digital ouput synchronized with AI and AO

[labmaster]

Hi,

I want to out a digital signal as a irregular trigger signal.

One of counter was used in sample clock channel. and reference clock was used to synchronized among AI, AO, and function generator.

Anyway, when I add digital channel in the same way of AO and AI, I met an error in the property node of "reference clock" and "Start Digital Edge.vi"

Would you kindly guide me which part should be corrected?

Labmaster.

[John_P1]

Hi Labmaster,

I'm assuming you're on an M Series DAQ device (622x, 625x, or 628x).  The error you are receiving (-200452) indicates that timing/triggering is not supported for this task.  On M Series devices, the digital lines do not have their own timing/triggering circuitry.  You cannot provide a reference clock or start trigger to a digital output task on an M Series, rather you provide an external sample clock.

If you want to provide external triggering/timebase signals, you may do so as a part of the counter task that is being used to generate the digital output.  Simply trigger the counter output off of the external signal and use a timebase that is synchronized with your other tasks (if all tasks are on the same device this shouldn't be necessary).

As a side note, our X Series DAQ Devices (63xx) do support triggering on all subsystems (AI, AO, DI, DO, Counters) and do not require an external sample clock for digital lines.

Best Regards,

John

[labmaster]

Thank you. I forgot to give the model: PXI-6124 (S series).

While I was waiting for the reply, I read its manual.

Does it mean that the digital channel is started with AI, AO, or Counter in the same time automatically?

In my case, all functions were used a counter signal as a sample clock.

But I have a independent trigger siganl in AI and AO. 

>

NI 6124 devices do not have an independent DI or DO Start

Trigger for digital waveform acquisition or generation. To trigger a DI or

DO operation, first select a signal to be the source of DI Sample Clock or

DO Sample Clock. Then, generate a trigger that initiates pulses on the

source signal. The method for generating this trigger depends on which

signal is the source of DI Sample Clock or DO Sample Clock

> 

For example, consider the case where you are using AI Sample Clock as the

source of DI Sample Clock. To initiate pulses on AI Sample Clock (and

therefore on DI Sample Clock), you use AI Start Trigger to trigger the start

of an AI operation. The AI Start Trigger causes the non-isolated

DAQ-STC2 S Series device to begin generating AI Sample clock pulses,

which in turn generates DI Sample clock pulses, as shown in Figure 6-2.

[John_P1]

Hi labmaster,

I forgot about the S Series for a moment, this one should behave in the same way as I mentioned above (the 6124 uses the STC-II chip like M Series).

It sounds like you want separate triggers for each of the three tasks.  If this is correct, then I would use the counter to generate the clock for the digital line (you can trigger the counter), and use the on-board clocks for AI and AO which will accept their own trigger lines. 

The digital channel will be started whenever it is armed (in software) and will update based off of the clock you are giving it.  For this reason, if you trigger the clock you are effectively triggering the start of your digital generation (since the first sample isn't generated until the first clock tick).  You just need to make sure to start the digital output task in software before the trigger signal comes in otherwise you could miss sample clock ticks.

If you provide more info about what you need to do I can give more specific information about how I would go about it.

-John