AVR-Chat

hello guys,

i have a system that has 1 master microcontroller that communicates to 
18 slave microcontrollers. I am going to use a USART in UART mode. 
Since the master is using only one UART, there are control lines so 
that the communication b/n slave and master is one at time to avoid 
corruption. My question is that is this method reliable? When one 
slave controller transmit (toggling the lines high and low), hows does 
other slave controller affect the data? will they hold the line high? 
Any idea?

consulted mr google and seems rs485 is one solution. 

rgrds

mgu

----- Original Message ----- 

From: "magzky02" <magzky02@yahoo.com>
To: <AVR-Chat@yahoogroups.com>
Sent: Wednesday, February 28, 2007 7:49 AM
Subject: [AVR-Chat] When boyscouts say one for all, all for one


>
> hello guys,
>
> i have a system that has 1 master microcontroller that communicates to
> 18 slave microcontrollers. I am going to use a USART in UART mode.
> Since the master is using only one UART, there are control lines so
> that the communication b/n slave and master is one at time to avoid
> corruption. My question is that is this method reliable? When one
> slave controller transmit (toggling the lines high and low), hows does
> other slave controller affect the data? will they hold the line high?
> Any idea?
>
> consulted mr google and seems rs485 is one solution.

It was the Three Musketeers!

RS-485 is one way. You could also daisy-chain the slaves and use the UARTs, 
with each slave passing the message onto the next. You will need some sort 
of addressing system; when the correct slave identifies the message, it 
performs the desired action otherwise it passes it on to the next slave.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
leon355@btinternet.com
http://www.geocities.com/leon_heller

I have used RS485 to do this as a master/slave half-duplex system 
with one master and 8 slaves.  RS485 is nice in that all you need to use 
is two IO lines to any unit.  Address arbitration is handled by using 
"9th bit" serial which all USARTs support, and many will interrupt on. 
Check that out for your network.

DLC

magzky02 wrote:
> hello guys,
> 
> i have a system that has 1 master microcontroller that communicates to 
> 18 slave microcontrollers. I am going to use a USART in UART mode. 
> Since the master is using only one UART, there are control lines so 
> that the communication b/n slave and master is one at time to avoid 
> corruption. My question is that is this method reliable? When one 
> slave controller transmit (toggling the lines high and low), hows does 
> other slave controller affect the data? will they hold the line high? 
> Any idea?
> 
> consulted mr google and seems rs485 is one solution. 
> 
> rgrds
> 
> mgu
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 

-- 
---------------------------------------
Dennis Clark    TTT Enterprises
---------------------------------------