Use cases

• Synchronize the RT system clock to an external time source (Internet Time Service, or ITS)
• Include in the RT start-up VI to keep the system clock always up to date (RT has no built-in real-time clock to preserve the correct time/date across power cycles)

Features

• Communicates with the NIST Internet Time Service (ITS) via a TCP/IP connection
• Opens a TCP/IP connection to the “Daytime Protocol” on port 13
• Reads the returned 51-character string, and parses it for the time and date information
• Validates the returned string by checking that the “server health” digit is at least 1 and that the label “UTC(NIST)” magic string is present before actually adjusting the RT system time
• Packaged as a subVI (“sync clock to NIST time.vi”) that you can easily incorporate into your own project

Keep in mind

• RT requires a network connection capable of reaching the Internet
• Consult a time zone selector service such as the TWiki.org Timezone Selector to obtain your time zone, a required input for the LabVIEW “Set Time” VI that adjusts the RT system time
• Adjust the “century number” input should you be running this code after the 21st century

LabVIEW block diagram elements

Locate these elements with "Quick Drop" (press Ctrl+Space and start typing the name); click on an icon to see more sample code that uses that element:

Example code

• Install the Academic RIO Device software set add-on called “NI System Configuration” to enable the functionality of the “Set Time” VI which adjusts the system time
• Enable the Academic RIO Device wireless connection to a consumer-grade wireless router with an Internet connection (press the Device wireless button if connection was established earlier)
• Run the “check internet access (tcp)” VI to confirm that the Device can reach the Internet (the “Internet OK” indicator lights up).
• Download and unpack the rt_time-sync-to-nist.zip (for use with NI myRIO 1900) or the NIELVISIII-rt_time-sync-to-nist.zip (for use with NI ELVIS III) archive, and then double-click the ".lvproj" file to open the project. NOTE: This project was written for a NI myRIO 1900 or NI ELVIS III connected by USBLAN at IP address 172.22.11.2. If you are using a different IP address or another Academic RIO Device (Example: NI myRIO 1950 or NI RIO Control Module) do the following:
  • If using the NI myRIO 1950 or NI RIO Control Module start with the NI myRIO 1900 Archive.
  • Different IP address: Right-click on the "NI myRIO 1900" Device, choose "Properties", and then enter the new IP address
  • Different device:
    • Right-click on the top of the project hierarchy, select "New Targets and Devices", keep the "Existing target or device" option, and then find and select your particular device
    • Select all of the components under the "NI myRIO 1900" device: click the first one and then shift+click the last one
    • Drag the selected components to the new device
    • Right-click the "NI myRIO 1900" device and select "Remove from project"
• Open and run “RT Main” and observe the following:
  • The “time before sync” indicator displays the system time before an attempt is made to contact the NIST time server; this value is likely quite far from the correct time depending on the “System Start Time” stored on your Device (to see this value, use NI MAX or browse to http://172.22.11.2 (requires USBLAN connection) to look at the “System Settings” tab for your device)
  • The “time after sync” shows the updated time after contacting the time server
  • An inactive “sync OK” front-panel LED indicates that the synchronization process failed, possibly due to an unavailable Internet connection, inability to contact the time server, or garbled return string

Expected results

Developer walk-through

For more information

1. NIST Internet Time Service (ITS) (http://www.nist.gov/pml/div688/grp40/its.cfm)
   See the "Daytime Protocol" section for complete details on the returned character string.
   
2. NIST Internet Time Servers (http://tf.nist.gov/tf-cgi/servers.cgi)
   A list of available time servers.
   

Related content

Tags:

• networking
• IP address
• TCP
• NIST
• system clock

Targets:

• RT

LabVIEW VIs and block diagram elements:

• TCP Open Connection
• TCP Close Connection
• TCP Read
• Set Time
• Date-Time To Seconds
• Get Date-Time In Seconds
• Scan From String