2 Devices to one Rs232 port? Is it possible?

[egg0900]

Is it possible to send two different signals to one rs232 port? Each would be communicating at different times.... If so would you show a example? Please....

 

[patroclus]

Well, RS-232 only supports one emiter and one reciever, at least at the same time. If you want two emiters, for example, maybe you could use multiplexing, by only conecting to the port one of them (I think about tri-state buffer drivers for the task).

I only know thwe theory, never tried. Maybe someone can help you there. good luck.

 

[jem]

An oldie, but still good, device for that is the LT1180. It has an ON/OFF control line, and when OFF. all RS232 outputs disconnect from the line, and are not affected by other Tx's on the same line.

 

[mugzzzzy]

hi,

if it is a true RS-232 interface u could use the STD (secondery transmit data) its the pin 14 of the D-type connector....

dirty done deal and cheap.... 8)

 

[mugzzzzy]

sorry if its to transmit to one RS-232 port...well u should use the SRD (secondery received data) pin 16....


:lol:

 

[aryajur]

A simple solution would be to transmit an identity byte first in all communications, that way u do not neet to enable or disable any device connected to the same RS-232 port and by that u can at least theoretically connect 256 devices to the same RS-232 port, but they should all be synchronised in such a way as no 2 of them can transmit at once. This can be achieved by making 1 device the master which issues time slots to all.
This way is the simplest since it will not require any extra hardware.

 

[mugzzzzy]

hi,
if ur using software to manipulate ur thing why not using the ASCII value 0x11 DC1 (deivce control 1) and 0x12 DC2 (device control 2) hence u only have 2 device using the RS-2323 port...much easier

:wink:

 

[mugzzzzy]

if its a true rs232 port and u only have 2 device communicating to it...u better off using the RD signal for ur first device and SRD signal for ur second device...but they can both communicate at same time ..so all u have is a software to jump from one device to the other

let me know if was helpfull

 

[kinjalgp]

Using MODBUS or similar protocols, it is possible to put more than one devices on same line. Ofcourse for long distance, you need to convert RS232 to RS485 but the concept remains same.

 

[panic mode]

Is it possible to send two different signals to one rs232 port? Each would be communicating at different times.... If so would you show a example? Please....

It is possible... with some limitations...
One thing you could do (and it is very common practice) is to
use RS232 multiplexer such as B&B. Now these things do cost
a little and require some programming.
But before I kill my day by writing a novel, why don't you simply
explain what exactly you need to do. Good question is half an answer...

 

[delabs]

use CD4052 for switching rxd and txd

you can use a cmos CD4052 analog mux, will work for digital too, use it like a 4PDT (four pole dual throw) switch for 4 devices, control mux by 2 port outputs.

look at my circuits collection **broken link removed** for details on using 4051, 52, 53.