Multiplying a PC's serial output

Hello, I suppose this sort of qualifies as electronics design...

We're looking at splitting the signal from a laptop's serial port in a way that is probably going to need some electronic support. The signal is actually ASCII output from a court reporter's laptop. Data travels one way only, out from the reporter.

There's a passive system that's basically just a plastic splitter box , but it limits to five outputs and is intended for temporary use around a table.

These folks, however, want a permanent install in a larger room, so there's maybe 10 - 12 drops and perhaps a few hundred feet of cable. We suspect that's a bit much to push from the laptop and want to be sure that the data never fades or corrupts on the line and that nothing ever gets damaged. There's lots of excess cat5 cable installed under the room, so if that can be used installation should be simple..

Does anyone know of readily available devices for such a task?

Thanks!

-pk

Reply to
Patrick Keenan
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Not sure, but you really want to opto-isolate all of the PCs. I've blown up many computers by plugging in serial cables. (I do embedded development thus I tend to plug a lot of strange things together.)

I've seen as much as 70 volts difference between grounds on different equipment - enough to burn chips off the motherboard.

Serial ports are my favorite way to destroy equipment. Heck, I shipped one board back today for a post-mortem because the serial port quit working; I suspect due to some sort of ground problem....

Look at offerings from Black Box. I'd also think about something like the TS7300 from embeddedarm.com; I think they have an FPGA bitstream with something like 20 or 30 serial ports for that hardware.

--Yan

Reply to
CptDondo

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Reply to
Meat Plow

Thanks! I've seen this kind of thing. but am not sure that it actually will meet the limitations of this particular application, in particular the software running at the target PC. Certainly does bear investigation, though and I will get a couple as it looks like it addresses part of how to extend this application (which can otherwise be well beyond obscenely expensive).

thanks again.

-pk

Reply to
Patrick Keenan

Frankly that's one of my main concerns and I've been looking at BlackBox and other spots, and the various serial line drivers and isolators. Just not sure how they actually go together. To use these as an example,

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in particular the 9SPOP2,

there'd be one at each serial port and basically a bus.. kind of a rake shape, not a Y - of wire between?

Thanks again for your comments.

-pk

Reply to
Patrick Keenan

Reply to
Andy

One answer, is to get RS232 to RS485 converter units. These are available from industrial suppliers, in either Din rail mount versions, or small standalone boxes. RS485, gives you support for the larger number of drops, and some are available with opto-isolation as well. This gives you a good 'safe' solution. Go to

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and look at their TCC-801 (avoids need for power supplies on the listening points). Alternatively, as you may start finding that the other computers are less and less likely to have RS232 serial ports, consider a USB to RS485 adapter for the listening locations.

Best Wishes

Reply to
Roger Hamlett

A vendor just sent me this:

8018630000 Weidmuller minicoupler 5VDC input, 5-48VDC output

They're about $4 ea, din-rail mountable, and if I understand things correctly, you could just run a block of these on your TX and GND, and then connect the other laptops to the opto-isolated outputs. You'd have to think through the power supplies (you'd need at least 2, one for each side of the opto isolation), and possibly one for each laptop. But it's a lot cheaper than individual opto-isolators, and with individual power supplies you'd have no problems with signal.

--Yan

Reply to
CptDondo

If that's true, then you have seriously dangerous electrical wiring, not to mention WAY out of code.

You need to get your wiring repaired before you kill somebody.

Thanks, Rich

Reply to
Rich Grise

Run a serial cable for 2,000' along a 480 VAC line and you'll get 70 V induction.....

Meets code but you'd better have serious isolation.

A log of what we do is not earthed because of groundstrikes from lighting and because the equipment is mobile and very large. So it's possible to get floating ground potential between equipment.

We test for that in the lab but sometimes I screw up and blow something off the wall.

Reply to
CptDondo

There are lots of print server boxes that put a port (or three) onto Ethernet. If one is used next to your court reporter, the data would be available (with some software diddling) to any user on the local Ethernet branch. Just use Ethernet broadcast features.

If you have lots of CAT5 cable, it's probably trivial to put a suitable Ethernet port at each station, and connect 'em to a small hub.

If the reporter's box is programmable enough, it could be done through any available instant-messaging software, too; I don't know how important the 'ASCII output on serial port' constraint is.

Reply to
whit3rd

Thanks to all who have responded to this question.

In case it's useful to anyone later, this is what turns out to be not just the most appropriate but likely the best solution:

TCP-Com, from TAL Tech.

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"TCP-Com is a software based RS232 to TCP/IP converter. TCP-Com allows any of the RS232 serial ports on your PC to interface directly to a TCP/IP network. For example, you can use TCP-Com to turn a PC into a ?Serial Device Server? so that you can connect any RS232 serial device directly to a TCP/IP network and communicate with that device from any other workstation in the same network or across the Internet.

TCP-Com can also create ?Virtual? RS232 serial ports that are actually connections to a TCP/IP port. This allows you to use existing Windows based serial communications software to send and receive data across a TCP/IP network."

Using the free-30-day-demo version, we were able to connect a reporter's system to a receiving system over a local wireless network connection. None of the custom cables or the send/receive adapter pairs, or USB-to-serial adapters, were needed.

It took us about 15 minutes to start up the systems, install the software, figure out the settings, adjust the reporting software and make the whole thing work. It'd be hard for it to be easier or less cluttered.

So we'll be recommending this, with the client simply repatching the existing network cabling to the desks that need this feed. At most, because access limits have to be imposed (particularly for in-camera sessions), another router will have to be installed to isolate those desks.

Thanks again, Patrick Keenan

Reply to
Patrick Keenan

Thanks to all who have responded to this question.

In case it's useful to anyone later, this is what turns out to be not just the most appropriate but likely the best solution in this specific context.

There may be other vendors of this type of redirector, but this is the one I found and tested:

TCP-Com, from TAL Tech.

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"TCP-Com is a software based RS232 to TCP/IP converter. TCP-Com allows any of the RS232 serial ports on your PC to interface directly to a TCP/IP network. For example, you can use TCP-Com to turn a PC into a "Serial Device Server" so that you can connect any RS232 serial device directly to a TCP/IP network and communicate with that device from any other workstation in the same network or across the Internet.

TCP-Com can also create "Virtual" RS232 serial ports that are actually connections to a TCP/IP port. This allows you to use existing Windows based serial communications software to send and receive data across a TCP/IP network."

Using the free-30-day-demo version, we were able to connect a reporter's system to a receiving system over a local wireless network connection. None of the custom cables or the send/receive adapter pairs, or USB-to-serial adapters, were needed.

It took us about 15 minutes to start up the systems, install the software, figure out the settings, adjust the reporting software and make the whole thing work. It'd be hard for it to be easier or less cluttered.

So we'll be recommending this, with the client simply repatching the existing network cabling to the desks that need this feed; all of the desks have multiple ethernet jacks, some of which are simply not patched to anything at the moment. At most, because access limits have to be imposed (particularly for in-camera sessions), another router will have to be installed to isolate those desks.

Thanks again, Patrick Keenan

Reply to
Patrick Keenan

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