nul modem to rs232 - Techwatch Support Forums: Digital & Satellite TV, FTA, Cable, Computers, Mobile Phones, Apple and General Tech Forums

Graig · 26-07-09, 10:01 PM

Hi I want to make up a cable to connect my laptop to my Eurovox 500, can anybody tell me the pin connections on both the USB and the rs232 nul modem I assume ths will work Cheers.

Neosophist · 27-07-09, 01:42 PM

No it wont work.

USB uses a completely different protocol to an RS232 port.

If you with to use USB->RS232 you need an IC to do the transceiving. Cheaper to buy a readymade USB-> RS232 adapater, which will have all the required hardware inside.

Failing that if you have a DB9 port you can make a Null modem cable with the following schematic.

However, Null modem cables are extreemly cheap so making them isn't economically viable anymore.

Graig · 29-07-09, 03:00 PM

Many thanks to Neosophist for his very clear easy to understand answer to my question, I was under the impression that it would only be a matter of cutting an end off 2 spare cables and connecting the 2 as required, I wasn't aware there would have to be a matching device between the two. Once again many thanks.

PS I have located item number 120348974363 on ebay witch claims to be the ultimate for this purpose, and costs £8.89 delivered.
The guy selling has an excellant record with ebay and claims to have sold over 500. I eagerly await delivery.

26-07-09, 10:01 PM	#1 (permalink)
Graig Junior Member Join Date: Jul 2009 Posts: 2 Thanks: 1 Thanked 0 Times in 0 Posts	nul modem to rs232 Hi I want to make up a cable to connect my laptop to my Eurovox 500, can anybody tell me the pin connections on both the USB and the rs232 nul modem I assume ths will work Cheers.

27-07-09, 01:42 PM	#2 (permalink)
Neosophist Member Join Date: Dec 2008 Posts: 62 Thanks: 4 Thanked 19 Times in 11 Posts	Re: nul modem to rs232 No it wont work. USB uses a completely different protocol to an RS232 port. If you with to use USB->RS232 you need an IC to do the transceiving. Cheaper to buy a readymade USB-> RS232 adapater, which will have all the required hardware inside. Failing that if you have a DB9 port you can make a Null modem cable with the following schematic. However, Null modem cables are extreemly cheap so making them isn't economically viable anymore.

29-07-09, 03:00 PM	#3 (permalink)
Graig Junior Member Join Date: Jul 2009 Posts: 2 Thanks: 1 Thanked 0 Times in 0 Posts	Re: nul modem to rs232 Many thanks to Neosophist for his very clear easy to understand answer to my question, I was under the impression that it would only be a matter of cutting an end off 2 spare cables and connecting the 2 as required, I wasn't aware there would have to be a matching device between the two. Once again many thanks. PS I have located item number 120348974363 on ebay witch claims to be the ultimate for this purpose, and costs £8.89 delivered. The guy selling has an excellant record with ebay and claims to have sold over 500. I eagerly await delivery.

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