shorter digital output pulses

[Baboon]

Hi all,

I'm using the output pins of the 7344 - board. Depending on the movement of a xy - stage (controlled by the motion controller) I'd like to trigger a laser pulse. Unfortunately the output pulse has a length of about 20 ms and so I have to decrease the speed of my stage rapidly (otherwise the pulses will overlap).

Is there a way to control the length of these pulses? I'm using the library "flex_set_port".

Thanks in advance for your help.

Best regards,

Martin

[Jochen]

If you start and stop the pulse by software under Windows you will never be able to determine the length of the pulse exactly due to non deterministic operating system latencies.
Things will improve if you run the pulse generation in an onboard on the 7344 as there is a deterministic real-time operating system running on it.

If you need to start the pulse at a specified position the most accurate method would be using the breakpoint functionality of the board to trigger an external counter device like the PCI-6601 to generate a pulse with an adjustable length. The PCI-7344 and the PCI-6601 can be connected internally with a simple ribbon cable to share synchronization signals via the RTSI bus
without the need of external signal connections.

Best regards,

Jochen Klier
National Instruments Germany

[Baboon]

Thanks for the fast response.

Is it also possible to trigger the laser directly from the breakpoint output? I think a pulse length of about 10 µs shout be enough.

Best regards,

Martin

[Jochen]

In general yes but with the 7344 the breakpoint stays active after each occurrence until you reset or rearm it in your program. And this is - again - software timed so the situation doesn't change much this way.

[Buechsenschuetz]

Again, maybe a hardware solution is possible... With a simple circuit using the 74LS123 you can generate pulses with almost any length desired. You can supply this circuit from the +5V output of the 7344.

[Baboon]

Is it not possible to use the toggle - action (in the modulo mode) to set and reset the breakpoints?

Can I also use a 6024E board instead of the 6601? What exactly will the DAQ-board do after getting a signal? I still have problems to understand the reason for the DAQ - board.

Thanks in advance for your help.