Output Multiple Digital IO with 2D N-Channel N-Sample

[tbriese]

I am new to LabView and the DAQmx tools, and I am trying to get a cDAQ-9178 with a NI 9403 card in it to output an exact copy of a digital waveform on all 32 IOs.  The attached VI only outputs the signal on IO0.  I am trying to use the DAQmx write with N channels and N samples.  The data into this module I believe is a 32x100 array with exact copies of the original waveform in each 100 samples.  The PCB for use with this module has already been designed and uses all 32 IO for a PWM so I can't simply use the PWM out of IO0 alone.

Any help on what I am doing wrong would be greatly appreciated.

- Thad

[NathanS]

Hi tbriese,

With digital I/O, the whole 32 bit port is a single "channel," and the wire terminals are "lines." This might be counter-intuitive if you've done analog I/O, because with analog, each wire terminal is one "channel."  So in your application, you have only one channel, but multiple samples. Hope that helps!

Regards,

[tbriese]

Nathan,

It doesn't make any sense to me since the DAQmx Create Channel (DO-Digital Output).vi can create channel(s) and I had the "line grouping" input set to one channel for each line which to me should create multiple channels.  In fact, if I had only a single channel of data (1D array) going into the N-chan, N-samp write block, I got an error on the size mismatch.

I did get this working.  I had to set the "line grouping" input to one channel for each line, remove the array builder that made my 1D array into a 2D array, and toggle a U32 from 0x00000000 to 0xFFFFFFFF.  Not a clean solution, but it worked.

The documentation for the DAQmx stuff is pretty poor on this point or it doesn't actually work for N-Channel N-Samp because I believe what I had should have worked.

- Thad