topic Re: modem problem in LabVIEW

modem problem

JUSTIN.YEH — Fri, 27 May 2005 06:01:41 GMT

hi:
I am testing a voip gateway using two modem to communicate through this gateway
First I use vi from modem.lib to create. It does not work all the time.
Then I decide to rewrite this vi(serial) using VISA(2.6). Problem is that modem does not respond. I have tested this environment using Hyper Terminal. It works OK.
I still don't know what's wrong. Can any one help???

I am using Windows XP
VISA 2.6
Labview 6.1

Re: modem problem

Matthew_Williams — Fri, 27 May 2005 12:10:59 GMT

Saw exactly the same behavior last night. I _think_ it is related to LV not being able to
get permission from the OS to access the serial port. Can you try rebooting the PC and
going straight to your LV app (without running hyperterm), then shutdown LV, then try
hyperterm, then back to LV? I'll be trying the same here later today and will report
back.

Matt

Re: modem problem

JUSTIN.YEH — Mon, 30 May 2005 02:47:00 GMT

Hi:
Thanks for your reply. Unfortunately, I have tried it and did not work.
One intersting thing I have found is that I did put VISA Read after last VISA Write. It will show all the strings from all VISA Write. My guess is that it was stored at a buffer somewhere and never did get written into modem. Anyone got idea???

Re: modem problem

Emilie S. — Tue, 31 May 2005 17:58:45 GMT

Hi Justin:

Have you tried testing VISA communication in Measurement and Automation Explorer (MAX)? You can do this by going to your COM port under Ports which is under Devices and Interfaces. If you click on your COM port you can the click on Open VISA Session. Then on the Basic I/O tab you will execute a write, then a read if you application requires a read.

Please try this out.

Emilie S.
Applications Engineer
National Instruments

Re: modem problem

JUSTIN.YEH — Wed, 08 Jun 2005 02:16:37 GMT

Hi: Sorry for the late reply. I was out of town. My problem is lsoved, with some strange method.
I found if I set "flase" on the VISA config serial vi's "Enable termination char" and use code display instead of normal display on VISA write input (also add \r in the end).
It actually works. Can you tell me why I need to set "false"??

Best Regards

Justin

Re: modem problem

MichaelChaney — Wed, 08 Jun 2005 22:17:06 GMT

Hi Justin,

The "Enable Termination Char" and the "termination char" parameters specify what LabVIEW should be looking for when terminating a serial read. These parameters do not append any termination character to a serial write. The termination character that needs to be sent must be appended in your string to write, like you've done.

Thank you and have a great day.