How to generate a pulse waveform 90 deg phas shifted with respect to a pulse generated using a counter in PXI 6070E daq card ?

[Gops]

Hi
I ma using 6070E daq. I am generating a infinite pulse train using one of the counters. I want to generate another pulse train which should 90 degress phase shifted with respect to the previsously generated pulse. How to implement this using the counters in the DAQ card.

[rgharrison]

Hi Gops,

Although this functionality is present on NI-TIO counter/timer chips (NI-660x boards) by use of an initial delay within the counters (could program a delay equal to 90 degree phase shift) this is not available on DAQ-STC chips (E Series boards). This is because DAQ-STC counters do not support an initial delay in pulse train generation mode (driver doesn't support it).

The only way I see this happening is if you use the frequency generator on the E Series to generate your first pulse train (output on the freq_out pin) and use your two main counters to generate 1) a delayed pulse which will gate 2) your second counter which is a pulse train of the same frequency. To get the phase correct, your delay of the pulse should be equal to 1/4 of the period
of your pulse train period and should be gated/triggered by one of the rising edges of your frequency generator pulse train. The actual pulse width of this single pulse should be made as large as possible (or should toggle the output). I have included a couple good references to get you started. Hope that helps. Have a good day.

How Can I Generate Two Pulse Trains without Using Both Counters on My E-series Data Acquisition Board?
http://digital.ni.com/public.nsf/websearch/129541C85CEEDDBF86256ADF005C4409?OpenDocument

Using the General Purpose Counter (GPCTR) on the Data Acquisition (DAQ) Device as a Digital Line
http://digital.ni.com/public.nsf/websearch/B8A49A4E33F38AB686256B610061DC6D?OpenDocument

Ron
Applications Engineering
National Instruments

[Gops]

Hi
Thanks for your suggesstion.
I have few doubts wiht respect to your suggesstion,

1. Is the output waveform from the freq out is programmable?

2. I couldnt follow the second part of your answer, (where you have mentioned using one counter to gate the other counter) Can you please elaborate on this ?

Thanking you
Gopal

[rgharrison]

Hi Gopal,

1) yes the frequency generator is programmable. You have 2 timbebases (10MHz and 100kHz) and you can divide down by any integer between 1-16. Those are the only frequencies you can use.

2) The way counters work is that you can apply a gate signal to the counter which will cutoff the output. Therefore, you can have a second counter generating a pulse train of an equivalent frequency to the frequency generator (fout) but you don't want it to start immediately. You want it to start only after a short delay (equivalent to a 90d phase). Therefore, you need to "gate" or prevent the output on this counter for that small delay period of time. The way you can do this is by using a second counter to create a delayed pulse. You would
connect the output of that counter to the gate of your pulse train function. That way, during the delay period of the pulse, you won't be outputing your pulse train yet. When the pulse (high-time) of your pulse reaches the gate, then your pulse train will start generating its pulse train (which is consequently delayed by the amount of delay used in the single delayed pulse counter). Since you don't want your pulse to go back low, you will have to turn off or clear your pulse counter while it is high. That way the signal on the gate will remain high forever.

Your better solution is to use a PCI-660x card to perform this action. You will have more counters which will give you a greater range of frequencies to choose from and you will have more accurate timing of the signals.

Anyway, hope that clears things up. Have a good day.

Ron