It s a project where I have created a NTP Stratum 1 server with 100Mbps Ethernet port and Alide GT-U7 GPS module that gets time from satelites and works as a stratum 0 source.

Chrony configuration

The file chrony.conf is my example from /etc/chrony/chrony.conf. It has the configuration for allowing RFC1918 (all private networks) and to use GT-U7 GPS module.

Boot configuration

After attaching everything correctly the config.txt file in /boot/firmware/config.txt needs to be edited to enable dtoverlay dwc2 module and UART for GT-U7, then SPI and dtoverlay w5500 module for the 100Mbps port. Lastly GPIO 18 is specified as PPS pin by loading dtoverlay pps-gpio module and specifying GPIO18 as the PPS source.

Telegraf configuration

The gpsdMeasurement.py file goes to /etc/telegraf and inputs.conf and outputs.conf go to /etc/telegraf/telegraf.d/.

The only file that needs to be edited is outputs.conf because it has the destinations to which metrics will be sent. In my case it was InfluxDBv2

EasyEDA folder

There is a schematic to how connect the Raspberry Pi Zero 2W with W5500 and GT-U7 modules. There is also a 5V regulator but it can be ommited if a stable 5V source is provided (like USB).

influxMeasurements file

There is a description of each metric that is collected by gpsdMeasurement.py script

dashboard.json file

It has a Dashboard for Grafana that visualizes the data collected

Price

Total price should be around 15 Euro for the GPS module, 10 Euro for the GPS antenna, 4 Euro for a SD card, around 4 Euro on Aliexpress for the W5500 module and 21 Euro for a Raspberry Pi Zero 2 W.

In total the price should come to approximately 50 Euro excluding soldering station, solder, cables, power supply (can be whatever USB-A power plug as long as it gives 5V 1A).

Some pictures

How the server looks

Here is a picture of my current "in production" NTP server. It is not the prettiest but it works. I do not have a 3D printer so I can not print a nice enclousre for it. I have also decided to add additional heatsinks for the WiFI chip, CPU, SD card, and the W5500 chip (it was getting pretty hot to touch).

How the Dashboard looks

Here is how the Dashboard looks in Grafana. Note that GPS Data section repeats on both images.

Sources and Inspirations

My initial inspiration for setting up that local NTP server was a post by spookyghost on NetworkProfile.org. It was a basis for how and where to connect the GT-U7 module.

Second port that inspired me when it came to Grafana, telegraf and that Python measurement script was by shrunbr on blog.shrunbr.dev. It gave me a good overview on how telegraf works and how inputs and outputs.conf is configured. The same goes for my Dashboard in Grafana. Shrunbr's dashboard was my startpoint, even though I had to remap all the values.