design.txt

things that exist on the device:
	adcs
	dacs?
	gpios
	pwms

messages to send:
	request data from gpio
	request data from adc
	request continual transfer from adc

desiderata:
	limited resending so we don't need to do it in app code



HDLC:
	tiny is secondary station
	som is primary station

using sequence and ack numbers, we can get reliability
(seq, ack)

HOST: send (0,0).h, CLIENT: send (0,0).c
HOST: send (1,1).h, CLIENT: send (1,1).c
continue like so

now suppose we have an error
HOST: send (0,0).h, CLIENT: send (0,0).c, client message fails chksum
HOST: send (1,0).h, CLIENT: send (1,1).c
now client sees it has a problem and sends
HOST: send (2,0).h, CLIENT: send (0,2).c, this time it passes chksum
HOST: send (3,1).h, CLIENT: send (1,3).c, back to sync

these ack/send numbers do not need to be large, can use 4 bits each and put them in a byte. This also means we can easily bound the number of elements in a holding array