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kirkoff.itgo.com   
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So there I was, I had an RS232 cable. My brother in law bought it from
radio shack, thinking it was a Null modem for playing doom. Well, it never
worked. Flash forward about 2-3 years. Yup, its 1999, and I still have
that same old cable that never worked. Well, my friend Andrew had an old
386. Upon inspection this is what was in the system: A 386sx/16, 2MB of
ram, a 42 MB IDE hard drive, 36MB(?) formated, a 1MB SVGA card, and old
Packard Bell 14', and a good old 101 enhanced keyboard. He brought over
his external 28.8k Cardinal modem. I installed some software (QL2 Fax/Dos)
that works good as terminal software, which I had laying around. We
connected the modems together, and did an ATA, and a ATDr on the modems
and tested the com Ports, and found out that you can only get to 19200bps.
The previous night, I had mapped out what pins on the RS232 were connected
to which. It was simply that Pin 1 went to Pin 1, Pin 2 to Pin 2, etc. I
went on the Internet, and mapped out what pins need to go to which to make
a null modem. So we started to work, here is what you need:
!!NOTE!! I will not be held responsible for ANY problems you have. This page is simply a reference to those, like me who wanted to make a null modem.Now, my cable was shielded, which is of coarse not REQUIRED, but is helpful. Now, this is the fun part. Take a knife, and cut in to the cable near, but not too close to the connecter, remember, if you need more of a wire, it is very helpful is you can move back on either side to get it. When you cut in, treat it like skin(if you were doing surgery), only cut as deep as the shielding, in other words, avoid at ALL cost cutting the pin wires before necessary. You'll need about a three inch + section of wire, now, snip away the shielding, that looks like a thatch mat, it is a mesh of bare wires wires. Once it is away from that section, make sure to cut off the foil that is there. You should now see exposed some colored wires. Snip one of them, and check to see if it matches up to the pin diagram. If it doesn't, you will have to cut all of them. But if it does, check one or two more, and see if it they match. At this point I should say that the probe I had was to big to fit in the hole, and that a staple, or little wire worked good to make a pin to test. There are probably some plastic fibers in the middle of the colored wires. Cut that out to make working on the cable easier. If you've never done it, you'll need instructions on how to make expose the conductor. You can use fire, but that's not such a good idea in this case, so the best way is to take the end of the wire, and put it up against your finger. Then cut hardly in to it with your scissors, rotate it, and do another cut, the pull the it off with your finger nail. It may take some practice, so get something like 24 or 26 gauge wire, and practice. Then make the proper connections according to the diagram. You'll need to solder the extra wire from the foil to the other foil. I thought it important to give the colors of my wire as I would have liked it just in case it would've helped. Then separate the wires and test it. Make sure the port speed isn't set too high. If it didn't work, keep testing it to see what errors you may have, and try to fix them. If you get it to work, then put some tape to separate the soldering joints. Wrap the tin foil around the exposed part, and then put tape around the whole part where there is tin foil, and over some of the insulator. With any luck you've just made a cable good enough to use for a dumb terminal like me. I have had trouble with it dropping a bit or two every 500 or more bytes. As it turns out, the URAT on the 386 can only handle a connection speed of 9600 baud. After that it drops bits when it gets too bombarded.
One connector is assembled from each side of the hyphens. The frame ground on the 25 pin plug is optional and should only be connected on one side of the cable. If you need Data Carrier Detect (DCD) on your cable (BBS programs, Unix Getty and so on) then:
The connections for DCD should be made on the same end of the cable. Null Modem Pin Connetion:
Where is Pin 1?
If you need information on the RS-232 standard please see: To make a hopefully easier step by step, I grabbed this from http://www.newenterprises.com/~gduncan/connections/null-mod.html Who said Fearing that it might dissappear, this information was lifted from http://www.loop-back.com, who gleaned pieces from fly.hiwaay.net/~jfrohwei/tech/null-mod.html Who says: "I swiped this data from http://unix1.hials.no/~aoy/home_uk.html, it was so darn useful I was afraid it might disappear." Good thinking. It appears that the last host is down. |
