Digital I/O

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DIO - Single Line vs Port (U8) Write

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I have a wierd situation:


I am using a NI 6509 Digital I/O card, with 4x digital outputs connected to P2.3 thru P2.6.


1. I setup a task to write to these lines using a group of global virtual channels - all done in MAX.

2. I have used this task/setup on previous occassions with good success.

3. Yesterday it stopped working.

4. Now the old task does not work.

5. I have reset the device (and PC) on multiple occassions

6. I created a "NEW" task which writes to the whole port at once (i.e. U8) and I can measure the output voltage changing fine (using  DMM) when I run this VI.

7. So I know that the digital outputs are working... but when I try the old task again, it still does not work.


Can anyone please tell me of a reason why this behaviour might occur. I know that some DIO products can do port read/writes only.


I am suspicious that the device (our product) the DIO card is connected to might have been accidentally connected in such a way that there were two competing output signals/pins connected to the same wire.


Does this sound like a hardware fault?


Any suggestions muchly appreciated.



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Accepted by topic author sammy346

Don't bother, I found the fault - the external hardware had been changed without me knowing.

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