problem using usb to serial port converter communicate to PLC


Thread Starter


dear sir/madam,
I am using the usb to serial port converter
(ft8u232,from: "": ) to communicate to the PLC (model: idec,siemmen,mitsubishi....), my problem is when I
using the protocol convertor plug in to the usb-serial convertor and link to the PLC,it can't detect the serial port (I try many unit & diference model) , some of the PLC software still running uder DOS ver,they are not support DOS, according to the supplier say,I must write a driver which will allow to communicate in DOS (MSDOS comms interrupt int14,what it mean?, to develop the useful link
is "": see USB 4 DOS section), what can I do now ?,I am waste a lot of time to
test & solve this problem, still no result ,PLS help me. THANK YOU !

best regard,
[email protected]
You didn't say wich PLC or PC operating system you are using, but I have run into similar problems with Siemens S5 and 505 PLCs. I don't believe windows NT will support serial communications through the USB port. Try just plugging it in to your com port.

Daniel Chartier

I can't help you with all your PLCs, but if you go to the Siemens' support web pages ("": ), then Support, FAQ, Products and Support...), do a search on Entry ID 7843251.

This will point to a document showing the steps to install a USB to serial converter to communicate to a S7-200 PLC. It might even help for other PLCs of the S7 family.

Hope this helps,
Daniel Chartier
Actually you shpuld buy the SERIAL COM Port using USB device and not the usb to serial converter