Error -1073807252 during a VISA read.

[jefska]

Error -1073807252 during a VISA read.

I'm performing a VISA read operation after a write and if I run a small script I get a warning 1073676294, VISA:  (Hex 0x3FFF0006) The number of bytes transferred is equal to the requested input count. More data might be available.

When I run a larger script I get the error VISA:  (Hex 0xBFFF006C) An overrun error occurred during transfer. A character was not read from the hardware before the next character arrived.

I need to run very large scripts in my application so hopefully there is a solution using the VISA functions.

Jeff

[Matt_S.]

The solution to this is to use hardware or software flow control. This will prevent the instrument or what ever you're talking to from sending additional data until you've read everything from the buffer. Another solution is to read from the buffer faster. You can do that by decreasing delays in loops that are reading from that serial port.

I hope this was helpful. If you need any clarification, just let me know.

Regards,
Matt S.

[jefska]

Thanks Matt for the reply and I'll make note of the solutions proposed.

I found the problem and it was not in my labview program but rather it was a fault message in the response from the hardware that labview is interfacing with.  The response from the hardware was in a continuous loop therefore the read buffer could not keep up.

Thanks again,

Jeff

[julesjay]

Jefska have you resolve your problem because I've got exactly the same?

I'm currently using labview RT 8.2 on PXI-8196.  I receive a status via RS232. I 'm using the byte at port.vi and when there are 156 bytes at port I read it to get them. Sometimes the count return is 12 or 18 or anything...

My application worked fine. Then I 've changed my host computer and installed LV RT 8.2 on it. Since that , I've got an intermittent error -1073807252  VISA (hex 0xBFFF00EC).  I've made a lot of tests to solve it but I failed. I don't understand where it could be from!!

VISA read.vi is in asynchronous mode  -----      My port settings are : Com1   9600 baud   8 data bits  no parity   1 stop bit   no flow control.

I've seen in LV RT 8.2, there is a new advanced tab in MAX under 8196 / COM1 where I can select FIFO buffer. I've tried with or without it's the same problem. 

As I said before I 've tried to correct the error   but I didn't succed in!!!!

So any Idea???

Message Edité par julesjay le 01-08-2007 10:47 AM

[jefska]

It’s been quite awhile since this was an issue for me.  I assume you tried what Matt suggested.  The only thing that comes to mind is to take the return count from the VISA write and multiply that by some factor as an input to a Timeout(Wait function) before the VISA read and increase the multiplier if the read buffer does not get the entire byte count.  Also the Basic Serial Write and Read.vi in LV examples might be of help.

ATB,

Jefska

[julesjay]

I've already tried to increase  of write, and wait a time before read but it still doesn't work.

As I use a byte at port vi, I think there is no need to wait because these byte a ready to be read.

[julesjay]

And I cannot use flow control because of the instrument I communiucate with!!!!

[julesjay]

It might be usefull to say that if I didn't use DMA FIFO between FPGA and RT there isn't any error!!!!  STRANGE????

[bburress]

Hey julesjay,
    It seems that the real-time controller is too busy servicing the DMA transfers and does not have enough time to handle the serial transmission, and therefore the VISA buffer overflows.  KB 3BE87GW3 discusses why this occurs, and possible solutions for it.  Basically, the buffer either needs to be read faster, or the buffer size increased.

[julesjay]

Brian,

My former computer runs LV 8.0.1. So I've upgrade it on LV 8.2 and the same error occured. I've donwgrade it to 8.0.1 again and there isn't error anymore. Then I've donwgrade NI-SERIAL RT 2.5.6 on PXI chassis and the error occured. I've re-installed NI-SERIAL RT 3.0 and no error.

I think that maybe NI-SERIAL RT is in cause. 

On the new computer I've just uninstall NI-SERIAL 3.1 form my 8.2 version and replace it by  NI-SERIAL 3.0..... Wait and see....

I'll give you the result tomorrow!!

Thanks.