DAQ_DB_Half_ready problem while double buffered AI

[ed austin]

Hi guys,
I really hope you can help me here because I'm stumped. I'm trying to continuously aquire data from my Lab-pc card within Lab Windows 5 using double buffering. I'm using the 'DAQ_DB_Half_Ready' function to check for ready half-buffers. The very first time a half buffer is ready, the function returns the required output, and I can read my half buffer with the transfer function. The DAQ_DB_Half_Ready function never signals a ready half buffer again, no matter how many times the aquisition loops around the buffer.
Even the NI-DAQ example program fails with the same symptoms!!

Anyone get any ideas??

cheers

Ed

[bman]

Ed

If you are using the Lab-PC-1200, I have seen this problem before. The only way around it is to set the data transfer mode to use interrupts instead of DMA. This is done with the Set_DAQ_Device_Info function with the infoType to ND_DATA_XFER_MODE_AI and the infoValue to ND_INTERRUPTS. This is not a problem with any of the newer E-Series boards. Let me know if setting the transfer mode to interrupts does not work.

Brian

[ed austin]

Thanks Brian. I'm using a Lab-PC+ board ATM, but maybe upgrading to a 1200 board later, so your comments are very useful. In the end, I found the problem could be sorted by upgrading the version on NI-DAQ from 6.5.1 to 6.6.0.
As a side issue I discovered that labwindows 5.0.1 is incompatible with nidaq 6.9.2 - in fact it won't even start properly with this version of ni-daq. I think this should be documented in the Ni-Daw 6.9.2 release notes - it would have saved me a whole lot of heart ache!

Thanks again for your response

ed