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How can i wire an unusual 16-pin null modem cable to DE9 instead of DB25

kyodai

Experienced Member
Joined
Jan 26, 2011
Messages
467
Location
Kerpen, Germany
OK, I admit i have never been a big cable guy.

So this fancy 80C88 based unit with a Vacuum fluorescent display and DR-DOS 3.41...

Symbol VRC-6940 if anyone is interested. Just LOVE the display. However - the ports are not such standard...

It has this odd 16-pin round jack for a nullmodem cable. The manual just says like "Connect a null modem cable with a round 16-pin plug and a 25-pin RS232 plug..." needless to say such a cable prolly only exists on the moon.

The manual was kind enough to list the pin-outs for a nullmodem cable though. Very kind!

So before I rush out and get a DB25 to DB9 adaptor (Obviously my laptop has DB9) - I thought I'd ask a cable guru here since I am sure you could also wire it directly to DB9 (If you are clever enough).

As I said I am not much of a cable guy (no pun intended! Although i liked the movie). So any help?

nullmo.jpg
 

ldkraemer

Veteran Member
Joined
Mar 14, 2013
Messages
2,319
Location
Chaffee, MO
I hope you are luck enough to locate the 16 Pin Round Connector.

NULL MODEM
16 Pin Circular DB9
2 RX <-------------- TX 3
3 TX --------------> RX 2

5 GND -------------- GND 5

4 DTR----| |----DTR 4
6 DSR<---| |--->DSR 6
1 DCD<---| |--->DCD 1

7 RTS----| |----RTS 7
8 CTS<---| |--->CTS 8

But I'd try the FULL HANDSHAKE

FULL HANDSHAKE
16 Pin Circular DB9
2 RX <-------------- TX 3
3 TX --------------> RX 2

5 GND -------------- GND 5

4 DTR-----------|--->DSR 6
|--->DCD 1

6 DSR<---|-----------DTR 4
1 DCD<---|

8 CTS<---------------RTS 7
7 RTS--------------->CTS 8


Larry
 

KC9UDX

Space Commander
Joined
Jan 27, 2014
Messages
7,468
Location
Lutenblag
I never make null modem cables unless it's part of a permanent connection that will never be removed. It's far less confusing to make a "straight" cable, and add a null modem adapter.

Are you sure Symbol doesn't sell the cable you need? I'll bet they do. That might be easier than sourcing the connector let alone building the cable.
 

kyodai

Experienced Member
Joined
Jan 26, 2011
Messages
467
Location
Kerpen, Germany
Thanks to Larry for the pinout, i will try that.

I don't think i can get the round connector, but i will find some way to sqeeze cables in there, or maybe paper clips or such? I will find a way.

Unfortunately i haven't seen that cable anywhere. The hanbook mentions it "like it's a standard cable you can get at any radio shack", but no part number, nothing. I have seen a cable that looks like what i wanna do (With DB9) but it's supposedly for a different model and it's like 50 dollars with shipping (more than what i paid for this thing).
 

BrianS

Experienced Member
Joined
Oct 10, 2013
Messages
179
Can you post a picture of the connector on the computer, along with it's diameter? You never know what is in someone's junk bin.
 

kyodai

Experienced Member
Joined
Jan 26, 2011
Messages
467
Location
Kerpen, Germany
Busy weekend, so i didn't really have much time to play with this machine.

However, just browsing around a bit on the flash and ROM drives i noticed it seems to have some kinda TFTP client on it. It does have a wifi card built-in but I don't think i have the antennas for it - however - for a very short distance it should even work without the antennas, so before i try making the null modem cable I'll first see if i can connect it to my wifi.

That would actually be pretty cool to have an 80c88 with DR DOS 3.41 hooked up to wifi. :p
 

Charlie-III

Member
Joined
Dec 6, 2016
Messages
12
Location
N. NJ, 07456
Busy weekend, so i didn't really have much time to play with this machine.

However, just browsing around a bit on the flash and ROM drives i noticed it seems to have some kinda TFTP client on it. It does have a wifi card built-in but I don't think i have the antennas for it - however - for a very short distance it should even work without the antennas, so before i try making the null modem cable I'll first see if i can connect it to my wifi.

That would actually be pretty cool to have an 80c88 with DR DOS 3.41 hooked up to wifi. :p

A month late, but, I would NOT run a TX without an antenna connected. That can fry parts in the TX section.
 
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