no SCAN_Demux in daqmx ?

[josswern]

I'm currently trying to port an existing cvi-app to daqmx (because the new pci6250 boards are no longer supported in trad. ni-daq) and just wondering if there is no more SCAN_Demux function.
with traditional ni-daq, I just used :

        Err = SCAN_Start(Board, buffer, Nch * Nsamp, Timebase, Interval, 0, 0);
        SCAN_Demux(buffer, Nch * Nsamp,Nch, 0);

to de-multiplex the acquired data - now there doesn't seem to exist something similar in daqmx ???
(daqmx seems to be a big mess, btw.)

[cdk52]

Hi.

You could try the TransposeData() function from Programmer's Toolbox.

Regards,
Colin.

[cdk52]

...or (probably the better option), call DAQmxReadAnalogF64() or DAQmxReadBinaryXXX(), with the fillmode parameter set to DAQmx_Val_GroupByChannel.

[josswern]

ok, thanks.
I'll check this out (I already saw 'DAQmx_Val_GroupByChannel' - option, but wasn't sure if this would do the job).

[Graziano]

Hi!

    DAQmx_Val_GroupByChannel is a property of acquisition, so you can group data as you want in one function, instead of calling 2 functions, one for scan, one for demux!

    I've spent some days in converting projects to newer versions of DAQ, and let me say that I've found DAQmx more powerful, and flexible.  There's only a need for comprehension of DAQmx new concepts (e.g., in old daq you hadn't tasks....).

  Good luck!

graziano

[josswern]

you're right, Graziano,
I think the concept with 'tasks' is the key.
at a first glance, I got the impression, that one would have to create a specific task for _each_ measurment via some obscure wizzard or thelike,
which would have been a real pain.
now, tasks can be created programmatically, according to the needs of the planned measurment, and that's the way to go.

[josswern]

ok,
now figured out how to proceed with daqmx, I face a totally strange problem:
the measurments taken with daqmx, even in MAX 4.0 - appear to be crap.
my board is a pci-mio16-e4, with an sc2040 s/h attached.
it _does_ work with traditional daq in MAX test-panel, as shown in the screenshot tr-daq.gif (correct voltage shown, stable),
but with daqmx, voltage just floats continuosly awy, until limit of card reached (daq-mx.gif) ???!!!
is this a major bug in daqmx (version 8.0, trad daq=7.3) ??
(please, anyone from NI, look at this..)

[Graziano]

Hi!

   I think it depends upon channel configuration.  But I'm not practical with german (even if I'm learning....), and I'm not used with DAQ assistant.  I suggest you to change some parameters in your channel configuration, in test panel, depending on your board; Moreover, it would be great you manually start a task, and configure it, so you can list all functions you use to accomplish this.

  BTW, I refer to "Terminal configuration" property of DAQmx Create AI voltage channel function.  I hope the problem is not due to the fact that your card is a little bit old.....

graziano

[josswern]

thanks for reply, Graziano,
I'll check again my configuration, but I'm sure I used _the same_ config. for test with traditional daq AND daqmx.
I used daq-assistant just to verify, because my task gave wrong results.
maybe it is really related to the fact that I use the (rather old) pci-mio16, but then it is a major bug in daqmx driver
(which is supposed to give correct results for _all_ supported cards).
I'll also check with a newer pci6250 tomorrow.

[Graziano]

Hi!

   PCI 625x boards work very well with new daqmx, but it was with a PCI 6251 that I encountered the same problem you reported! That's why I suggested to look carefully to chennel configuration.

   Sometimes, when you pass from traditional DAQ to DAQmx you may miss some detail, that was my fault!

   Anyway, if you want, show me the code lines regarding task/channel creation-configuration, both in traditional and DAQmx, if you want!

   Good luck for tomorrow!

graziano.