Need to get an RS-485 and RS-232 from a single RS-232 1

[alcazar]

Hello everyone, i need to know if it is possible to get an RS232 port and an RS-485 port from a single RS-232 port. I know it is possible to change an RS-232 to an RS-422 or 485, but what i need is to have two usable and independent ports from a single port. Does anybody know if this is possible? i hope somebody can help out with this issue.

 

[danw2]

What about two 232-485 converters?

RS-232 port >
> 232/485 converter
>485 multidrop port
>485 multidrop port
. . . . . .
> 485/232 converter = 2nd RS-232 port

 

[VEBill]

"...two usable and independent ports from a single port..."

Almost by definition, no. Given that common sense answer, almost anything is possible if you're willing to hack enough.

One could even imagine an external box (custom design) to do exactly what you want (within the speed limits of the existing circuit).

Converting standards is easy.

http://www.blackbox.com

Making two from one is the tricky bit.

 

[alcazar]

Thanks VE1BLL (Military), i´ll check that link to see if i can find anything helpfull.

danw2 (Industrial), i didn´t understant what you ment with that, was it that there is a device that turns one RS-232 in two RS-485? that would work just fine!!! do you know where one of such devices can be bought? if you do, please let me know.

 

[MacGyverS2000]

I doubt you'll find a 2-from-1 deal like you ask without designing it yourself, though you could find plenty of USB to 232/485 "converters"... depending on your application one of those might work well.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[LionelHutz]

Convert the 232 port to 485. Once you have 485 you can add 32 devices to the 485 buss. So, add a 485 to 232 converter to get a 232 port.

You will have to use the 232 ports as if they are 485 ports by using some sort of device addressing scheme. a 232 serial communications protocol that doesn't include an addressing scheme won't work on a multi-drop buss.

B&B Electronics makes all kinds of serial converters.

 

[subspacedarkspace]

The MAX3160/MAX3161/MAX3162 are programmable RS-232/RS-485/422 multiprotocol transceivers.

MAX3160, MAX3161, MAX3162
+3.0V to +5.5V, 1µA, RS-232/RS-485/422 Multiprotocol Transceivers

 

[danw2]

Thank you, LinonelHutz, for describing verbally
"Convert the 232 port to 485. Once you have 485 you can add 32 devices to the 485 buss. So, add a 485 to 232 converter to get a 232 port."
what I tried to convey in another fashion.

One comment on the addressing:
"You will have to use the 232 ports as if they are 485 ports by using some sort of device addressing scheme. a 232 serial communications protocol that doesn't include an addressing scheme won't work on a multi-drop buss."

One could have a multidrop topology of listeners only, (no response, no talkers) where addressing wouldn't be needed, ala AM radio broadcast over the internet.

The 485 circuit essentially 'broadcasts' whatever the source RS-232 port transmits. That might work, depending on what the OP is trying to achieve.

It isn't even clear whether the 485 is needed for multidrop or for distance.

Or clear whether this is a circuit design or implementation where only one 232 port is avialable, but 2 devices need to hear the source. Or an attempt at working around the point-to-ponit limitations of RS-232 . . .

Dan

 

[MikeHalloran]

A friend of mine built a system using multidrop RS-232 with addressing, and BASIC Stamps as nodes, mostly listeners. It worked well enough to sell.

Another friend addressed an electronic scale and an electronic syringe drive, both from the (single) serial port of his Mac, at two different baud rates with no addressing. There were some code collisions with single character commands for one device being received and acted on by the other device, but only for a set of commands he didn't need for the application.

Sometimes you're better off not knowing any better...



Mike Halloran
Pembroke Pines, FL, USA

 

[LionelHutz]

Mike, if you have one master then RS232 could work as multidrop. Much the same idea as RS422 without the better distance capability and noise immunity.

Yes, it could be possible to communicate on a RS485 network without addressing but it makes life tougher.

Now, the origional post asked for independant ports and I'm still not sure any of this satifies that requirement. You can't make 2 completely independant RS232 ports out of one.