I am trying to make this board that will enable to to program multiple similar chips with just a push of a button. To do this, I just hook up my MKII programmer and fanout the signals and control which IC gets the clock with a multiplexer. It worked when I did it with 2 Arduinos. However, I made the board and it seems to only program half the time (there are about 18 programmable chips on a board). The error is usually that there is a communication error. I am figuring that maybe when I go past 4, I start getting power consumption issues or maybe it is a signal integrity thing. Any thoughts?

 

Current limitations, speed, length of wiring, parasitic capacitance...
High frequency stuff can get very picky.

 

I am trying to make this board that will enable to to program multiple similar chips with just a push of a button. To do this, I just hook up my MKII programmer and fanout the signals and control which IC gets the clock with a multiplexer. It worked when I did it with 2 Arduinos. However, I made the board and it seems to only program half the time (there are about 18 programmable chips on a board). The error is usually that there is a communication error. I am figuring that maybe when I go past 4, I start getting power consumption issues or maybe it is a signal integrity thing. Any thoughts?

current draw and fan-out are the likely issues. As #12 said, the stray capacitance that makes nice digital signals look like weak sine waves can also be an issue with bigger boards.