2020-04-23 updates in general

first a-law experiment : https://github.com/kelu124/echomods/blob/master/include/experiments/auto/20200421b.md
worked on comparing both boards: https://github.com/kelu124/echomods/blob/master/include/experiments/auto/20200421a.md – need a full fledge mini before moving forward with the comparison.
verilog alaw compression is ok and simuls on icarus OK too.
Idea for i2s update on rpi : https://github.com/ryankurte/rpi-i2s-stereo/blob/master/instructions.md
@done check newer lit3rick.vF
@done merge bgd/and (acq + i2s + transfo)
@cancelled go onto yosys (not possible from a up5k perspective.. too tight on timings)
@done understand echoes from acqs.. weird things
@done consider additional CS ( https://www.raspberrypi.org/forums/viewtopic.php?t=152014 ) or SPI ( https://www.raspberrypi.org/forums/viewtopic.php?p=821666#p821666 )

Written on April 23, 2020