simultaneous generate and acquire of digital ouptut in USB-6501

[thames]

Hi

From previous postings its known that simulataneous generate and acquire is possible with analog signals (N-samples or continuous mode sampling)

Im using "sweep" execution to "write value" at a USB-6501 DAQ channel and this permits only "1 sample (on demand)" (others give errors)

With this setup is it possible to simultaneously generate and acquire the same channel

Thames

[sahpe]

Hello Thames,

It was never possible to have simultaneous reads and writes on the same channel in any device. This is always implemented on different channels. It is however possible to do single points in either direction sequentially and quite fast, with minimal latency between them, and you can have a look at the attached LabVIEW code if you have LabVIEW installed. Albeit simple, it achieves a Digital In and then Out, but still sequentially. This is the same as you have achieved in SignalExpress, and the main reason why you get errors if you choose Finite or Continuous modes (referring to a resource that is already in use?) is because you cannot have a single wire to "move" data in two directions at the same time.

Why do you believe you need to have an input and an output on the same channel at the same time? This would be physically impossible anyway, but if you explain exactly what you are trying to achieve and what you have connected up to your 6501 then we can probably help you find another way around it.

Kind Regards,

Michael S.
Applications Engineer
NI UK & Ireland

[thames]

Hi Michael

I am trying to send data across one channel for N clock cycles - i use "generate" step here, after Nth clock cycle the same channel will recieve some digital data from external components - i use an "acquire" step here.

I set up a generate step and an acquire step on the same channel - it gave error for using the same channel in two different tasks which are not "sequential"

I have modified the setup - I use two channels now - line1 and line2 ,but short them externally. Now I can do generate step on line 1 and acquire step on line2. This works fine.

I have attached the signal express project

Thames

[sahpe]

Hello Thames,

Thanks for the clarification, it makes much more sense now.

The USB-6501 is a low-cost digital IO device that cannot achieve hardware timing, and therefore is not able to manage the Finite or Continuous mode. So you can use sequences or step dependencies, and Conditional Repeats to achieve multiple cycles. Your implementation seems fine and I am glad it works as you needed it to now!

Thanks for getting back to us, all the best with the rest of your application!

Kind Regards,

Michael S.
Applications Engineer
NI UK & Ireland