Hi nkambe,
First I would like to confirm how you are testing this operation. When testing a digital card, it is always a good idea to use Measurement and Automation Explorer and set up test panels to confirm that the board is reading correctly. You can set the direction as input or output depending on the port and then drive the output line high or low. If you have the lines connected correctly from one port to the next, you should be able to read on the input ports, what you are outputting in test panels.
There is a
knowledgebase that describes connecting an external pull-up resistor to a DIO line. However, this document specifies this value should equal the value of the internal pull-up resistor from the DPULL pin on the card. This other
knowledgebase shows those internal values. Your card though, seems to not use internal resistors in order to driver the line since the DPULL pin is not on the pinout. I also couldn't find any information in the documentation about these values.
First try testing your device and the connections thouroughly because this should not be an issue. Then you can look into different resistor values based on what the other cards use and see if those correlate. Hopefully this will help!
Regards,
Vanessa L.
Applications Engineer
National Instruments