serial comm problem

[Ioannis]

And if I may add to Melanies post, use if possible optocouplers to drive external power devices. It is the most secure method of isolation.

I had to go twice on a town up in the mountains 250Km away, for an automation once I made with 16C55 and assembly lanquage, but with no isolation and finally understood that I was too inexperienced that time in industrial automation design (long time ago, I would say...).

Ioannis

[mister_e]

AND depending the design, having different ground is also a good practice. It's amazing sometime how a simple looking thing could ruin an entire design.

Probably even worst when you mix, analog, digital and power signal on the same design... oh my god! How many hours i, and many other i guess, already lost to know why... even a bad ground plane design may ruine your life... ARGGGHH!

Thanks to Bead & friends to exist