Sampling multiple digital channels, each channel with different clock

[leofur]

Hi,

I'm using NI PCIe-6536B to sample digital data, the data is a single bit (sigma-delta). I'm trying to sample multiple devices, all the devices has almost the same clock, but I can't synchronize the clocks. Is it possible to sample few channels, each channel with it's own clock? I've tried with change detection, but I can't creat two tasks with one device.

any help will be appriciated, 

Thnks,

Leo.

[Artem.SPb]

You can only configure multiple frequencies. To do this, you should configure the task with several channels: 1-2-1-3 In this case, the frequency of 1st channel twice bigger.

[Kevin_Price]

I don't know that specific board, but a common restriction for many NI data acq boards is to support only one hardware-timed Digital Input task at a time.  (Also true for each of AI, AO, DO.)

I think you'll just have to capture all the data at some fixed rate, bearing in mind that some of the transitions may be captured nearly 1 sample later than they actually occurred.

There'd be a possibility to try change detection across all the DI in a single task, but there are some quirks there as well.  If the changes are happening faster than the change detection timing can handle, they won't all initiate their own sample.  More than one bit may have changed between consecutive samples.  Other quirks are possible when bit changes are nearly but not quite truly simultaneous.

-Kevin P