08-29-2008 06:26 AM
All I have simple VI I am using to Transmit various different messages over a USB COM port (using FTDI chipset) to a device then carry out a subsequent RX.
Some messages do not result in a reply back from my device and in this case I do not experience a problem, however when I use a message (e.g. send a status request) that causes my device to give a reply I get the "Connection for the given session has been lost" error whilst attempting the RX.
My RX is achieved by using a using a VISA get property node to get the no. of received bytes and then feed this to a visa read. It seems the error occurs at the visa read. It seems inconsistent as occasionaly the error is not generated on the first TX & RX cycle, or during the first few.
Although I have read some similar posts on here concerning this there are a few gaps which I need to fill to help me resolve the problem. I am using LV 7.1 on winxp service pack 2.
1) How can I find out my version of VISA as i understand an out of date version could be the problem
2) I have tried the documented trick of using the VISA set I/O buffer size but am usure of what mask value should be used if it is failing on RX
Any help much appreciated.
08-29-2008 08:20 AM
I am now using ft245rl chip as the usb controller.I faced a lot of problems wih communication initially.
Please go throught he following stes
08-29-2008 08:21 AM
08-29-2008 08:26 AM
There is a Knowledge Base article on this error code, but it was for Win-2000. Don't know if it applies to Win-XP..
The article mentions VISA 2.5 which is a rather old version. Which VISA version are you using?
08-29-2008 08:36 AM
I am using the FT232BM.
08-29-2008 08:58 AM
Is it neccessary to take the D2xx route to get round this problem? I am using the VCP drivers so that I can treat my device like a virtual com port.
This has worked well for me for ages when I have used the same FTDI device with an RS485 interface,
The only difference here is that I am using an IBIS interface which runs at a slower baud rate and has different data bit/stop/start/parity settings and a different electrical interface, I cants why this would start generating these errors.
Can anyone inform me how ro acertain what version of VISA i have please.
08-29-2008 12:02 PM - edited 08-29-2008 12:03 PM
Here are a couple of ways to verify which VISA version you have.
(Preferred): If you have MAX (Measurement & Automation Explorer), simply open the program, expland the "software" tree and look at NI-VISA, the version number should appear in the box on the right. In my case, I have VISA 4.2.
(not necessarily accurate): START menu, All Programs, go into National Instruments> VISA > Documentation> NI-VISA Read ME
It will describe which VISA version you have.. Example, I get:
© 1995–2007 National Instruments Corporation. All rights reserved.
09-01-2008 04:36 AM - edited 09-01-2008 04:36 AM
Hi ATE Man,
I hope your well.
I am looking into your issue.
Firstly, I would like to repeat the request to know what version of NI-VISA your using, on face value your issue seems to be in the driver layer.
I have been looking on the FTDI website and have found a link for LabVIEW examples (maybe try these incase its your code that is an issue). Also, you will need to use/install FTDI drivers also.
Please response with an update/more information.
09-10-2008 03:40 AM
Hi ATE Man,
I was just wondering how things were coming along with your application and I am just posting to check if everything went ok and whether the problem was resolved as I have not heard back from you. If you have any further questions on this issue, please respond.
06-26-2012 02:23 PM
I am currently using LabVIEW 2010 and TestStand 4.2 to test a series of UUTs. The UUTs contain a FTDI FT232R chip to convert a USB bus into a serial COM port. I am using VISA mapping to connect to the COM port, along with a windows registry edit to 'lock' the COM port locations on the test PC (preventing Windows7 from adding a new COM port for each new UUT tested). So far, this part works fine.
After each test, I need to disconnect the first UUT then connect the next UUT. The resource is found and mapped into the appropriate COM port location. Unfortunately, when I re-run the test, the error message "-1073807194: VISA: (Hex 0xBFFF00A6) The connection for the given session has been lost." The only way I have been able to continue testing is to exit and restart LabVIEW. This test needs to be made fully automatic for production line purposes.
Is there a way in LabVIEW to re-acquire the VISA resources without having to exit and restart? Do I have to use the d2xx drivers to talk to the FTDI chip instead of the VISA drivers?