I Can't Detect Any Changes on My Digital Input Line

Updated Nov 14, 2018

Reported In


  • Digital I/O Device
  • PXI Digital I/O Module

Issue Details

I'm working with a DAQ Card containing DIO ports.
When I configure an acquisition, or use the test panel on NI-MAX to acquire a value on one of the DIO line, I can't see any changes, although the signal is changing.


There can be multiple reason to face this behavior.
Please verify these following :
  • Some DIO cards can be configured by port, and other by line. This mean that you can't have on a same port, inputs and outputs (for example if P0 is configured as input, P0.2 can't be an output). Please check the user manual for this information.
  • Some cards are in pull-up configuration, while others are in pull-down configuration. This mean that the reference pin should be connected either to GND, +5/3.3V or be in tristate mode (this information can be found in the device specifications)
  • The cable you are using may be not compatible with your card
  • Verify that the DAQmx Read function is not throwing an error
  • Verify with another device (for example a DMM) that you're external hardware is providing the signal without any distortion or attenuation


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