APFI for Digital Input Clock Source?

[SuperSnake428]

I am using the NI-6289 to acquire 16 channels of digital inputs. My custom PCB connects directly to Connector 1 of this card and the output of the oscillator is wired to APFI1. I should have checked the signal routes first and clearly would have seen that APFI1 cannot be used as the clock source. Unfortunately, to my knowledge there are no other signals on this connector that can be used as the clock source for digital inputs. Is this correct? I could easily make a jumper if there was another signal that could be used.

Any gurus out there have any ideas how I can get this to work?! I also have a NI-6733 card on the board but I don't have an RTSI cable as of now (ordered but would like to get this working ASAP).

Thanks,

Drew

[MarkGrot]

There's nothing on connector 1 that you can use to import a sample clock.  You need a PFI line and those are all on connector 0.  RTSI would work too.

Are you using your clock for any other subsystem?  Can you use a pulse train generated by a counter on the board for a clock?  Otherwise you're going to need to wire up to a PFI line.

[SuperSnake428]

I am using Counter0 to divide down the clock but it doesn't look like the input of that counter can be APFI1 either. 

[MarkGrot]

Right, you can't use APFI lines to import a clock.  You need to use RTSI or a PFI line from connector 0.  I don't know what your clock signal is, but am curious if using a counter to generate a similar signal would be good enough for you to get up and running until you can get a RTSI cable or figure out a way to wire to a PFI line.

[John_P1]

If you're not using Analog Input, you could configure an AI Start Trigger on the APFI line.  This will route the APFI line to the internal comparitor--the resulting signal is called the Analog Comparison Event and can be used as a clock for your digital task.  See the below diagram from the M Series User Manual:

Even if you are using AI, if you don't mind starting it based off of this clock signal then this could still be an option.  It's not exactly straightforward, but it might be easier than reworking your custom PCB.

Best Regards,

[stilly32]

Just to tack on another option: You can use change detection on one of the Port 0 lines on Connector 1 to generate your clock. Not sure what API you're using but if in LabVIEW I'd start with the "Read Dig Chan-Change Detection.vi" shipping example. Just set the clock line to be either a Rising Edge line or Falling Edge line (or both if you want to sample on the rising an falling edge) and leave the other blank.

Cheers,

Andrew S