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Originally Posted by nicozeg
Could that be solved by joining grounds of both PCs?
In fact that happens through the power cable to the wall, but maybe a more direct path can be better.
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Problem there is ground float. The return currents times the wiring resistance means that 'ground' at the little IC board will not be the same as 'ground' at the CPU socket of the target PC. You could try to tie the ground of the two PC together, but you have the risk that some of the current supplied by PSU-A will want to return via PSU-B, and switcher power supplies don't like that.
In my experiments, I used an
optically isolated SMBus. The IC board was powered by the target PC and grounded at the socket, but the control and logging was done on the electrically isolated second PC.
Perhaps our good buddy MMZ_TimeLord could make a small, separate SMBus isolation board?
pH, the Grothometer is pretty much useless until/unless I get an o-scope to calibrate it. And with the ongoing underemployment, that might be a while.