ATMega328 with support chips, driving a 24x16 LED matrix with 3 TLC5916s controlling the columns and 2 74ac138s controlling the rows via MOSFETs.
The LED rows are switched at 50 Khz (for 32 levels of PWM) and I don't observe any problems with wireless mice, WiFi devices, cell phones, or FM radios near the unit, but I can definitely hear interference on an AM radio if it's less than 1 foot away.
I've been reading and it looks like I can reduce interference by adding a ground plane or pour. I can't get a ground pour working on either the top or bottom of the board; no matter what I do the autorouter just complains that the polygon fell apart. I can get it to work by making a separate plane, but that would make the design a lot more expensive because I'd have to go to 4 layer boards.
I do have a free pin on the 2x3 headers that connect the logic board to each LED board (currently 3 go to the 3 columns, 2 go to 2 rows, and 1 is unused). Would connecting the unused pin to ground and adding a ground pour to the the LED boards help?
Or is this even something I need to worry about? I would like to eventually sell these...
Thanks as always!