Digital I/O

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Making my appliication detect changes on DI channels (NI-USB6501)


I would like to do the following with my NI-USB6501 boards: 

- I connect some sort of switch to a channel on the board that I configure as a  DI channel.
- Someone pushes the button (aka switch), 5 volts (for example) is generated on the channel

And this is wher 'im stuck: my applicaton needs to "sense" this change in voltage on the DI channel. I checked all the NIDAQMX functions, and searched the forums, but I didn't find a solution.

I guess my application will need to have an infinite loop in which it checks continuously for changes on the DI line. But: which NIDAQMX function will "sense" the change in voltage input ?

Thanks in advance for your help, once again,


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If you don't have a board that supports change detection (and yours does not), then as you said, you have to put the DAQmx Read in a loop and check for a change with your code. You don't mention which language you are using but surely there is a 'not equal' function. You have to use this to compare the last acquisition to the previous.
Message 2 of 3
Hi Dennis,

Thanks, this already helps me a lot. Now i know i should be "polling" for changes myself. Thanks a lot.

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