Hello Forum,
I'm just getting confused now, because I've tried hundreds ways to solve this little requirement on a 6254:
- Reading a digital edge which have to be filtered and using this event to trigger a digital port scan on P0 -
Sounds easy, doesn't it ?
Whatever solution I've tried, it always comes up with an error popup telling me, that I'm doing something wrong.
Now I start to think there is no way to do it.
Is there anybody who can tell me whether this is possible or not for sure ?
I have wasted so much time !
What I have recognized very early (help files say this very clearly) is that digital filtering on a 6254 is only supported
on "counter inputs". So, I started to realize that:
DAQmxErrChk (DAQmxCreateCICountEdgesChan(Task, "/Dev1/Ctr0", "", DAQmx_Val_Rising, 1, DAQmx_Val_CountDown));
DAQmxErrChk (DAQmxSetCICountEdgesTerm(Task, "/Dev1/Ctr0", "/Dev1/PFI5"));
Because, I don't want to poll on the result, I installed an event handler:
DAQmxErrChk (DAQmxRegisterSignalEvent(Task,DAQmx_Val_CounterOutputEvent,0,(DAQmxSignalEventCallbackPtr) SampleCallback,eventrec));
The help says, "Counter Output Event" is raised whenever "Terminal Count" reaches zero. This is why I let it count back from 1 to 0.
But, it doesn't work, telling me something about sample clocks to use.
This is just the simplest way I've tried. Out of this many trials end up the same.
What I've tried so far:
- the digital filtering workaround example given by NI as VI (translated into Labwindows)
-> no edge detection on PFI possible
- trying to react on the counter output/input with edge detection method
- using a sample clock on the counter -> only external clocks supported
- generating a pulse train using Ctr1
-> DAQmx Create Timing Source create an invalid source because the specified
Sample Timing Type is not supported when the signal is Sample Clock -200800
- using the counter output as a trigger for immediate port scan within 1 task
Now, I'm out of ideas.
