Serial Console Out with cRIO Appears Blank and Frozen

Updated Apr 6, 2023

Reported In


  • CompactRIO Controller

Operating System

  • NI Linux Real-Time

Issue Details

I am trying to connect to the serial console output of my cRIO. When I launch PuTTY and attempt to connect to the target with the Serial connection type, the session screen launches, but does up blank and frozen and I cannot type anything in.


1. Check baud rate settings.

Ensure settings of COM port in MAX are configured according to the RS-232 console out settings of the cRIO port. For example, you can find these settings in the cRIO-9035 manual in a table on 5 in the Enable Console Out section.

Additionally, ensure that the speed setting on PuTTY or another client you may be using is set to match the same console out settings. For example, cRIO-9035 uses baud rate 115,200 bps.

2. Serial Cable

If behavior persists, you may have an issue with cabling. Serial cables and male-male adapters may be null modem/crossover or straight through. Using the wrong kind of cable results in signals being written and read through unexpected pins, which usually manifests as timeout errors on serial read operations. When connecting multiple cables of different connector types, it can be difficult to determine ultimately which pins signals are being sent and received on (TXD and RXD pins). Serial loopback tests can be performed to determine which pins the TXD and RXD signals are being transmitted on.

3. Restart into safe mode.

Boot the controller into user-directed safe mode. The console should display messages as the target boots.