Denuo GPS Retrofit Board

Here is another quick post about some progress I've made toward developing a retrofit board for the Lucent KS-24361 REF-0.

Denuo GPS Retrofit Board for the KS-24361 REF-0

The Denuo GPS is a drop-in retrofit board for the REF-0. It uses the u-blox NEO-6M GPS module. There is a microcontroller on the board that translates the UBX serial messages from the u-blox to the Oncore format for the REF-0. The microcontroller also replicates control functionality of the REF-1, in that it automatically sends the appropriate messages with the correct timing for the GPSDO to operate. This enables standalone operation. While the NEO-6M is not a timing GPS, the board is still able to send sawtooth correction and other timing-related information.

The board is a significant step up from my previous prototyping efforts. It installs just like an Oncore GPS would in a REF-1. Power and signaling are handled through the 10-pin header used by a real Oncore. There are a small number of modifications that need to be made to the REF-0 to enable this, such as mounting standoffs and removing two SMD jumpers. The normal antenna mounting location is not present on a REF-0, so I opted for a u.FL connector and a pigtail to the outside. I think the finished install looks pretty nice. What do you think?

The Denuo GPS board mounted inside of a REF-0.

The board also has some neat features that are enabled by the modern GPS receiver. Sensitivity is hugely improved compared to the Oncore. Time to first fix is several seconds instead of several minutes. Also, the board breaks out the USB connector of the u-blox GPS. I can now monitor GPS status and tweak settings using the free u-center application.

So you might be thinking, "Where's the beef?" Or rather, where's the timing GPS module? The REF-0 is a GPSDO after all, and the original Oncore GPS was of course made for timing. Don't worry, that version of the board is in the works too.

A sneak peek at the Tria GPS Timing Module.

So that's it! I have a REF-0 with the Denuo GPS humming away in a quiet corner. Over the next few weeks, I'll be collecting data on the performance of the GPSDO with this retrofit board.

More to come.

Thanks for reading!

- Dan W.