I'm very much on the software side of things so I'm super inexperienced with debugging hardware. A custom processor I'm working with gives 2 debug pins, and given that it's an ARM system I suspect it to be 2-wire SWD. Looking at some tools I found online, specifically J-Link, it looks like I need to not only connect the two debug pins, but also a ground pin. However, I'm not given a third pin and I don't have a pinout of the processor due to it being a custom build. Is there a way to find a ground on the processor?

  • Software guy here too, I highly recommend using a multimeter to identify ground points (continuity test) and voltages in general. Jun 17 '20 at 1:23

Usually all the grounds on the PCB are connected together, so look for something like a metal shield, USB connector housing, or any other element that should be connected to ground (e.g. a capacitor). There may also be big copper areas used for the ground plane.

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