The display shows current NTP time and date, the PPS signal locking state, Stratum level, the offset to the NTP time, the number of satellites that are currently used, and, if no PPS lock is available, alternatively the address of the time server used.
If you see an address of some time server, PPS lock is not (yet) working.
Note: the main script chronotron.py defines a start_time and an end_time, used to switch on the LCD backlight (at start_time) and switch it off at (end_time). If you want permanent backlight, simply set start_time and end_time to None.
- Display: HD44780 2004 LCD Display 4x20 characters with I2C interface (address 0x27 is assumed by the code), use for example:
- Adafruit LCD 4x20 and I2C Adapter, description: (https://learn.adafruit.com/i2c-spi-lcd-backpack). Advantage: Stemma QT adapter (QWIIC) that can be also added to Raspberry PI for clean cabling.
- Amazon kit sunfounder kit
- AliExpress kit [TZT Five Star](https://de.aliexpress.com/item/1005001679675215.html
Make sure that I2C is enable on your Raspberry PI.
Connect the LCD Display the GND, 5V and SDA and SCL pins or the Raspberry PI.
Note: Raspberry PI uses 3.3V logic, and the LCD Display is connected to 5V. This should not be a problem, since the lcd just receives from Raspberry PI. If you want to be on the safe side, either try to power the LCD with 3.3V, or use a logic-level-converter.
Note: if your display uses a different address than
0x27, or if you are using a very old Raspberry that still usessm_bus=0, you need to adapt:
lcd = LcdDisplay(sm_bus=1, i2c_addr=0x27, cols=20, rows=4)Old Raspis use sm_bus=0.
Note: if the LCD screen looks inverted or too faint, or no output is visible at all, use the potentiometer on the adapter-board to adjust the contrast.
Note: Standard Raspberry Pi OS (tested with 'Bookworm') is recommended and used below
This project uses Martijn Braam's python gpsd driver https://github.com/MartijnBraam/gpsd-py3 (minimum version 0.3.0, and smbus (already available on some distributions).
With recent python and Raspberry Pi OS updates, installation became a bit more complicated, since it is no longer easily allowed to install PIP modules into the root context. There are two solutions
Note: there is a proper way to do things, see next chapter using
venv
If you want to avoid working with Python virtual environments (e.g because the Raspberry is simply a single-use time server), you can simply force installation of gpsd-py3 into root context, which is generally considered bad practice, but in our case of limited risk, since gpsd-py3 has no further dependencies and is not part of any package manager.
Install with:
# should be already installed:
sudo apt install python3-smbus
# You need at least version 0.3.0 of gpsd-py3, otherwise number of satellites is not supported
sudo pip install --break-system-packages gpsd-py3Prep variant 2 - Use proper Python virtual environments for installations, avoiding --break-system-packages
The proper way to install is to create a virtual environment for chronotron:
If chronotron does not start, check with sudo systemctl status chronotron: It will show if it can't
import a required packages.
cd /opt
# create a virtual env at /opt/chronotron
sudo python -m venv chronotron
# make the directory tree /opt/chronotron accessible for your current user
chown -R $USER:$USER chronotron
cd chronotron
# activate the virtual environment, which allows to install pip modules into it.
source bin/activate
# No root!
pip install smbus gpsd-py3Now, while the venv is active, you have access to the packages installed within it. You can deactivate a venv with deactivate and re-activate it again with source bin/activate while being in the /opt/chronotron directory.
When using systemd use the chronotron_venv.service, (rename to chronotron.service). This uses the python version of the chronotron venv we just created.
- Clone the repository
git clone https://github.com/domschl/RaspberryNtpServer
cd RaspberryNtpServer/src- Copy the python files to
/opt/chronotron:
# Skip directory creation, if you have already created a chronotron venv
mkdir /opt/chronotron
chown -R $USER:$USER /opt/chronotron
# Now copy:
cp button.py chronotron.py i2c_lcd.py /opt/chronotron- Install the systemd service
- If you did not use a python virtual environment, use
chronotron.service:
# no venv
sudo cp chronotron.service /etc/systemd/system- If you used a virtual environment, use
chronotron_venv.serviceand rename it:
# with chronotron venv
sudo cp chronotron_venv.service /etc/systemd/system/chronotron.serviceWhile the venv is active, check with which python that the path to the venv's python matches the configuration of your systemd file, the line ExecStart=/opt/chronotron/bin/python /opt/chronotron/chronotron.py should use the python from within the venv, which automatically activates the venv when the service is started.
- Both variants
Enable the systemd server chronotron with:
sudo systemctl enable chronotron
sudo systemctl start chronotronCheck, if everthing works:
sudo systemctl status chronotronIf everything worked, the output should be something like:
chronotron.service - Display chrony statistics on 4x20 LCD
Loaded: loaded (/etc/systemd/system/chronotron.service; enabled; preset: disabled)
Active: active (running) since Tue 2022-10-25 14:44:17 CEST; 2 months 15 days ago
Main PID: 370 (chronotron.py)
Tasks: 2 (limit: 3921)
CPU: 3d 5h 34min 24.354s
CGroup: /system.slice/chronotron.service
└─370 /usr/bin/python /opt/chronotron/chronotron.py
Dec 21 09:38:37 chronotron systemd[1]: Started chronotron.service - Display chrony statistics on 4x20 LCD.
Dec 21 09:38:37 chronotron chronotron.py[2628]: INFO:Chronotron:Chronotron version 2.0.0 starting
Dec 21 09:38:37 chronotron chronotron.py[2628]: INFO:Chronotron:Chrony aquired lock to time source
Dec 21 09:38:37 chronotron chronotron.py[2628]: INFO:Chronotron:Chrony receiving time source from PPS
Dec 21 09:38:37 chronotron chronotron.py[2628]: INFO:Chronotron:Chrony stratum level changed to 1
Dec 21 09:38:37 chronotron chronotron.py[2628]: INFO:Chronotron:Chrony locked to high precision GPS PPS signal
Note: if you are using a chronotron virtual python environment (venv) it should look like this:
CGroup: /system.slice/chronotron.service
└─8197 /opt/chronotron/bin/python /opt/chronotron/chronotron.py
Notice the path for python: in case of venv, we use the venv's python version.
- Time and date according to NTP
- New: The current stratum level is displayed as
S[1]for stratum level 1. - Shows the output of
chronyc tracking, entrysystem time, the time difference to the NTP reference (see below for further information). L[ ]no lock,L[*]lock. A lock (*) indicates that time synchronisation is established, either via remote NTP servers or GPS + PPSPPSsignales that the lock is active using GPS and PPS, the server is in high-precision stratum 1 mode. If instead a hostname is displayed, then PPS is NOT active, and the network is used for time synchronisation, resulting in lower precision.SAT[nn],nnis the number of satellites that are actively used for time synchronisation.- Shows output of
chronyc sources, the last column, "adjusted offset", of the currently active source, which is the estimated error (see below for further information)
Marked with >>>nnnn.nnnn<<< is the information displayed at (2). Here, the system is 0.000000100 seconds faster than NTP ref.
chronyc tracking
# sample output:
Reference ID : 50505300 (PPS)
Stratum : 1
Ref time (UTC) : Tue Jul 11 07:22:07 2023
System time : >>>0.000000100<<< seconds fast of NTP time
Last offset : +0.000000030 seconds
RMS offset : 0.000010080 seconds
Frequency : 10.392 ppm fast
Residual freq : -0.006 ppm
Skew : 0.005 ppm
Root delay : 0.000000001 seconds
Root dispersion : 0.000384213 seconds
Update interval : 16.0 seconds
Leap status : Normal
Marked with >>>nnn<<< is the information displayed at (6).
Here the estimated error of the PPS signal is 591ns
chronyc sources -v
# sample output with explanation (-v paramenter):
.-- Source mode '^' = server, '=' = peer, '#' = local clock.
/ .- Source state '*' = current best, '+' = combined, '-' = not combined,
| / 'x' = may be in error, '~' = too variable, '?' = unusable.
|| .- xxxx [ yyyy ] +/- zzzz
|| Reachability register (octal) -. | xxxx = adjusted offset,
|| Log2(Polling interval) --. | | yyyy = measured offset,
|| \ | | zzzz = estimated error.
|| | | \
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
#? GPS 0 4 0 780 +43ms[ +43ms] +/- 200ms
#* PPS 0 4 0 782 +186ns[ +217ns] +/- >>>591ns<<<
^? 2003:2:2:140:194:25:134:> 2 10 377 340 +141us[ +141us] +/- 17ms
^? time.ontobi.com 2 10 377 264 +139us[ +139us] +/- 13ms
^? bblock.dev 2 10 377 631 +209us[ +209us] +/- 12ms
^? time01.nevondo.com 2 10 377 721 +181us[ +181us] +/- 28ms
^? static.33.250.47.78.clie> 3 10 377 1168 -191us[ -213us] +/- 15ms```
- https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/configuring_basic_system_settings/using-chrony_configuring-basic-system-settings
- chronyc documentation
The chronotron.py systemd service checks periodically chronyc for NTP statistics (chronyc must be in the path!), and uses gpsd for the GPS statistics (number of satellites).
button.pyis currently not used.i2c_lcd.pyis a buffered driver for the LCD display.chronotron.serviceis the systemd service file.