How does PC communicate with multi-mcus via the RS232?

stefsun · Joined: 23 May 2007 Posts: 22

PC communicates with two mcus, two mcus link with bus.
If first mcu's address is 0X00;the second mcu's address is 0x01.
PC send a address, then the two mcus both receive the address to
judge which one can receive.
If PC send a 0x00, the first mcu judge the address to enable the send interruption.
then it send data to PC, when it send all data, then it disable the send interruption.
The second mcu judge the address(0x00) to disable the interruption.

If PC send data to any of the mcus, how they works?

Who has example about communication PC with multi-mcus, give me some advice.
Thanks in advance

asmallri · Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia

Guest · Posted: Thu Nov 13, 2008 11:06 pm

thanks your reply
do you have the example about multi-mcus communication via the rs485

arunb · Joined: 08 Sep 2003 Posts: 492 Location: India

A basic example can be found in PICC\examples;directory, ex_rs485.c

Some other examples/ communication schemes regarding RS 485 have been discussed in this forum, just search for RS485 in this forum.

You can also search in google. There are many other examples..

thanks
arunb

Guest · Posted: Sat Nov 15, 2008 9:33 am

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

The only difference is that RS485 requires an extra PIC pin to tell the driver/receiver chip which direction to use, driving or receiving. In CCS this is the Enable pin in the #useRS232 statement.
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arunb · Joined: 08 Sep 2003 Posts: 492 Location: India

The other difference being that RS232 uses +12 and -12 V voltage levels to send/receive data.

While the RS 485 uses a differential voltage of +/- 5 V DC.

thanks
arunb