connected USB to CR while having DUT ground connected with the laptop ground

[rufsiany_sr]

I have been using CR successfully for almost 2 years and have been very careful not to create ground loops. However, in the end, as a result of a moment of inattention, it happened as I described in the title.
CR survived (partially): it still measures the current and displays it on the OLED screen.
However, connecting a USB to it to record the current reading freezes the display and touch panels.
(as always, (except this one time) the DUT is battery powered with no other connections to the outside world)

I understand this is a rhetorical question, but is there anything easy to replace to restore USB functionality?

[Felix]

Typically the MCU might survive in most cases but the USB peripheral might be damaged.
So the answer is ... MCU swap. Depending where you are - I can do it for you if you are willing to return it and pay a small fee to cover the MCU and return shipping.
I always just use a USB isolator, it's a very good investment especially if you play around with a ton of different boards or questionable origins and you perhaps risk a very expensive desktop computer.

[rufsiany_sr]

...........I can do it for you if you are willing to return it and pay a small fee to cover the MCU and return shipping.
It's very nice of you. Thank you very much. I live in Poland, but (what a coincidence!) I'll be in Los Alamos, NM in September. I'll be there for 3 weeks, so if I can get by without USB data logging by then, I'll take the CR with me and send it to you for repair. (For further communication, I will use the "Contact" form under the "About" tab on your website.)
Two suggestions on CR functionality (which anyway is a great and indispensable tool in my repository) that would be very useful. At least for me:
1. Latching the maximum value and displaying on the screen. Cleared on restart. (Maybe it's because since I lost the USB, I focused on the information displayed on the screen
2. Any statistics about the signal: mean, variance? Reset on restart?
(Point 2 is of course much more complicated and only nice to have, so maybe just p. 1?)
Best Regards

[Felix]

Sure just reach out to felix at lowpowerlab .com anytime when you get on this side.
Similar suggestions have been made. I was too busy (and lazy?) to implement something. The source code is available so I thought anyone can contribute if they are so excited about a feature and so inclined to have it sooner than I can do it :-)
I of course still want to improve the CR in that and other ways. Just no time for non critical stuff right now.
I am working on a much much bigger project that has taken my prime energy for the last 2 years.

[Felix]

As a conclusion to this thread:
The CR in question was cleaned and inspected and found no issue. All measurements are within spec and the OLED, USB and other core functions all work normally.