I am thinking of first connecting PC to the first board thru Tx/RX, the
    first board to the second board thru Tx/Rx, the second board to the
    third board, and so on. So the system looks like daisy chain
    configuration. Since I am going to control each board one by one, I may
    have to assign an ID for each of them. So when I want to control the
    20th board, since the PC is connected to the first one, the program
    checks until it finds #20 board and sets the register.

You mean like this?


+->Rx.PC1.Tx---->Rx.PC2.Tx--->Rx.PC3.Tx--->Rx.PC4.TX---...-->Rx.PC36.Tx--+
|                                                                        |
|                                                                        V
+------------<--------------------<-------------------<------------------+

Congratulations!  You've reinvented the ring network.  I did that too, back
in college, and am still (again?) thinking of using it for some extendable
controller setups I'm working on (ok, a sprinkler controller.)  I don't see
anything wrong with a scheme like this (and it has a bunch of advantages),
but it's beginning to bother me that I've never seen it used anywhere.

I supposed that it would be worthwhile to read up on the history of token
ring networks (like - why do they need a token in the first place?) to see
why all the complexity got added to such a simple idea, but I've never
gotten around to it...

BillW

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