Jonathan Herbst
Isolation
The Grapple Probe has isolation between USB and the DEBUG and COM ports in the capacity that the USB ground and DEBUG/COM port ground can be voltage biased up to 400V RMS continuously without damaging anything on the Grapple Probe. Isolation is implemented on the USB side with an ADUM3160 to isolate the USB signals and a transformer with a transformer driver to isolate power. These devices can handle up to 2500 V bias, but only for a limited amount of time, 1 minute.
Isolation is kind of a niche requirement, but it is important for this project because I was inspired to make this after damaging some components in another project I was working on due to a ground loop. The project included controlling a 24V stepper motor while powering the controller from the same 24V voltage rail. It had reverse polarity protection so I had my guard down about getting the polarity right when plugging in the power supply, but I had a debug probe connected and when the polarity was reversed the ground through the debug probe was connected directly to the 24V rail. I ended up breaking a bunch of things, including the debug probe, and started thinking about what a debug probe that didn't propagate that mistake would look like.
Theo Heng
electronicsworkshops
Brian Cornell
Nick Sayer