How to use DMA in linux?

[mkko]

Hi,

This is not exactly an area of my expertise, but I'd need to output analog signal with an M Series card in linux. I'm using the NI DAQmx Base driver and apparently it does not have any direct support for DMA access. As I understood, the NI DAQmx driver would have a support for DMA, but the newest version of driver for linux (openSUSE) is from 2005. With current implementation the output is not very steady as there are some other mandatory processes on the background and the driver already seems to be using nearly all of the CPU time. Any help would really be appreciated. Thanks in advance.

-- mikko

[JoeFriedchicken]

Hi mikko,

DAQmx Base does support DMA, but only for analog input (which obviously doesn't match your application's needs).

However, I don't believe you will need the DDK to support DMA for analog output on your hardware: installing DAQmx 8.0 is possible on newer Linux distributions, and one user in particular shared his procedure [1]. His instructions mention using NI-KAL 1.6, but my recommendation is to use the latest [2]. National Instruments hasn't tested DAQmx 8.0 on these newer distributions, so I can't say what the driver's performance would be in your situation. I can say, though, that I've installed DAQmx 8.0 on openSUSE 10.3 successfully and was able to use the shipping examples for an internal demonstration.

If you encounter problems, please reply and tell me which hardware you want to use and which Linux distribution you're currently using. It will be much easier to install DAQmx 8.0 on a newer release of a supported distribution (like SUSE [3]) than a on an unsupported distribution.

[1] Installing LabVIEW 8.2.1 with DAQmx 8.0 on Suse 10.3 for Linux.
http://forums.ni.com/ni/board/message?board.id=170&view=by_date_ascending&message.id=331638#M331638

[2] NI-KAL for Linux
http://joule.ni.com/nidu/cds/fn/p/sb/navsRel/lang/en?q=ni-kal

[3] National Instruments and Linux: Frequently Asked Questions
http://www.ni.com/linux/support.htm#1

[JoeFriedchicken]

Just a small update -- DAQmx 8.0.1 is now available for Linux. From the download page [1]: 

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The following main features were added in NI-DAQmx 8.0.1:

• NI LabVIEW 8.6, 8.5, and 8.2 support in addition to LabVIEW 8.0
• Support for Mandriva 2008 and 2007, and openSUSE 10.3 and 11.0

---

[1] DAQmx 8.0.1

http://joule.ni.com/nidu/cds/view/p/id/1194/lang/en