NETMF hardware monitor for the Trimble Thunderbolt GPS disciplined clock.
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Shield Changed board font to vector Apr 22, 2014
TrimbleMonitor (Fez Lemur) Add support for LCD backlight brightness #1 Feb 18, 2018
TrimbleMonitor (Netduino)
TrimbleMonitor (Netduno Plus) Add support for LCD backlight brightness #1 Feb 18, 2018
.gitignore Added support for FEZ Lemur Aug 10, 2017
Example-LCD.png Example LCD Image Feb 5, 2014 Added a link for the direct download to VS2013. Nov 28, 2017
Trimble Monitor Instructions v1.0 (obsolete).docx Updated the documentation Nov 4, 2017
Trimble Monitor Instructions v1.1.docx No longer show the survey as 0% complete when no survey is in progress. Nov 7, 2017
TrimbleMonitor.sln Added support for FEZ Lemur Aug 10, 2017

ATTENTION: If you are already running this project you must update to at least v1.0.4 which corrects the problem where the date rolls back to 1997. The Trimble Thunderbolt will have stopped reporting the correct time from July 30th 2017 for any hardware/software which reads its data unless it is aware of the rollover.

If you don't know how to use GitHub and just want to download the latest development code, visit You can always redownload the latest version with this link. If you want an official releases, click the releases link.

Thunderbolt Monitor is a stand-alone microprocessor-controlled LCD specifically for the Trimble Thunderbolt disciplined clock, providing a comprehensive indication of the Thunderbolt's status, modes, and alarm conditions written in C# (NETMF).

Data packets appearing on Thunderbolt's serial port are in Trimble Standard Interface Protocol (TSIP), not NMEA sentences, so this display will not work with NMEA GPS units, such as Trimble's Jupiter or any other GPS.

Ideal for amateur radio applications, Thunderbolt Display shows Time Of Day (UTC) to assist with logging contacts, and also calculates Maidenhead Grid Locator Square from the current latitude and longitude.

The software runs on a Netduino or GHI FEZ Lemur which is a .NET version of the popular Arduino platform. It also requires a shield to make connecting it up to the microcontroller much cleaner. I have designed the shield to be compatible with both Netduino and Arduino in case someone wants to write code for the other platform.

There are three projects in this repo.

  • TrimbleMonitor (Fez Lemur) – Basic monitor for the GHI FEZ Lemur (No NTP)
  • TrimbleMonitor (Netduino) – Basic monitor for any Netduino 1, 2, 3 (No NTP)
  • TrimbleMonitor (Netduno Plus) – Monitor with NTP support for a Netduino 2+ / 3 Ethernet / 3 WiFi

The board must be running .NET Micro Framework 4.3. You should use Visual Studio 2013 for this project. More information can be found within the instructions document.

Blog posts can be found at

Contains an NTP server implementation which allows you to sync your computer clock with the Trimble Thunderbolt.

You can now buy the shield as a PCB from

The Netduino and GHI FEZ Lemur are available from a few places but consistently seem to be in stock at Mouser.

I do not have a version of the code for Arduino but I'm happy to include it in this repo if you wanted to write it.