okay
the doppler has a SAMD and an ice40
It has a C++ library on the SAMD side, which it's not clear to me if it's bespoke, which presents an "ICEClass" object for interacting with the ice40. It has a `ice40.sendSPI16(value);` function, and I need to (but haven't yet done this) search through Doppler's forest of githubs to find the source for ICEClass because it doesn't seem to be documented, but it surely also has a recvSPI16() and hopefully also a send/recvSPI8().
I am making a proof-of-concept to convince myself I can make things with the doppler. I have an FPGA program (linked above) that on its own irregular schedule redraws a 16x16 led grid; I want to transmit the top four bits of that grid, on that irregular schedule, when it changes, to the SAMD so it can play audio to the DAC (which, to my knowledge)
I have previously committed Serial Crimes in firmware and think I am probably qualified to read and implement the SPI spec, but haven't done so yet. Skimming the wikipedia page for SPI it looks like one device is the clock master and I don't know which one it is in the case of the Doppler.