USB-6501 On is Off and Off is On

[Phil_]

Hi,

I have a USB-6501.

When I send a True value to the DAQmx write digital VI the signal from the hardware switches off, and when I wire a false value the hardware switches on.

The same happens with an input. Shorting between pin and ground causes the output of the DAQmx read to read false, and with no connection it gives a true value.

A colleague has the same problem with the 6501, but not with his PCI DAQ card.

This is somewhat counterintuitive when programming. Is there a way to reverse this behaviour? (other than just remembering to add in a not gate)

Simple test VI attached.

[apok]

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@Phil_ wrote:

Hi,

I have a USB-6501.

When I send a True value to the DAQmx write digital VI the signal from the hardware switches off, and when I wire a false value the hardware switches on.

The same happens with an input. Shorting between pin and ground causes the output of the DAQmx read to read false, and with no connection it gives a true value.

A colleague has the same problem with the 6501, but not with his PCI DAQ card.

This is somewhat counterintuitive when programming. Is there a way to reverse this behaviour? (other than just remembering to add in a not gate)

Simple test VI attached.

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well, ive never seen that type of style done that way...are you trying to save room?its probably why you are having trouble....

Spoiler

[Phil_]

Hi apok,

I have just tried your recomendation, and functionally there is no change.

Any other ideas?

(also, yes, trying to keep it neat)

[apok]

hmmm, works on my end? and i even tried your vi...perplexed

[Phil_]

All of the inputs appear high in MAX when running the Test Panels section too...

[apok]

thats because there is a pull up connected....

The default configuration of the USB-6501 OEM DIO ports is open-drain,allowing 5 V operation, with an onboard 4.7 k  pull-up resistor.

[Phil_]

Tested with a different usb-6501 on a different machine. Same problem...

If yours is working ok Apok, then this really is wierd.

Would you care to elaborate on the above Apok?

My electronics knowledge is minimal

[apok · Accepted solution]

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@Phil_ wrote:

Tested with a different usb-6501 on a different machine. Same problem...

If yours is working ok Apok, then this really is wierd.

Would you care to elaborate on the above Apok?

My electronics knowledge is minimal

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your IO is connected to a 4.7Kohm resistor that is also connected to 5Vdc....transistor is off, outputs pulls up to 5Vdc level and transistor on...output pulls down to near gnd,considering diode drop of emitter