I am, in a project currently on the board, going to use up to 5 RS485 slaves. These slaves are characterized not by 'slave number' but by 'slave type' (may be >255). Only one slave of any type can exist. The plan is for the master at initialization to sequentially go thorough addresses 8-63 and when getting a response detecting if a conflict exist (two different slave types at thge same address) and if not assign that slave a number 0-7. This process will be repeated till no slave respond to the sequential ping. For this I need the slaves to have random numbers for this period.

sequence:
global address : go random
global address : hold your random number
scan specific addresses as above
repeat till no response to scan

I happen to use Cygnal for this purely digital and do thus have unused A/D, D/A and comparators.

All slaves start at the same time, run at the same clock and thus rand() would not be a good idea.

Can anyone suggest a dirt cheap noise source that produce enough to feed a Cygnal analog input.

Did anyone ever see hat came out od a Cygnal A/D with an open input (the very cheapest)

In advance, thanx

Erik