6259 digital waveform generation channel concerns

[PatrickH]

Hi.  I would like to generate digital waveforms on lines 0:7 of my USB 6259.  Currently I have the data as a 1D array of Digital waveforms.  This produces an error message that the number of channels in the task does not match the number in the list.  There seem to be other possible data formats, but I'm confused whether they are also possible.  Any comments on how to output the data shown in the control would be welcome.

One other query: when this VI runs, would the digital output be hardware timed, by the digital sample clock?

Thankyou all.

[Graziano]

Hi PatrickH,
   from datasheet I can see that NI 6259 has clocked DIO (32 Digital IO, up to 1 MHz).

   Sorry, but I'm unable to open your VI (I still have LV 7.1... ...) Anyway, I suggest to compare the two examples (found by NI example finder "Cont write Dig Port ...." and "Write Dig Channell....".  Are you using Port write or channel write?

   Hope I can help...

graziano

  

[PatrickH]

Well, I always start with the examples, and try to hack them.  I'm writing to 8 lines, addressing them as Dev1/port0/line0:7

So it's line output not port output

The example 'Write Dig Chan -Ext Clk' didn't seem to work at all, and I wondered if it was something to do with using the external clock.  If I can get hardware timing preicision with the internal clock then that's just fine, and I don't care about the external clock'.

The example 'Write Dig Chan - Int Clk, Dig Start' uses a digital start trigger, which I don't need.

What I presumably need is a simple 'Write Dig Chan - Int Clk' example.  Note that 'Write Dig Chan' example is no good: uses software timing and point by point updating.

[Graziano]

Hi PatrickH,
   of course, you've to cut examples to fit your needs (or to fit your hardware...).

   For example, you can eliminate the external clock, and configure it to be internal, (or, in some board, you set "as fast as possible", which means you doesn't have a precise HW clock...).

   I think you'd better use Port out, it simplyfies programing (it should, perhaps...).  Go deep in studying task creation/configuration, you can find many docs on NI site... and it's important to know exactly what is the "task" model of NI measurements.

   Let me know news......have a nice day!

graziano

[Graziano]

...about DAQ training, you should have installed on your PC the DAQmx-help, under --> programs--> NI --> NI-DAQ --> NI DAQmx help.

In particular, I suggest to take a look at Key NIDAQmx concepts , it helped me a lot at the very beginning... hope it's the same for you!

graziano

[Kevin_Price]

Re: External vs. Internal clock

The M-series boards do NOT provide a dedicated internal clock for digital input or output.  You must provide an "external" sample clock for the DO task.  You should think of this "external" as meaning "external to the DO task" but not necessarily "external to the board".   In other words, you don't necessarily need to physically wire up a signal from the outside world.  You *can* use signals that are internal to the M-series board.

Typical choices would be to "tap into" the sample clock from an AI task, an AO task, or to use a board-generated counter pulsetrain.  I'm sure you can find more info around here with search terms like "DO sample clock", "correlated DIO".   To get you started, link 1, link 2, link 3...

Can't offer help about the digital waveforms.  I've tinkered just a little bit and not found any compelling reason to bother.  I just use raw arrays of Booleans or unsigned ints.  (Not trying to argue you away from digital waveforms if you find them useful, just explaining why I can't help with them.)

-Kevin P.