Sun Aug 12 14:36:17 EDT 2018

Synchronous SPI

Previously, I've used async SPI.  Since speed is not really a big
problem, it might be easier to use synchronous SPI.  It makes it
easier to test inside Seq.

Just curious: googleing for SPI FPGA what do we get?  Sync or async?

I guess the reason is that it is easier to have a serial signal cross
clock domains.  What I did before was a hack.