RS-232 DB25 Breakout strip

"Dave Houston" wrote

Wow! Look at all the serial-flavored goodies!

Plus, lots of technical information that I'm going to need about connecting RS-232 and 485 devices. That will be handy because in addition to the RS-232 control input, these MUX boxes have a RS-485 port to connect to each other.

Lots of other information including the story behind the gradual disappearance of serial ports from PC's:

"A "Legacy Removal Roadmap" has been established at the Intel Developers Forum in 1999 for the phasing out of "Legacy Technologies" in PCs. The first to go in this timeline was the ISA slot, used for adding special function cards to the available PC slots. Intel's Legacy Removal Roadmap calls for the gradual phase out of other technologies. On the list for removal are the following: Gameport/MIDI, PS2, Serial, Parallel, IDE, Floppy, VGA, and eventually all user-accessible slots."

Oy!

Still looking for the breakout connector but I am sure it's here somewhere . . .

-- Bobby G.

That may be a product whose time has passed and that they've dropped.

They have breakout boards of almost every possible type.

In my rummage through the junkbin I found an old DB25 female panel mount connector that is connected to a colored ribbon cable. I think it's got enough wires for me to extract the RS-232 lines from MUX and interface them to my PC so I can use Hyperterm or some other terminal program to send ASCII to the unit via the RS-232 interface. I was trying to figure out how to move the pins inside the connector when I saw your message and I clicked on the link you sent. That's *just* what I had in mind. It's pretty damn close to magic!!!! Damn. Dave scores a home run.

Thanks again, Dave!

-- Bobby G.

I've got a MUX with a DB-25 connector on the back. The manual tells me that the pins are arranged as follows:

01 - Alarm Input 1 02 - Alarm Input 2 03 - Alarm Input 3 04 - Alarm Input 4 05 - Alarm Input 5 06 - Alarm Input 6 07 - Alarm Input 7 08 - Alarm Input 8 09 - RS-232 RX Input 10 - RS-232 TX Input 11 - RS-232 RX Output 12 - RS-232 TX Output 13 - VCR Trigger Input 14 - Alarm Input 9 15 - Alarm Input 10 16 - Alarm Input 11 17 - Alarm Input 12 18 - Alarm Input 13 19 - Alarm Input 14 20 - Alarm Input 15 21 - Alarm Input 16 22 - Alarm Hold Input 23 - Alarm Output Common 24 - Alarm Output NC 25 - Alarm Output NO

I'm trying to hook this up to a PC using a 9 pin serial port with a DB25 adapter. I looked at the diagram for the standard RS-232 serial port pinouts:

At first I had hoped they used a standard configuration and chose the location for the RS-232 lines based on where they appear on standard PC DB-25. But pins 9-12 on a standard connector are test pins and whatnot. The MUX pinout also uses pin 1 for an alarm channel where the standard has it marked "ground."

Does anyone have any suggestions how to wire the MUX pinout above so that I can communicate with it via a 9 or 25 pin PC serial port?

I'm using a 25 to 9 pin serial adapter, FWIW, because I already have a DB25 connector with a ribbon cable coming out that I can easily wire to the MUX until my Winford Engineering breakout box arrives.

TIA!

-- Bobby G.

RS-232 only requires 3 wires TX RX and ground for non-hardware handshaking communication. On a 9 pin connector those are on pins 3, 2 and 5 respectively. No standard serial cable is going to work with the pinout you have listed above.

My guess is that on pins 9 thru 12 two of those pins are grounds and the other two are TX and RX. The first check would be to probe those pins with a multimeter and see if any of 9 thru 12 were connected together. If they are those are likely the ground pin.

In an earlier post you mentioned "these MUX boxes have a RS-485 port to connect to each other". Is it possible that pins 9 thru 12 are actually RS-485 which uses 4 wires?

Do you have the serial protocol (baud, stop bit, parity and command structure) for this box?

I didn't think so. But the bigger problem is: Which pin on the MUX is a ground pin?

Would you test for continuity with the unit off? I'm only marginally competent with electronics, I'm afraid. I considered looking for voltage on the pins with the unit running, but wasn't sure which pin to use as ground. I was leaning towards pin 23 - Alarm Output Common but it's really just a guess. I suppose I could pop the case and try tracing the pins in question by eye.

Very doubtful since it also has two jacks using what look like CAT-5 connectors labelled "RS-485 IN" and "OUT" below the DB-25 connector. Creating a null modem cable to connect the two units seems pretty straightforward - I think. But first, I need to access the box via RS-232 because there's no point in interconnecting them if I can't talk to them.

I have a list of all the ASCII and hex commands it understands. The protocol is listed for the usual range of 1200-19600 settings. There doesn't seem to be much more about serial networking other than a pinout of the RS-485 connection and which pins on that connector to short to terminate the network.

Thanks for the response!

-- Bobby G.

Do I want the DIN rail or the non-DIN version? The DIN stuff looks like it would be easier to remove and replace. Is there some other benefit?

TIA,

-- Bobby G.

Only if you have a DIN rail. DIN rails (C shaped channels) are used here in industrial control cabinets. In Europe they are also used in residences in enclosures designed to hold a DIN rail.

For the first bit of testing I would have the unit off and check for continuity between any two pins in the group 9 thru 12. If you find continuity between any of those two pins they are most likely ground.

If there is no continuity between any of the pins you will need to open the thing up and start tracing. The ground pin(s) will likely go back to the biggest trace on the circuit board. I would stick to pins 9 thru 12 for serial communications until I was sure something else was required.

Once you have found the ground then sorting out the RX and TX is trial and error since "TX Input" and "RX Output" are fairly meaningless. Many serial devices will transmit a string when they power up. That is how I have found many a TD pin and the baud, data bit, parity and stop bit settings.

Good luck!

They look to be pretty cheap on Ebay. Anything that helps keep the wiring in line is useful. I saw an old "This Old House" today where they explored the bowels of a very high end home. Six miles of wire of all sorts ended up in the wire closet in the basement. It was an 80 dimmer Centralite-sort of setup. I've never seen so much wire in a residence.

-- Bobby G.

That's what I will do to start.

I will visually trace the wire anyway just to be on the safe side.

OK - that sounds like a plan. It will be a while until the breakout box arrives anyway. Tonight I have to fire up the new PC to make sure all the components are OK. I'm glad to see AMD finally got smart and increased the surface area of the CPU and beefed up the mounting of enormous 5 pound cooling fan - increased to 80mm from the puny little 40mm fans of yesteryear. There's still a great satisfaction in cobbling all the separate pieces together and getting it to light up and not burn up when you throw the switch.

Thanks for your input, Lewis. I appreciate it!

-- Bobby G.

These guys were using structured cable with 2 RG6QS and 2 CAT-5 cables in every jacket and I don't think they were counting the separate cables in the length total! This home's automation center looked like a nuke sub's missile room. They even had a giant power conditioner with a coil that looked to be over a foot in diameter. It was very impressive. I'm only sorry I didn't tape it.

One thing's for sure. Modern home automation = boatloads of wire!

-- Bobby G.

"Robert Green" wrote >

This got me thinking -- 6 miles of wire sounds like a lot, but it really is not that much. I recently built a house and did the LV pre-wiring myself. This is a modestly-sized home (2200 sq. ft.) single story home. I used ~1000' of bundled cable (2 cat5, 2 coax), so thats 4000 ft. right there. Then I used an addition ~700 ft. of cat5. All of that was just for the phone, network, and video outlets. Then I ran a ton more 22/4 wire for security pre-wire -- home-run to each window, door, and locations for motion (indoor and outdoor), glass break, thermostats, smoke, heat and CO detectors, as well as keypads, sounders, etc. I figure I ran over 2000 ft. of that wire.

So totaled up, I have about a mile and a half of wire (w/o counting lighting wire), and my home is nowhere near a "very high end home". When I finish off the basement (another 2100 sq. ft.) I will have run over 2 1/2 miles of LV wire.

Kurt

We area starting to plan our next home. LV equipment and wire are a distinct line item and the cost allocated to it is climbing rapidly