The swiss makes of GPS receiver chips and modules u-blox has (among others), a line of so-called timing GPS modules.

The main difference of such modules compared to the standard modules is their ability to output arbitrary GPS-derived clock
signals anywhere between 0.25 Hz and 10 MHz.

This allows such modules to be used in a varity of high-precision timing applications where a simpler/traditional approach using
regular 1PPS outputs is not sufficient.

The Osmocom project has developed an evaluation / development board for the u-blox LEA-6T timing module. Like all other
Osmocom projects, it is fully open source, i.e. schematics and layout files are freely available.

photograph of the assembled osmo-lea6t-gps board

Electrical Design

Schematics and Layout

The most up-to-date versions of the schematics and layout files can be found in the projects git repository which can be
browsed at or cloned like this:

$ git clone

For your convenience, PDF files are also attached as ublox-lea6-test.pdf and ublox-lea6-test_brd.pdf.

Major components

How to use

You can connect to it using one of the Osmocom-style serial cables (3.3V UART on 2.5mm audio jack) or using USB. You will get
a serial port that can speak either NMEA or the proprietary UBX protocol.

The full protocol is specified in the u-blox 6 protocol specifiation.

Where to buy

You can have the PCB etched anywhere you'd like, using the layout data we have provided. Most of the components
are available via distributors like Digikey. Only the LEA-6T module has to be obtained through an u-blox distributor.

sysmocom used to be selling fully assembled boards in their webshop but this service is discontinued!


osmo-lea6t-gps was designed by Sylvain Munaut. Prototype manufacturing and testing was performed by Harald Welte of sysmocom.

Files (3)
osmo-lea6t_small.jpg View osmo-lea6t_small.jpg 168 KB photograph of the assembled osmo-lea6t-gps board laforge, 05/20/2012 10:03 AM
ublox-lea6-test.pdf View ublox-lea6-test.pdf 50.2 KB Schematics of Version 1 laforge, 05/20/2012 10:26 AM
ublox-lea6-test_brd.pdf View ublox-lea6-test_brd.pdf 33.3 KB Component placement of version 1 laforge, 05/20/2012 10:26 AM

Updated by laforge over 1 year ago · 12 revisions

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