I'll try and work out a metal can or shield for the breakout board, as well as digging out some ceramic discs.
Okay, I added some ceramics on the power pins (of the FT232RL board, not the chip itself), and put a bead onto the VCCIO line, and looped the motor wires a few times around another bead.
It merely fails more often with that setup.
![smile smile](/images/graemlins/default_dark/smile.gif)
Oh well. Still worth trying. Some series resistance in te CBUS lines might help. The issue is that you're still not 100% certain "where" it's getting in exactly.
Is that with the 1000uF still in place?
Isn't the point of breadboarding to work out the bugs *before* you go to PCB?
To some extent yes, but when you're having EMI/EMC issues, using breadboard/veroboard you can't always fix things. It does let you "play" with solutions much easier though.
Things like radiated/conducted emissions can be greatly affected merely by PCB layout. Short (and long) tracks can make massive differences. And immunity is often closely related to emissions.