usb to serial adapter

[dphan128]

Hi,

I'm trying to expand my test application to run on two stations by using another USB to Serial Adpater cable. But the expanded serial port doesn't work with my labVIEW test. I tried to verify using hyperterminal and also couldn't read the string correctly (it only showed some scrambled symbols).

How would I expand my test to run on two stations if I can't have another working serial port. Buying a new computer!

Please advice.

Thanks

Dan

[cmpowell]

If you seeing scrambled symbols on a serial port (USB converter or standard) you might not have the baud rate set correctly.  Run Visa Configure Serial Port.vi and programatically set the baud rate before you try your read, set the baud rate to match the baud rate of your serial device.

later
chris

[dphan128]

Baud rate was the first thing I checked, so the problem was not there. Any other idea.

Thanks

Dan

[Derek Price]

We use a Belkin USB-to-serial adapter that we picked up at a local Circuit City and have had no problems.  We use the standard VISA VIs on LV6.1 and have tested as fast as 56K.

[Flocko4040]

Perhaps trying some other converter-brands might help. Here at work we have 5 different kinds of USB-RS232 converters. We have some RS232 controlled equipment like an audio-switcher, working fine with LabVIEW and the RS-232 port of the PC. But if i want to change the connection to a USB-RS232 converter the same code will work only with one of the 5 converters.

[cmpowell]

Sorry about the baud rate advice, I use USB-RS232 converters fairly often and haven't had any problems (As much as it pains me to say it I've had good luck with the radioshack converters).  What brand converter are you using?  What are you trying to talk to? 

Another option that I've been working with are serial to ethernet converters (VLINX from B&B Elec) and they are great, the TCP vi's are easy and you can have multiple machines listening or talking to a single device (the VLINX supports 8 concurrent conncetions).

[Dennis_Knutson]

For basic troubleshooting, open hyperterminal with pins 2 and 3 shorted on the DB9 connector of the device. Set the baud rate to something low like 9600 and make sure the flow control is set to none. If whatever you type shows up in the hyperterminal window, the usb-rs232 converter is probably ok. If it's garbage characters, return it to the vendor or see if they have an updated driver. If the text looks okay, hook the converter up to something that you are familiar with and are absolutely sure about the com settings. Try the converter and see what you get.

[dphan128]

Hi Dennis,

Per your advice I tried to communicate with a different device just for troubleshooting purpose and it worked fine. So the USB-RS232 converter is not the problem. The custom board that I'm trying to communicate with has a fixed baud rate of 38400 and I can't slow it down without changing the firmware on the microcontroller. I guess I have to talk to the engineer who programs the flash so he could change the communication protocol. But still, he might argue that his protocoll works with the real serial port. For that I don't know why? 

Thank you all for your advices.

Dan

[Dennis_Knutson]

Well, if you can talk to the board with a built-in serial port but not the usb-rs232 converter, it probably is a problem with the converter. There are some that work better than others. See this thread for a solution to get some to work with VISA. I don't think it will help you though since you can't get it to work with Hyperterminal either.

[dphan128]

Thank you all. I think I'll just go get myself a serial expansion board that plugs in my PCI slot for an easy fix.