Data Transferrinf Over a 25 Meter Wire.

[Shahriar]

Hi
I am designing a new Language laboratory System.
I want to send serial data via a Common bus to all Stations (Students devices).
The length of this bus is around 20-25 meters. Which method is the best
for transferring Data. I mean FSK, RJ485 (if I wrote it right), SPI (that I don't think it work) or ...
The Baude Rate is Around 9600 bps

ThanX in advance
Shahriar

[Tony_Stoynov]

Hi,
if this is only one way connection, you can use the RS232 with a current loop, or RS422. If you whant a real multi node network, then RS485. If you want something a bit hi-tech you can use a low speed optics, HP has a this type of trancivers, actually this is the agilent, a HP company.

[Shahriar]

Thank you very much for your reply.

Master Should send Data to all slaves and Retrieve some data from each Slave.
Just like a I2C Bus System.
But the difference with this system and a Small I2C Bus System is Distance between Master and Slaves.

BTW, Each Slave is a MCU Based Circuit.

ThanX
Shahriar

[Tony_Stoynov]

Hi,
the RS485 is very good decision. Afcourse you can use CAN but if you have not a controller with a can module will be a needless work.