digital acquisition

[cyrilng]

Hi
i have to acquire continuously digital inputs with M series multifunction DAQ.
i've seen examples in the ni example finder, using external clock.
is there a solution that doesn't need external clock?
thanks

[daviddelebecque]

Hi,

The M Series of National Instruments products includes the capability to synchronize digital input and output with other operations. "Correlated Digital IO" enables the coupling of buffered digital tasks with the analog, counter/timer, or external clocks. The Digital I/O subsystem does not have its own internal clock source, and therefore, an external signal or clock from another subsystem on the board must be provided - thus correlating the digital data to this signal.

There is no other way, regards

David D. - Applications Engineer - NI France

[cyrilng]

In fact i don't know if i really need a continuous digital acquisition.
i have a digital sensor ( 0 or 5v) and i have to detect when it passes from 0 to 5V
how should i proceed?

[daviddelebecque]

The best way will be to operate "change detection" but this is not supported by M series. (only certains DIO boards)

You do not need to use external clock just to read the state of a digital line. You just have to put a while structure timed by software. You do not need especially that timing comes from the board. Look at the examples in CVI to help you.

Regards,

David D.