error when trying to use DO as "open collector" on PXI-6602

[uli82*]

When I try to configure a DO of my PXI-6602 as "open collector" I receive the error -200452 ("Measurements: Specified property is not supported by the device or is not applicable to the task."). This is completely mysterious to me since the PXI-6602 should have this feature and my code (see attachment) is practically identical to any of the numerous examples for this topic. Am I overlooking anything really stupid? (LV 8.5, PXI-8145RT) Cheers, uli

[muks]

Please see this thread

[Brad_K · Accepted solution]

Hi uli82*,

The error message is correct. The PXI-6602 does not support the DO.OutputDriveType property. If you want to set the PXI-6602's DIO lines to a high-impedance state, use the DO.Tristate property or create a digital input channel.

Configuring a DIO line's drive type as open collector would cause writing a 0 to drive the line to 0 V and would cause writing a 1 to tristate the line. If this is the behavior you want, you'll have to emulate it using the DO.Tristate property.

Brad

[uli82*]

Hey Brad,

thanks for you help. I think what you are suggesting should work. As I get it in the tristate both of the push-pull-MOSFETS of the DO are open, so the DO goes to a high impedance state. However, I cannot set this property while the task is running. And then I would have to worry about the state of this output before I set the property and so on. Here is my preferred solution. One can just connect the DO to the gate of a MOSFET, the drain to ground and then use the source as the output. voilà.

uli


P.S. Am I the only one that is misinterpreting the NI specs for these PXI cards that say "Output Current Flow Sinking, Sourcing"

[Brad_K]

Hi uli,

Did you try setting DO.Tristate while the task is running? There are a few DAQmx devices that do not support setting DO.Tristate while the task is running, but I don't think that the PXI-6602 is among them. I don't have an actual 6602 installed but with a simulated PXI-6602 and DAQmx 8.9, setting DO.Tristate while the task is running does not error.

Using external hardware is perfectly fine, and should also work for timing I/O (whereas using DO.Tristate would only work for single-point digital I/O).

I don't see the text that you quoted in the NI 660x Specifications, so I don't know what context it was in, and apparently it has been reworded since then. Note that devices that support open collector output say "open collector (open-drain)" in their specifications; for an example, see the NI USB-6008/6009 User Guide and Specifications.

Brad