Using the SMB Connector for Digital I/O or Drift Compensation on cRIO-901x and 9074 Controllers

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Hardware: CompactRIO>>Controllers>>cRIO-9012, CompactRIO>>Controllers>>cRIO-9014

Problem:
The Operating Instructions manual for cRIO-9012/9014/9074 controllers states the following:

"The software that supports GPS drift-correction and other digital I/O through the SMB connector was not available when this manual was published. Please contact National Instruments for more information."

How can I use the SMB connector on these controllers?

Solution:

You can use the SMB connector of cRIO-9012/9014/9074 controllers to connect a digital device to the controller. For example, if you connect the pulse-per-second (PPS) output of a GPS device to the SMB connector of a cRIO-9012/9014/9074 , you can use the GPS device to correct for drift of the system clock of the controller. You can also use the SMB connector as a general purpose digital I/O line.

Using the SMB Pin as General Purpose Digital I/O

To use the SMB pin as a general purpose digital I/O line, download the set of VIs attached below in the file 901x SMB Pin.zip. This zipped directory contains 4 VIs to read, write, set, and get the SMB pin mode.

Using the SMB Pin for GPS drift-correction

To use the SMB pin for GPS drift-correction, add the following lines to the ni-rt.ini file for the controller. You will need to FTP this file onto a Windows machine, make the changes, and FTP the modified file back to the controller. After updating the ni-rt.ini file, the cRIO-901x controller will automatically implement the GPS drift-correct based on the PPS input.

[Time Sync]
source.rtc.enable=True
source.dio.enable = True
source_priority=dio;rtc;
source.dio.hz = 1.0
You can also set the expected frequency of the input. The default is 1.0 Hz. For example, If 2 Hz is the expected frequency, change the last line to source.dio.hz = 2.0.

Note: If the PPS signal is lost or the error is greater than 10% off from the expected frequency, then the drift-correction measurements will not be used to correct the clock time on the Embedded Controller.