How to Connect RS422 to Laptop?

samadrazm · Apr 22, 2014

Hi,

Does someone know how I can I connect RS422 port to my laptop. There are adapters to do so, but they are quite expensive. Is there anyway I can build the adapter by myself?

PS: The RS422 interface is located on a serial module (CP441) on a rack with Siemens S400 series CPU. The interface is used to connect a weigh scale to the PLC. But I cannot get the communication to work. So I am trying to connect it to my laptop for fault finding.

Any suggestion.

Thanks,
Samad

James Mcquade · Apr 22, 2014

samadrazm,

you can buy a usb to serial adapter for about $20.

i just bought one and it works great.

james

samadrazm · Apr 22, 2014

Both RS422 and RS232 are serial.

I have serial comms on my laptop but it is RS232, I need to connect to RS422.

Thanks

KalleOlsen · Apr 22, 2014

I have occationally used similar ones to these:
http://www.ebay.com/itm/New-Serial-...t=BI_Control_Systems_PLCs&hash=item3a79a98306

I've mostly used 485 mode (422 with latches).

You'll need additional 5VDC power supply, I used one from an old broken mobile phone. Maybe you can find 5V on a pin on the CP-card.

Kalle

samadrazm · Apr 22, 2014

Thanks,
I am confused to why we need an extra 5VDC. For example I have seen this adapter. Is there any reason why it is not working for my application?

2.4M IC690ACC901 RS232/RS422 Adapter PLC Programming Cable for GE 90-30

It says it is for GE PLC, but isn't standard cable for all purposes?

Thanks.

geniusintraining · Apr 22, 2014

What is it you are connecting to? if its the 400 why dont you use a MPI, the GE cable will not work on a Siemens PLC

samadrazm · Apr 22, 2014

The thing is I have trouble to connect a CP441 to a weigh scale using RS422.
I want to connect my laptop to the serial CP module and see if I can send o receive anything. It is purely to test my program and if the config and connection I have made are correct.

geniusintraining · Apr 22, 2014

Do you have a scope ? if you know the pins you are writing and reading to/from you should be able to see it

samadrazm · Apr 22, 2014

Thanks for the suggestion geniusintraining,

I will try it tomorrow and let you know.

Thanks

ndzied1 · Apr 22, 2014

Not sure what you consider expensive.

I have had good luck with these:
http://www.bb-elec.com/Products/USB...dapters/In-line-USB-to-Serial-Converters.aspx

How to Connect RS422 to Laptop?

samadrazm

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