Multiple counters with same arm start trigger, no analog tasks available

[CodingMonkey]

Hi all,

I'm using the DAQmx 2022 Q3 C API, but basically the issue should be the very same with LabVIEW etc.
My hardware platform is a cDAQ-9181 chassis (1 slot) with a 9402 digital module.

I'm using all 4 digital channels to measure tacho signals (via DAQmxCreateCICountEdgesChan), which works perfectly well.
The issue I have is: The tasks are not synchronized. Basically, the start times of the measurements depend on the start times of the specific counter tasks, which start one after the other with a certain delay.

What I'm trying to do now is to have all four counters receive the same arm-start trigger signal, so that they start at exactly the same time.

As far as I can see, I don't have a suitable trigger signal available. I don't have an analog task where I could export the start trigger. I did import the "/dev/Ctr0ArmStartTrigger" (DAQmxSetDigEdgeArmStartTrigSrc, no error returned) on all other counters 1-3, and started counter 0 last, but that does not trigger the counters 1-3 at all.

Does anyone know how my problem could be solved?

BTW: If I switch to a larger chassis, say the cDAQ-9185, add an analog channel and use its start trigger, everything works fine. I just don't have an analog channel on the cDAQ-9181 with the 9402 module.

Thank you very much!

[Kevin_Price]

I'm exploring this using MAX, simulated devices, and the "Device Routes" tab associated with the chassis.

I see 2 options for you to try -- the DI start trigger and FreqOut.

1.  Config a short finite DI task using one of your DI channels.  Usually when a physical pin is shared for counter or DIO usage, that pin can be used for both a counter input task *and* a digital input task.   The internal signal ".../di/StartTrigger" should be routeable to be ased as your counters' Arm Start trigger and will assert when you start the DI task.

2. I don't think I've used FreqOut.  But it appears to be configurable as another output-only counter channel (with a much more restricted set of allowed output frequencies).  FreqOut also appears to be routeable for use as an Arm Start trigger.

-Kevin P