Garmin 18x GPS Puck

Oscilloclock models that synchronise time using an external GPS unit have been supplied with a Garmin 18x LVC GPS unit, colloquially known as a ‘puck‘.

The puck is wired with a high quality, robust connector for a secure connection to the Oscilloclock.

Does a Garmin 18x puck need ‘updates’?

No component of an Oscilloclock is perfectly future-proofed and completely immune to design flaws, software bugs, or unforeseen changes in global infrastructure.

The Garmin 18x is no exception, and there have been regular firmware updates through its lifetime so far, documented at Garmin’s Uploads & Downloads Page.

See our post Longevity, and the Garmin “puck” for a great read about one issue that occurred in 2019, when some older 18x devices failed to calculate the date correctly.

How to update your Garmin 18x

If you believe your puck needs a firmware update, or you just want to keep your gear up to date, there are two choices:

  1. Simply send the puck back to the Oscilloclock lab for a free upgrade. We’ll only charge for the return shipping! But in these days of reduced shipping options, the journey can be pricy.
  2. Purchase an optional Oscilloclock Garmin 18x USB Adapter. Plug your puck into a PC, download the latest firmware, and update it yourself – whenever you wish! This is especially useful if you have more than one puck (yes – there are wonderful folks who have purchased multiple Oscilloclocks)!

Introducing the Oscilloclock Garmin 18x USB Adapter

This adapter features both the small and large connectors used in Oscilloclock models crafted to date

The Oscilloclock Garmin 18x USB Adapter consists of a specially-programmed USB-to-serial interface unit and a custom adaptor cable with a jack that matches the connector on your GPS unit.

Just contact your friendly engineers at if you’d like to obtain one.

And read our 3-part series, Longevity, and the Garmin “puck” to see what was involved in its development!

Using the Adapter to upgrade your Garmin

Check the Prerequisites

  • 1 x Oscilloclock Garmin 18x USB Adapter, with a jack matching your puck’s connector.
  • 1 x Windows PC with a USB(-A) port, running a ‘modern’ version of Windows. Don’t even try this with a Windows version that is no longer supported, such as Windows XP or Windows 7. (Oscilloclocks may be designed to last, but Windows is not!)
  • 1 x User having “Administrator” login privilege on the PC.
  • A Good Deal of Patience!

Prepare the software…

  1. Download the latest version of the GPS 18x PC/LVC software.
    • Confirm that it has extracted a few files into the C:GarminGPS18x_PC_LVC folder.
  2. Download the latest version of the Garmin Sensor Configuration software (SNSRXCFG).
    • Search for “SNSRXCFG” in Google, or visit Garmin: SNSRXCFG Updates & Downloads
    • This is a single .exe file. Save it into the C:Garmin folder.
    • At this stage, your C:Garmin folder should like below:
  3. Is your monitor a “High DPI” monitor? If so, follow the next two instructions. If not, you can skip this. (If you have no clue what a “High DPI” monitor is, you probably don’t have one, and you can skip this.)
    1. Right-click the SNSRCFG_*.exe file in the C:Garmin folder, and select Properties.
      • Select the Compatibility tab and click “Change high DPI settings” button
      • Select “Override high DPI scaling behaviour” checkbox
      • Select “Application” in the dropdown, and click OK
    2. Follow the same procedure for the Updater.exe file located in the C:GarminGPS18x_PC_LVC folder.

Prepare the hardware…

  1. Plug the 4-pin rectangular black connector of the supplied GPS interface cable into your Garmin 18x USB Adapter unit.
    • Important: Be sure to orient the connector so that the RED wire aligns with the VCC pin. If you get this wrong you’ll get very frustrated later on. (But you won’t break anything…)
    • Equally important: Be sure to set the jumper connector (the small black plug you see at the left in the photo above) between the JP and 5V0 pins.
  2. Plug your Garmin 18x LVC puck into the jack at the other end of the interface cable.
  3. Plug the Garmin 18x USB Adapter unit into your PC, using the supplied USB cable.
  4. Do you know which COM port the adapter unit is represented by? If so, skip this step!
    1. Open Device Manager (either use Search or Windows key+X, then M).
    2. In the View menu, select Devices by Container.
    3. Locate the Garmin LVC Programmer entry, and expand it to show the device called “USB Serial Port (COMxx)“. Make a note of the port number – COMx. You’ll need it later!
  5. Have a few minutes’ rest. You made it this far!


All good so far? Let’s get into it.

If anything goes wrong at any time in this process, you may want to start the whole procedure all over again. I recommend that you close all applications, unplug the Adapter from your PC, and restart your PC. Just to be safe.

  1. Navigate into C:Garmin, right-click the SNSRXCFG_*.exe file, and click Run as administrator. This is absolutely critical!! You’ll fail miserably at a later step if you run this as a normal user.
  2. The Set Base Model to… window should appear. Select GPS 18x PC/LVC.
  3. Let’s tell the software how to communicate with your device:
    • In the Comm menu, select the Setup option.
    • Set the Serial Port to the COM port you identified earlier.
    • Set the Baud Rate to Manual, and select 4800 from the drop-down.
  4. Now we really get going! In Config menu, select Update Software.
  5. An information dialog will appear. It’s all illustrated below, so just press OK.
  6. The software will then try to connect to your GPS. After a few seconds, you should see:
    • If you see either of the below screens, there is some issue with the serial communication. Did you really set the correct COM port and 4800 baud in the Comm Setup screen earlier?
  7. A file chooser dialog will appear, asking to select the Region file. Navigate to C:GarminGPS18x_PC_LVC. You should see just one file available for selection. Select that file, and click Open.
    • If you see more than one file available for selection, that’s a bit odd. But try selecting one of them anyway. If there’s an error later in the process, you picked the wrong one – in that case, go back and select the other one. (Garmin’s instructions were a bit vague on this point…)
  8. Another file chooser dialog will appear, asking for the Updater. Navigate yet again to C:GarminGPS18x_PC_LVC. You should see the Updater.exe file. Select it and click Open.
  9. Now you should see the following screen appear. Set the Serial Port to the same COM port that you selected earlier. Leave the Baud Rate at its default value – no need to set this.
  10. The Updater software will try to connect to your GPS. If successful, you’ll see the below screen. You could note the current version of your puck’s firmware, just to satisfy your curiosity. But you won’t really need this information.
    • If you already have the latest version of the firmware installed, the following screen will appear. You still have the chance to proceed, or click No to abort the procedure.
  11. Almost there! The update will start and — hopefully — complete successfully!

Clean up your mess…

Hopefully everything was successful. Now you can clean up.

  1. Close all applications.
  2. Unplug the Adapter from your PC, and unplug the GPS puck from the interface cable.
  3. Plug the puck back into your Oscilloclock, and turn it on.
  4. Enjoy!

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