What is it?

It's a GPS receiver that outputs a fixed frequency that is locked to the UTC time standard from the GPS network. It is delivered with software that by default sets it to 1MHz but this can be changed by issuing a command on the serial port.

When the GPS has received a fix it will output the RF signal on its RF Out connector as a 0 to 3V Square wave. The output signal is very accurate in frequency so it can be used to calibrate or to PLL lock Oscillators etc. Although the primary function is to output this accurate frequency on the SMA connector - you can also read the position coordinates on the serial port once it is locked.

The module can be powered by any voltage in the range 3,3V to 5V and takes about 50-70mA of current. An GPS antenna must be connected to the GPS Antenna port, you can run the module with an indoors GPS antenna that you put next to a window but for best performance use an outdoors antenna with a clear view of the sky.

The Yellow LED will blink while it is acquiring a fix and will lit continuously when a fix have been calculated by the GPS module.

The IDC connector is for power input, serial in/out and for RF Output and fix signal, see schematic. Source code available on Github.

Why did you make it?

To be used as a calibration source for my oscillators

What makes it special?

It is very easy to use. Just plug in a GPS antenna and provide power and it will output it's calibration signal after a few seconds. When moved to a new location it can take a bout 2 minutes to get a fix but after the initial fix it is much faster, usually only 2-20 seconds after power on as the fix is stored in battery backuped RAM. All programming of the GPS module is performed at power on by the Arduino Pro Mini that is included.

Since firmware 1.05 there is a feature that makes it possible to enter serial passtrough mode. This is intended to run in conjunction with the uBlox uCenter software and makes it possible to access all the features of the Neo-6 GPS module that is on board. Passtrough mode can be entered by issuing a serial command or by shorting pin 7 & 8 on connector J3 before startup.