Two serial connections into one, transport, then split again

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themarcshow
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Two serial connections into one, transport, then split again

Post by themarcshow » Thu Sep 11, 2014 1:56 pm

Hello all,
I was wondering if anyone had ever come across a box that took two serial connections, combined them into one, transported them across a one-way link and then split out to the separate devices on the other end?

Here's my situation:
I have a Mosley STL that is configured for a single (up to) 4.8kbps serial connection one-way from our studio to our transmitter. Currently this port is being used at 300 baud for the Burk ARC-16 transmitter control channel.
I also just recently acquired an Inovonics RDS encoder that must sit out at the transmitter. I would love to run data to that via serial, but I don't have the connection.

Is there a device where I can combine the 300 baud Burk serial connection and the 2400b or 1200b connection for the Inovonics and run that in to the 4800 baud of the Mosley? A companion box on the other end then would take the 4800 serial connection and split it to the respective 300 baud for the Burkand the 2400b or 1200b connection for the RDS encoder.

I have to believe that the data sending would rarely, if ever, conflict. The RDS data only gets sent on song changes. The Burk data is rarely ever used, just if I need to make power adjustments or turn the transmitter on/off. (transmitter status data is returned to the studio burk via subcarrier audio on the FM)

Am I thinking crazy? Can something like this exist?
Thanks.
Brad Beahm
Operations Manager Platte River Radio
Hastings, Ne
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NECRAT
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Re: Two serial connections into one, transport, then split a

Post by NECRAT » Thu Sep 11, 2014 2:49 pm

Not that combines them, but you can use standard Lantronix boxes to run multiple serial signals over a single ethernet feed.
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Deep Thought
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Re: Two serial connections into one, transport, then split a

Post by Deep Thought » Thu Sep 11, 2014 3:06 pm

I read his post as saying he has one 4800 bps serial link through the STL he essentially wants to multiplex two serial data streams into. I don't know of any equipment that will to that. If he had even a slow IP link it would be simple with two serial-ethernet/ethernet-serial converter pairs, but he doesn't appear to be that lucky.
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davek
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Re: Two serial connections into one, transport, then split a

Post by davek » Thu Sep 11, 2014 4:06 pm

Quick question: what model of Mosely STL are you using?

themarcshow
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Re: Two serial connections into one, transport, then split a

Post by themarcshow » Thu Sep 11, 2014 6:25 pm

Deep Thought is right. I don't currently have the luxury of any data link other than the 4800bps serial through the STL.

The Mosley is a 6000 digital encoder (L and R audio and the single 4800 Serial) feeding the composite input of a 6010 Transmitter.
The engineer who normally handles all of our RF and built this link didn't think we'd want to use any of the other encoding schemes that allows a second com port.

The 6000 encoder actually does have a second serial port, but as we've got it configured, that serial port is inactive.
Encoder manual: http://www.moseleysb.com/mb/manuals/dsp ... manual.pdf

Other thoughts I've had were to try and diplex a 900mhz ISM band ubiquiti radio with the STL to extend ethernet. But that would require RF filters and that gets expensive fast.
Or I've thought of even using a spare Verizon 4G card to feed the RDS data for a short while until I come up with something permanent.

Thanks for the wisdom.
Brad Beahm
Operations Manager Platte River Radio
Hastings, Ne
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Dale H. Cook
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Re: Two serial connections into one, transport, then split a

Post by Dale H. Cook » Fri Sep 12, 2014 9:30 am

themarcshow wrote:The 6000 encoder actually does have a second serial port, but as we've got it configured, that serial port is inactive.
It is data port 2 that is always active. You presumably have data port 1 disabled (encoder S2-D0 and decoder S4-D0 closed). Why not enable data channel 1 and set both data channels to match their equipment?
davek wrote:Quick question: what model of Mosely STL are you using?
Yes - you've told us about the encoder, but not about the STL. Which STL transmitter/receiver you are using are crucial, as they may limit your options for configuring the data channels in the DSP6000A.
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Deep Thought
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Re: Two serial connections into one, transport, then split a

Post by Deep Thought » Fri Sep 12, 2014 1:21 pm

"feeding the composite input of a 6010 Transmitter"

Nothing about the receiver yet, though. I would imagine it is either a 6020 or 6030, both of which should be 100% compatible with anything the encoder spits out.
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Re: Two serial connections into one, transport, then split a

Post by Dale H. Cook » Fri Sep 12, 2014 1:28 pm

Deep Thought wrote:"feeding the composite input of a 6010 Transmitter"
I missed that. If it is a 6020 or 6030 the OP should be able to run both data ports and that will solve the problem.
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davek
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Re: Two serial connections into one, transport, then split a

Post by davek » Fri Sep 12, 2014 2:52 pm

Depends if the encoder/decoder have been fitted with the extra parts required to operate in 3 or 4 channel mode, which is required to run both data channels. Also, operating on 3 or 4 channel mode either requires a wider STL channel to accommodate (up to) +/-128kHz deviation, or changing the encoder/decoder to use high-efficiency mode (allowing 4 channel mode to run at +/-64kHz). To use high-efficiency mode the receiver signal level will need to be better than -80dBm.

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Re: Two serial connections into one, transport, then split a

Post by dbuckley » Sun Sep 14, 2014 3:58 pm

themarcshow wrote:Is there a device where I can combine the 300 baud Burk serial connection and the 2400b or 1200b connection for the Inovonics and run that in to the 4800 baud of the Mosley? A companion box on the other end then would take the 4800 serial connection and split it to the respective 300 baud for the Burkand the 2400b or 1200b connection for the RDS encoder.
Yes, such things do exist, and have existed for yonks, they are called serial multiplexers or stat muxes (statistical multiplexers). An example of such a product would be the Microstat 2 by Black Box.

The rise and rise of TCP/IP has seen most of this type of gear consigned to the dustbins of history, and you can pick it up stat muxes on fleabay for next to nothing, but be aware that these devices must be used in pairs, and if you don't have the instructions you'll struggle.

Edited to add: the Black Box website now lists less than a dozen products in this category, they used to have pages and pages and pages of them in the printed catalogue. Just fifteen years ago a major point on my CV was I could make all this sort of oddball serial stuff work. My how times have changed...

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Deep Thought
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Re: Two serial connections into one, transport, then split a

Post by Deep Thought » Sun Sep 14, 2014 4:08 pm

Does that work with a one-way link? It also appears to derive power from the connected device(s) which may not be compatible with the equipment.

Other than that (and the nearly $600 price for two of them) it looks promising.
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Re: Two serial connections into one, transport, then split a

Post by dbuckley » Sun Sep 14, 2014 5:38 pm

Yes, unless they are very unlike the muxes I've used, they'll happily work one-way. Certainly tech support at Black Box could answer that.

Power is easy bodged, a 12v wall wort and a custom cable.

But yes, they are very expensive for what they are. They can command this price because people who need them are the people can't afford to just run another RS232 link. It is so much cheaper to use a pair of statmuxes - even at $600 - than to get another link going.

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Re: Two serial connections into one, transport, then split a

Post by Deep Thought » Sun Sep 14, 2014 10:34 pm

For this application, though, it makes more sense to enable the second port on the STL and try that first, assuming that the rest of our assumptions about the equipment are correct. The OP's been a little light on details.
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dbuckley
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Re: Two serial connections into one, transport, then split a

Post by dbuckley » Tue Sep 16, 2014 3:41 pm

I hadn't spotted this. I've just downloaded the manual, and the DSP6000 does have two serial ports, so why wouldn't one use them...?

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davek
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Re: Two serial connections into one, transport, then split a

Post by davek » Wed Sep 17, 2014 1:27 am

If the encoder/decoder pair was only specified to be a 2 channel unit, then the parts required to operate in 4 channel mode may not have been installed (off memory this includes 2 aptX chips, another large PLCC chip and some other miscellaneous parts). This may be the situation the OP is in - he can't enable the second data channel.

To enable the second data channel, the encoder/decoder will have to be converted and configured to operate as 4 channel units. Doing this is not as straightforward as it seems (refer to my earlier post). It requires either a wider STL channel, or converting the encoder/decoder to use high-efficiency mode (assuming the path is clean and there is plenty of RX signal).

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