GPS card


The GPS card is a BC637PCIe card provided and supported by Microsemi (used to be Symmetricom) until 2029.

The card is a “Time and Frequency Processor” (TFP). Synchronizes its 10 MHz oscillator to input reference
(GPS antenna)
It Outputs time signal to SEB10
  • Saved for all data events
  • Used for matching CRT to TPC data
  • Gives +5V to antenna

The GPS Antenna on the roof of LArTF

Connected to PCIe card in SEB10 in LArTF computer room

There's a Spare/test antenna on the roof of DAB, Spare card in LArTF computer room test stand


Occasionally the TFP (PCIe card) firmware will need to be updated because of a bug (this has only happened twice so far)
The update will be available on Microsemi’s website (see below for details on how to access the website)
Usually accompanied by a field service bulletin - the DAQ expert mailing list is subscribed to email notifications when these bulletins come out, but they are also available on the website in case we missed it (again, see below on this page for details about how to access the website).

To do the update:
  • Take out the GPS PCIe card from seb10, find a windows computer with a PCIe slot (most windows desktops have one)
    • Last time this needed to be done, Linda Bagby helped us find a Windows computer - ended up finding one at DAB, "in the annex by the hurricane deck" (with the help of Geoff Savage, who co-ordinates things at DAB)
    • In general, Linda Bagby is the person to contact when you need parts for something like this!
  • Plug in PCIe card and download patch software and executable to install onto the card, install the software, and then take the card out and back over to LArTF.

LED status indicator:

  • Off: No power
  • Red: No valid reference
  • Orange: Valid reference but not locked
  • Solid green: Freerun mode
  • Blinking green: Locked to timing reference

Status bits:

  • Tracking:
    1. 0: Locked to Selected reference
    2. Flywheeling (using internal
  • Phase
    1. 0: Synchronized within 2 us of timing reference
    2. 1: Greater than 2 us
  • Frequency
    1. 0: Oscillator frequency offset small timing reference
    2. 1: Large offset (unstable)

Monitoring the Status bits:

Monitored in slow controls monitor
  • Major alarm when status is not 0
  • Also major alarm when GPS time and the PPS (server) time are different
  • Ganglia status only updates during a run!
    Note: The GPS status in the slow controls monitor only updates during a run, If a new problem occurs, or if a problem has been fixed, we won’t know unless we are in a run.

Monitoring by ssh into SEB10 to check directly -
NOTE : DO NOT WHILE TAKING DATA it causes the time output to drift, which will cause a major alarm and will have to restart the run
run the command:


to get:

Status: Doing position fixes
Error: 1
Time format: 1 Binary
Time: 2016-04-08T19:11:05.334726+00:00
Unixtime code: 1460142665.334726
Time status: 0
Local-GPS difference: 0.000022 s

run the command:


to get:

 Symmetricom - TT & M
 bc635/637PCIe-V2 Configurator Version 3.0
 1. Read Current Time (Press enter to return to menu)
 2. Read Event Time (Press enter to return to menu)
 3. Set Current Time
 4. Set Current Year
 5. Set Strobe Time
 6. Program Control Register
 7. Program Leap Event Seconds
 8. Select Time Format
 9. Select Operational Mode
 0. Exit the Program...........................................................
 Select Option: 1
Binary Time: 04/08/2016 19:11:17.4769589 Status: 0
Binary Time: 04/08/2016 19:11:17.4873723 Status: 0
Binary Time: 04/08/2016 19:11:17.4976740 Status: 0
Binary Time: 04/08/2016 19:11:17.5079504 Status: 0

General trouble shooting - for more detailed cases, go to DAQ Expert Troubleshooting

1. Restart the run - this will usually fix if the time has drifted out of sync
2. Reboot SEB10 - this will usually fix if the GPS comes up in status 7 after being powered down
3. Contact Microsemi - they have been the cause and solution of a few of our biggest problems

Checking the Microsemi website

Software updates and announcements are released on the Microsemi website if a bug is found or a new feature released. We have signed up the DAQ mailing list to a mailing list that should inform us when an update is released, but you can always check on the website to see if we have missed something. The username is kwoodruff, and you can get the password in the "projects" tab of the ECL.

When you go to the website and log in you will see a page that looks like this:

Click on the link bc637PCIe under "My Products/Applications". That takes you to a page that looks like this:

At the top of the page, in the section labelled "Field Service Bulletins", you can find information about recent updates and check if there is anything that we missed. Towards the bottom of the page you can also see software updates.

Another thing that can be found on this page is the manual for the GPS card, which is very useful for debugging. To save you going to the webpage just for that, we have also attached the manual to this wiki page (see below).

Manual for our GPS card


Wes: the most likely problem the GPS rollover could cause would be in the comparisons of NTP time to GPS time - to do with the later merging with the spill information and having the right time stamp for that