limite nel buffer dati dovuto a sistema operativo?

[Cristina]

Buon di'!
Ho un problema con il passaggio da un pc con sistema operativo Windows 2000 ad un'altro con XP. In sostanza volevo copiare i miei programmi (scritti in LabWindows) sul nuovo pc (dotato quindi di una nuova scheda Gpib) e tutto funziona bene fino a quando, fatte le misure, voglio scaricare i dati dal multimetro. Alla mia richiesta di lettura del buffer (circa 3900 byte) vengon scaricati solo 2000 byte. Questo sia da programma che volendo interrompere il programma, usando Measurement Studio: ibrd indica le letture fino al 2000 esimo byte e da' time out error. Ho provato ad usare lo Spy per vedere se ci fosse qualche problema con i settaggi dello strumento ma sembra di no. Non riesco a capire se e' la scheda mal configurata o se il sistema operativo pone qualche limite alla cominicazione, visto che per un numero inferiore di letture il problema nn si pone (meno di 2000byte da leggere). Grazie per eventuali suggerimenti.
Cordiali saluti,
Cristina Knapic

[MarcoL]

Hi Cristina,

if i understand you have problems during the reading of the buffer of your device. I suppose that the problem is not the OS that you are using but the setting of the timeout of the reading function. If you post me the code error that appear during the buffer reading I can search if there is in database any document that can help you to configure the device. If is possible I need also to know what kind of device you are using.

Thanks,

Marco Lencioni

Application Engiineer

National Instruments Italy

[Cristina]

Hi and thanks!!
I'm not sure the problem was OS but I suppose that because I tried to set the new GPIB (mounted on a new pc with Xp) like the one is working on the old pc with a Windows 2000.
The timeouts are both set to 10 s .... I will check again .....
The problem is that some data came from my multimeter (Keithley 2000) but it stop automatically after 2000 bytes transferred.
The error is a timeout error but i don't understand what it means.
Do you need the code ?
Thank you very much,
Cristina

[MarcoL]

Hi Cristina,

I studied your problem and I found some documents that talk about a similar problem. take a look to the link below:

http://forums.ni.com/ni/board/message?board.id=140&message.id=5947

http://forums.ni.com/ni/board/message?board.id=140&message.id=10586&requireLogin=False

These two Discussion Forum refer to other two documents:

The Effect of UART FIFO Sizes on Serial Application Performance.

http://digital.ni.com/public.nsf/websearch/2D5F972CD550BBC386256F0B005E9A63?OpenDocument

Why Do I Get Buffer Overflows with My Serial Port When Using VISA with Flow Control?

http://digital.ni.com/public.nsf/websearch/D776A9D834B132AB86256ED2004E18EF?OpenDocument

In particular the last one helps you to modify the setting for the buffer size. I think that finally the problem is related with the change of OS (from Windows 2000 to Windows XP)

Take a look to all the documentation and let me know if the problem is solved.

Marco Lencioni