GPi demultiplexing experiment notes

Earlier I paired each RPi with 1 GPi, because I worried that I could not repeated the results due to poor contact wiring, too long cable interferences, intermittantly failing RPi's and or GPi's.  But later I found that perhaps one of the main reasons that I could not repeat an experiment is that I seemed to have corrupted the RPi's internal clock generation logic by trying Guzunty and Wiring Pi's service calls without realizing that they might have set some critical timing registers, and furthermore, I don't know how to reset Wiring Pi's clock frequency setting.

So I think if I don't mess with GPi's and RPi's clock service calls,  I could almost always repeat the experiments.

And since the 1 RPi 1 GPi pairing arrangement is not flexible for mixing and matching, or swapping trouble shooting, or demultiplexing experiments, I decided to pull the GPi board away from the RPi's, and group them far away, for experiments more decoupled from the RPi's.

Now the pair of GPi's each have its own power, LED, and JTAG/SPI/CLK cabling.   Each GPi has been tested OK.  Next step is to do manual demultiplexing, before doing online demultiplexing.

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