slave pin usage:


50-53 = spi to master
0-1 = serial debugging
22-29 = switched capacitance filter (LOW or INPUT)
30-37 = antennas (HI or LOW, four antenna arrays use only 30-33)
A0 = zero crossing detector input






slave needs to receive commands to
0- SYN: skip this byte, do not parse a parameter (sync)
1- REQ: respond to master when requesting zero crossing offset
        response is 1-179 (percentage of clock * 180)
2- CMD: change clock speed
        next byte is speed in hz * 10 ("100" = 1khz)
3- CMD: stop scanning antennas and select specific antenna
        next byte is antenna to select 0-7
        255 = start scanning
4- CMD: select between 4 and 8 antennas
        next byte is 4 or 8
5- CMD: change scan rotation direction?
        next byte is 0 (up) or 1 (down)
6- CMD: select low or high for antenna selection?
        next byte is 0 (LOW) or 1 (HIGH)
7- CMD: set 180 degree phase angle addition
        next byte is 0 or 180

monitor the zero crossing detector and remember clock offset
        (phase angle selction cmd-6 watches for rising or falling edge)
 






display can use a 5 pin xlr
- VCC
- GND
- IN (ws2812)
- OVERLOAD
- LOW SIG