https://www.tinkercad.com/things/2aw9sNwB9P9-
Circuit design SPI Master Slave - Tinkercad
Circuit design SPI Master Slave created by Warbling Educator Reindeer 1529 with Tinkercad
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https://lkml.org/lkml/2016/3/30/459
LKML: Mark Brown: Re: [PATCH v4 2/2] spi: spi-pic32: Add PIC32 SPI master driver
mark brown