An Epic Tale Of Reset Line Detective Work

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The Pine64 folks have given us so many tasty pieces of hardware over the last few years, but itā€™s fair to say that their products are for experimenters rather than consumers and can thus be a little rough around the edges at times. Their Clusterboard for example is a Mini-ITX PCB which takes up to seven of their SOPINE A64 compute modules, and networks them for use as a cluster by means of an onboard Gigabit Ethernet switch. Itā€™s a veritable powerhouse, but it has an annoying bug in that it appears reluctant to restart when told. [Eric Draken] embarked upon a quest to fix this problem, and while he got there in the end his progress makes for a long and engrossing read.

We journey through the guts of the board and along the way discover a lot about how reset signals are generated. The eventual culprit is a back-EMF generated through the reset distribution logic itself causing the low-pulled line to never quite descend into logic 0 territory once it has been pulled high, and the solution an extremely simple application of a diode. For anyone who wishes to learn about logic level detective work itā€™s well worth a look. Meanwhile the board itself with its 28 ARM cores appears to have plenty of potential. Itā€™s even a board weā€™ve mentioned before, in a personal supercomputer project.



from Blog ā€“ Hackaday https://ift.tt/3fijVrj

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