https://github.com/geerlingguy/time-pi
Raspberry Pi stratum 1 PTP and NTP timeserver configuration.
https://github.com/geerlingguy/time-pi
gps ntp ptp raspberry-pi time time-server
Last synced: 4 months ago
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Raspberry Pi stratum 1 PTP and NTP timeserver configuration.
- Host: GitHub
- URL: https://github.com/geerlingguy/time-pi
- Owner: geerlingguy
- License: gpl-3.0
- Created: 2024-12-13T15:22:25.000Z (over 1 year ago)
- Default Branch: master
- Last Pushed: 2026-02-25T22:16:33.000Z (4 months ago)
- Last Synced: 2026-02-26T00:38:04.316Z (4 months ago)
- Topics: gps, ntp, ptp, raspberry-pi, time, time-server
- Language: Python
- Homepage:
- Size: 1.97 MB
- Stars: 219
- Watchers: 9
- Forks: 9
- Open Issues: 8
-
Metadata Files:
- Readme: README.md
- Funding: .github/FUNDING.yml
- License: LICENSE
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README
# Time Pi
[](https://github.com/geerlingguy/time-pi/actions/workflows/ci.yml)
A Raspberry Pi stratum 1 time server.
Takes in GPS (or potentially other stratum 0 time sources), spits out NTP, PTP, etc.
## Setup
### Hardware
To run a decent time server (with high accuracy), you need a few things:
- A computer running Linux (all the nice tooling for network time is availabe here)
- A high quality time source (GPS is most commonly used these days)
- A network adapter capable of hardware timestamping (Intel and ASIX make some good NICs for time-related applications)
There are many options for each of the above items—for example, many use [Adafruit's Ultimate GPS HAT](https://www.adafruit.com/product/2324) or its [USB equivalent](https://www.adafruit.com/product/4279) for GPS acquisition, and for PTP, you can use a Compute Module 4 or 5's built-in NIC (with [PPS in or out](https://www.jeffgeerling.com/blog/2022/ptp-and-ieee-1588-hardware-timestamping-on-raspberry-pi-cm4)), or add on a compatible NIC on the Pi 5 with something like the [uPCIty Lite](https://amzn.to/4iUn9ke).
My own hardware configuration—which is the basis for the code in this repository, consists of:
- Computer: Raspberry Pi 5 model B
- Time source: u-blox ZED-F9T-00B-01 (installed on [TimeHAT V4](https://github.com/geerlingguy/raspberry-pi-pcie-devices/issues/674))
- NIC: Intel i226-LM (installed on [TimeHAT V4](https://github.com/geerlingguy/raspberry-pi-pcie-devices/issues/674))
A precise GPS signal for nanosecond-accurate time requires a decent antenna with as clear a view of the sky as possible. Some GPS receivers are better than others, but even USB receivers will do better than NTP!
I use a small [active GPS antenna](https://amzn.to/4gdhBj1) for testing, but for permanent installation it is best to mount a [higher-quality GPS antenna](https://www.meinbergglobal.com/english/products/gps-glonass-l1-antenna.htm) outside, clear of obstructions.
### Software
Make sure you have Ansible installed. Copy the following example files and customize them according to your setup:
- `example.hosts.ini` to `hosts.ini`
- `example.config.yml` to `config.yml`
Now run the Ansible playbook:
```
ansible-playbook main.yml
```
This playbook will configure:
- [GPSd](https://gpsd.gitlab.io/gpsd/gpsd.html): interface with the u-blox GPS and provide GPS data to other applications
- [Chrony](https://chrony-project.org): NTP server, which also sync GPS time (with Internet NTP server backup) to the system clock
- [Linux PTP](https://linuxptp.nwtime.org): synchronize the system clock to the NIC PHC (Physical Hardware Clock), and set up the Pi as a PTP grandmaster clock
> **Intel i226 Notes**: Currently I can't get the i226 to work with DHCP at all, so I have to manually set an IP address using `nmtui`. It also [doesn't work at 2.5 Gbps currently](https://github.com/geerlingguy/raspberry-pi-pcie-devices/issues/674#issuecomment-2533117275), and it can't be overridden via Linux, so I make sure to plug it into a 1 Gbps port on my network.
## GPS Notes
Using u-blox GPS modules, you may encounter a baud rate mismatch. Many of the u-blox modules default to `38400` baud, but this project recommends `115200` baud for slightly faster timing updates.
```
# Get the protocol version ('PROTVER')
ubxtool -p MON-VER
...
UBX-MON-VER:
swVersion EXT CORE 4.04 (7f89f7)
hwVersion 00190000
extension ROM BASE 0x118B2060
extension FWVER=SPG 4.04
extension PROTVER=32.01
...
# Set the version in ubxtool options
export UBXOPTS="-P 32.01"
# Set the baud rate to 115200
ubxtool -S 115200
# Persist the setting
ubxtool -p SAVE
```
**KNOWN ISSUE**: The baud setting is currently not persisting across reboots. See [this GitHub issue](https://github.com/geerlingguy/time-pi/issues/11) for updates.
`ubxtool` is installed as part of the `gpsd-clients` package, which is automatically installed by this playbook.
For more on how to set the baud rate (or tweak other GPS module parameters), see [millerjs.org's ubxtool page](https://wiki.millerjs.org/ubxtool) and the [ubxtool examples](https://gpsd.io/ubxtool-examples.html) page.
## Usage and Debugging
Some handy commands:
```
# GPS-related debugging
sudo systemctl status gpsd # check gpsd status
gpsmon -n # monitors gpsd output
cgps -s # also monitors gps output
# PTP timestamping debugging
ethtool -T eth0 # or eth1, lists hardware clock info
# Chrony debugging
chronyc sources -v # shows sources with documentation of fields
chronyc tracking # shows detailed timing data
# Check on NTP service from another computer
ntpdate -q [ip of grandmaster]
# Check on PTP clocks and offsets (assuming ptp4l is running)
wget https://tsn.readthedocs.io/_downloads/f329e8dec804247b1dbb5835bd949e6f/check_clocks.c
gcc -o check_clocks check_clocks.c
sudo ./check_clocks -d eth0 # or eth1 (the interface you're using for PTP)
# Check offset between NIC PHY and system clock
sudo phc_ctl eth1 cmp # should be nearly -37000000000ns
```
Much of the work that went into this project was documented in [this thread on the TimeHat v2](https://github.com/geerlingguy/raspberry-pi-pcie-devices/issues/674).
## GPS / GNSS Module debugging
Like cellular modems, GPS modules can be a bit tricky, using arcane syntaxes and custom protocols for communication.
For the NEO-M9N module, the default `baud` rate is a little low for my liking, but to get it working, I had to go through a lengthy process learning `ubxtool`.
To configure my module for `115200` baud, I did the following:
```
# Set the baud rate
ubxtool -S 115200
# Save the settings (get the `-P` PROTVER with `ubxtool -p MON-VER`)
$ ubxtool -p SAVE -P 32.01
# Update the rate in your GPSd config and restart `gpsd`
sudo nano /etc/default/gpsd
sudo systemctl restart gpsd
# Test the settings by rebooting the GPS module manually.
$ ubxtool -p COLDBOOT -P 32.01
```
See this issue for more: [Debug NEO-M9N module on TimeHAT V2](https://github.com/geerlingguy/time-pi/issues/11).
## Slave / Client Setup
For PTP, you need to install and configure PTP for Linux on slave/client machines, and synchronize them to the master/server node as well.
An example configuration for a slave/client node is set up in `ptp-client-node.yml`, and further examples may be provided in the future.
## Other Hobbyist Time Servers
- [LeapSecond.com](http://www.leapsecond.com)
- [Austin's Nerdy Things: Nanosecond accurate PTP Pi server](https://austinsnerdythings.com/2025/02/18/nanosecond-accurate-ptp-server-grandmaster-and-client-tutorial-for-raspberry-pi/)
- [Andreas Spiess: NTP Server from GPS Satellites](https://www.youtube.com/watch?v=RKRN4p0gobk)
- [Jeff Geerling: Time Card mini for GPS and OXCO on Pi](Time Card mini adds Pi, GPS, and OCXO to your PC)
## Other Time Resources I found Interesting
- [Where does my computer get the time from?](https://dotat.at/@/2023-05-26-whence-time.html) (good overview of the sources of modern NTP + GPS time, with the history of each source)
## License
GPLv3 or Later
## Author
[Jeff Geerling](https://www.jeffgeerling.com), with assistance from Ahmad Byagowi and Oleg Obleukhov from Meta.