AVR-Chat

At 04:54 PM 1/10/04 -0400, you wrote:
>Thanks for the reply. Right now I am stuck with 481 on the board, but it 
>seems like it will meet my requirements. I've been reading some more 
>about this throughout the day and it seems that having to bias the bus 
>(using a pullup and pulldown) configuration is quite commonly done.
>

I use 2x560R to bias the line, one to the Vcc and one to ground.
(A+ goes to Vcc and B- goes to ground, just one of this biasing network
is required). Also a 120R in parallel with the comms line at the beginning 
of the line and one at the end of the line. With this set up an lowish baud 
rates you can go up to 1.2Km (4000ft). National Semiconductors has/had
some good info on "10 ways to bullet proof RS485" or something like it.


Regards

John Samperi

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