Maybe I'm stupid or old / WTB Null modem DB9

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Forums › Offers and Wanted › Maybe I'm stupid or old / WTB Null modem DB9

Talkiet

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#283812 13-Mar-2021 17:55

But I can't find M-F DB9 null modem adaptor in Chch. Jaycar don't have them, PBtech want $10 to ship them to Chch, there's NONE listed on Trademe and I can't wait 3 months to get them out of China... Am I that old that no-one knows what RS232 is anymore?

Anyone got a couple of DB9 M-F null modem adaptors they could sell me for a reasonable price? At the moment I have a couple of jumpers crossing over the cable which is ugly++ and isn't conducive to being carried around as a test platform doing some LORA signal mapping...

Or suggestions of places that won't charge more for the postage than the parts?

Cheers - N

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

SirHumphreyAppleby

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#2673927 13-Mar-2021 18:00

You are not alone. I still use null modem cables (not adaptors, sorry, cables are cheaper). I even have new-ish computers I use them with (PC Engines APU2 boards).

clinty

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#2673929 13-Mar-2021 18:11

I think I have some null modem M-M DB-9 adaptors, and matching DB-9 F-M adaptors.

The combo worked for us

Will check on Monday when I get in and will PM

How many do you need?

Clint

Rikkitic

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#2673945 13-Mar-2021 18:59

I think I might have a couple of very old break out boxes lying around somewhere. I could take a look for them if that might help. You can wire them any way you want.

Plesse igmore amd axxept applogies in adbance fir anu typos

Behodar

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#2673947 13-Mar-2021 19:09

This any good? It's DE-9 rather than DB-9, but that's probably what you meant anyway... (a lot of people get it wrong!)

https://nz.rs-online.com/web/p/serial-cable-assemblies/1828783/

MadEngineer

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#2673997 13-Mar-2021 21:18

^ not a null modem cable.

You're not on Atlantis anymore, Duncan Idaho.

Behodar

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#2674007 13-Mar-2021 21:58

Right you are. It's been a long time...

Talkiet

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#2674013 13-Mar-2021 22:26

clinty: I think I have some null modem M-M DB-9 adaptors, and matching DB-9 F-M adaptors.

The combo worked for us

Will check on Monday when I get in and will PM

How many do you need?

Clint

That would be awesome thanks... please do PM me with what you can offer.

Cheers - N

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

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Talkiet

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#2674037 13-Mar-2021 23:31

Prototyping situations call for desperate measures :-)

ANd no, swapping the TTL inputs RX/TX didn't work.

I'll still need a proper solution but this should at least let me functionally check the comms!

Cheers - N

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

Talkiet

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#2674041 14-Mar-2021 00:15

Eff it - I liked RS485 better anyway, I found TTL to RS485 converters locally for $3.50 and I'll be able to use a single connector for A/B and power... Plus RS485 cabling is figuratively anything slightly conductive you have hanging around...

Cheers - N

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

frankv

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#2675058 15-Mar-2021 16:48

Sorry, I can't help you.

But you need to be very clear about what you want. Null-modem (and RS232) covers a multitude of sins.

What is your definition of a null-modem cable? RX/TX crossed plus GND? What about all the various handshake lines? Do they need to be connected (crossed over) or can they be looped back at each end? Or ignored?

BTW, your photo doesn't show the GND being connected... without that it won't work.

Talkiet

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#2675062 15-Mar-2021 17:04

I had already pulled GND at that stage and just put them together with the hacked crossover RX/TX on another RS232 adaptor for the photo. The device needs only RX/TX/GND - doesn't need CTS or anything else.

As it turns out, I've decided to just use RS485 instead due to a much easier testing and integration outcome. (I can create a single connector into the LORA DTU with A/B/VCC/GND instead of RS232 and a power connector.

With the troubles I had finding the right RS232 bits I think it's not sensible to use that if I don't have to.

Cheers - N

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.