# Dual RS-232?



## j2sgam (Feb 21, 2008)

I have a question about control for a Sirius tuner from 2 systems. Basically Im trying to control it from both a Pronto remote and NetStreams, but there is only 1 232 input on the back of the Sirius. The tuner will only allow 1 type of control, either rs232 or IR and I would prefer 232. Does anybody know a cost-effective way to make this happen?


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## Anthony (Oct 5, 2006)

I haven't used it in home integration, but 232 commands are often "shouted", that is, they are transmitted in a stream with no care for a return message or even waiting for any negotiation (i.e. data set ready, clear to send, etc).

So if you need two things to bark commands into one port, you can just wire them in parallel. If they both transmit at the same time, things will get ugly and nothing will work. But if they are well behaved it might.

There are serial communication software packages available for computers as well. If the computer had several ports, it could receive on several and transmit on one and negotiate who got to talk when. These can get very complicated though (at work we just write our own control programs when issues like this come up).

I do not know of a passive box that could combine the signals, but I would not be surprised if it exists. There is a lot of legacy serial/RS232 stuff out there and you can't be alone in this problem. But like I said above, the "passive" solution only works if the device is well-behaved and is not trying to 2-way communicate all the time to both controllers.

Good luck.


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## j2sgam (Feb 21, 2008)

Thanks Anthony, but NetStreans needs the 2-way communication. I thought about getting a 1/8" mini Y-cable and control both with IR, but I need the 2-way, so that is out the window. The Pronto does not need to be talked back to though..


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## Anthony (Oct 5, 2006)

I talked this over with a coworker and the parallel wouldn't work either. The non-transmitting would hold low at -5V and the transmit would transmit at +5V peak, so they would zero out and the receive pin would not know what to think.

I know in the advanced installations that all the 232 stuff is in a "bus" configuration, which is parallel, but in that case all the devices are "listen" and there is only one controller (which isn't the case here).

:dunno: Hmm, I need to think about this a little more. We deal with weird serial communication stuff like this all the time at work, so I should know this


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