6211 usb: Digital input with digital edge triggering possible? External reset for counter available?

[acevedo]

Hello,

I have two questions:

1) I want to adquire a digital signal using a NI USB 6211. I want to read one sample each time that a digital signal has a rising edge.

Is it possible with the NI USB 6211? If yes, do I have to route a external signal or is there the possibility to have an internal routing (similar as with a PCI 6221).

2) I want to adquire two digital signals 90º phase shifted with a single counter. I also want to use a third signal to reset this counter. Is this possible with the NI USB 6211?

Thank you in advance,

Best regards,

Eugenio

[RamonaL]

Hi Eugenio,

You can use also with the USB-6211 device a other signal as clock (you digital signal). So as you can see in MAX under the tab "Device Routes", which routes you already have. Yellow means, that you can use the route, but through a subsystem. For example: The PFI5-7 can be routed through Counter 1. If you use a route like that, you wont be able to use the counter 1 for anything else.

And to point 2 I am not sure, what you really want. Normally you can use only one counter for one signal and not one counter for two signals. Maybe you can post the singal or explain a little bit better what you want.

Regards,
RMathews

[acevedo]

Hello again and thank you for your answer regarding point 1).

About point 2), what I want to make is to measure two digital pulses trains (with 90 degrees offset) using one counter, and also have the possibility to reset the counter. I made something similar with the NI 6221 PCI board, using these signals:

- "CTR 1 A" for pulse train 1

- "CTR 1 B" for pulse train 2

- "CTR 0 Z" for the reset signal

My question is if it the same is possible with the NI USB 6211

Thank you in advance

[RamonaL]

Hi,

ok, this a little bit strange. Normally you use that only for encoders.  A counts the signal and B ist just there to tell if A should count up or down.
And when you use the CRT 0 Z, this should reset the CRT 0 and not CRT 1.

Can you maybe just describe how your signal is, what it looks like, where it comes from and what you want to do.

Thanks,
RMathews

[acevedo]

Hello,

I should have written "CTR 0", this was only a typing error.

I will use to measure an encoder, exactly.

With your last answer everything is clear now.

Thank you very much.

[stilly32]

Eugenio,

Let me try to clear things up. First off, Digital I/O on the USB 6211 is completely software timed - it will not acquire or generate on a HW edge regardless of whether the clock is internal or external. You can take a clock signal in and route it to AI, AO, or the counters, but DIO does not support using a clock. This is different from the USB self powered devices (like the USB-6221 and USB 625x) which support correlated digital I/O - which means you can acquire/generate on a hardware edge.

For your second, the 6211 does support encoder measurements with it's counters - so you should not have any issues with that aspect.

Hope this helps,

Andrew S

Message Edited by stilly32 on 10-30-2007 10:39 AM