How can I connect more than 1 RS232 device to a single micro?

Hi all,
I'd like to connect more than one RS232-device to the one RS232 being free
on my SBC.
If I used RS485 I had to use a special prototcol, which besides the data
containes the address of the slave device the master wants to speak to. No
problem on the master's side. But those devices are completely unaware of
anything other than one master connected to them. And as it is not possible
for me to change the software of those devices (to tell them to listen to an
address byte coming over a RS485 network), this solution seems to be ruled
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I found switchers being advertised, doing exactly what I
need. But guess what, they are built to be used with PCs: Large boxes, heavy
and - expensive. Nothing for my mobile robot.
There are ICs like the DS3695A from National Semiconductor, the MAX485 from
MAXIM etc. They all have pins to enable/disable their lines. But if I
understand it right these pins have to be set by the device hosting the
chip. Or could my master enable/disable the DS3695A of a slave thus
selecting it for communication? I guess, not.
Could I use a mux (or is it a demux?). Such ICs are used to get more I/Os
than are actually available. Probably not the right thing for this job, I
don't know. If it was that easy, the Internet wouldn't offer such large and
heavy boxes.
Any hints? Any pointer is appreciated.
Many thanks and kind regards
Reply to
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If you use XON XOFF handshaking then you only need switch TX and RX, how about a toggle switch or a relay even?
best regards
Robin G Hewitt
Reply to
Robin G Hewitt
How about a network.
Reply to
chris burns
How about a network.
Reply to
chris burns
How about a network.
Reply to
chris burns
Diode OR all the Tx outputs together into your Computor Rx line and use a pullup resistor. You have to do the networking software to address each unit so they talk politely only when polled by the master.
Reply to
Gymmie Bob
No, he couldn't change the protocol he wrote.
If you only got one serial port and nothing else the only thing you can do is put a simple processor in the serial lines. These could respond to special commands and switch the serial lines for you.
Good luck,
Reply to
Peter van der Vos
Hi Peter,
thanks for your response.
Can you (or anyone here in this group) recommend one to me? Seems it should have at least 4 RS232: Host, device 1, device 2, programmer. I'd really prefer an MCU ready to use with *very* few external electronics (I'm a "softie"), like all those stamps etc. (but in difference to those with more serial lines). Outsider recommended an SX, which I'm not familiar with (yet).
Kind regards Franz GEIGER
P.S.: Thanks, of course, to all other posters too!
"Peter van der Vos" schrieb im Newsbeitrag news:
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