AVR-Chat

mago Umandam wrote:
>  
>   Ohhh... thanks you for your advice... ;)
>    
>   regards
>    
>   mago
>   
> 
> Andreas Stemmer <groovingandi@gmx.de> wrote:
>           magzky02 wrote:
>> I am using a micocontroller to communicate with 18 other 
>> microcontrollers via rs489. Using the IC MAX3088, and a 100 ohm 
>> resistor across A and B.. Since there are 19 MAX3088, there are also 
>> 19 100 ohm in parallel. IS there something wrong with this?
> 
> Yes, for a RS485 bus, you usually have one 120 ohm termination resistor
> on each end, not on each transceiver. You should also think about
> biasing the bus lines in order to have a defined state when no
> transmitter is active.
> 
> Look at some of the available RS485 application notes.
> 
> AS

Circuit cellar have a good rs485 doc by Bob Perrin
http://www.circuitcellar.com/library/ccofeature/perrin0799/c79bp3.htm

Just using rs485 myself for a bridge(steel) vibration monitoring system.
The painful part is making sure I have proper lightning protection  , 
proper galvanic isolation and grounding.

Alex