Labview issues with Multiple Serial Ports

[cyerdon]

I am building a station to test a product which requires a total of 96 serial ports to communicate with the products under test. I have been encountering a problem with the cpu being very heavily taxed once all 96 ports are initialized using the VISA create vi. Essentially, with task manager open, you can watch the cpu cycles increase as each VISA instrument (each serial port) is initialized. By the time the 96'th port is initialized, the cpu reaches 100% and the computer is working as hard as it can. The computer is a pretty decent DELL Optiplex 3.0GHz with 2GB RAM, so im not entirely sure that it is related the the computers ability. How do I initialize this large quantity of serial ports without taking up all of my computers resources? Is there a better solution to initializing the serial ports or perhaps another method? Are there any known problems with VISA creating this many references? Any help would be helpful. Thanks.

[mikeporter]

Boy! 96 serial ports? It sounds like you are saying that even with no serial port traffic the CPU is maxing out? This makes a certain amount of sense, in that the OS is constantly monitoring the serial ports to see if any data has come in that needs to be buffered. What sort of serial devices are you using? Can you distribute some of the serial IO into devices that have their own built-in intelligence? For example there are devices that have multiple serial ports and interface to the PC over ethernet. What speeds do you need from the ports?

Mike..

[unclebump]

Here is one with 32 serial ports on one ethernet connection.

http://www.digi.com/products/model.jsp?lid=EN&pgid=114&pfid=49&mtid=189&amtid=189&pm=Y

Here is one with 128 ports on one card.

http://www.digi.com/products/serialcards/acceleportcx.jsp

Message Edited by unclebump on 01-04-2008 12:49 AM

[Graziano]

Hi!
   96 serial ports.... I'd like to see a picture of that system!

   Are you using all 96 port at the same time? Can you open/clos ports upon your needs? it's quite normal that 96 ports overload the PC.  Using Ethernet to serial adapters is a good solution, just check how important is jitter for your application!

graziano

[cyerdon]

Thanks for your advice guys! As for the configuration, all 96 serial ports are being used at the same time, so opening/closing is not really an option. The devices I am using are the USB16-RM USB to serial adapters shown here at http://www.usbgear.com/computer_cable_details.cfm?sku=USB-16COM-RM&cats=199&catid=493%2C494%2C474%2C...

I was under the impression that they would do what I would need seeing they are EEPROM programmable as well as have large receive/transfer buffers.

I have considered using a separate PC to handle the ports but am a bit reserved on doing so as the station is already getting pretty mammoth.

Anyone have any idea what I can do to make the computer able to handle this heavy load?

[Ben]

It's been some time since I touched a machine with that many serial ports, and back then it was one of the front-ends (VAX 6800?) for the SEI Super-Computer.

What little I can offer...

1) Are you sure you are using a USB 2.0 port on your PC?

2) Are your devices USB 2.0 ?

3) Did the manufactuer provide any type of utility you can use to determine if the CPU load is do to their driver or is it due to VISA?

4) Can you post the code so we can do a quick review to make sure there isn't a simple explanation?

5) Are you you using the latest and greatest version of VISA?

Ben

Message Edited by Ben on 01-04-2008 08:08 AM

[Rimasaurus]

Hi,

NI-VISA supports a maximum of 256 serial ports.  As long as you're not using an older version of NI-VISA, then NI-VISA will support 96 serial ports.

Regards,

Rima

[Graziano]

Hi Rima,
   here the problem seems not to be the number of supported ports, but performance... anyway, I didn't knew that number, so thanks!

graziano

[cyerdon]

I am currently running VISA version 4.2 which is the latest.  Also, the devices are USB 2.0 and are set to use UART vs. FIFO as I have been told that UART requires less CPU power to communicate with the USB Devices. Any Other Suggestions?