DIY ESP32 based Stratum 1 NTP server that gets his time from a GPS module and provides NTP to clients via Wifi. The ESP32 can connect to your Wifi access point, when you set your connection credentials in secrets.h or act as an independent Wifi access point, if connection to your Wifi failed. It is a very minimalistic NTP server (Version 3) without fancy stuff like authentication, control messages, cryptographic keys...
Inspired by ESP32TimeServer by Rob Latour
My code is licensed under the terms of the CC0 Copyright (c) 2024 codingABI.
Used external libraries from Arduino IDE Library Manager:
- TinyGPS (by Mikal Hart, Version 13.0.0, GPL-3.0 license)
- Microcontroller ESP32 LOLIN32 (other ESP32s should also works)
- GY-NEO6MV2 NEO-6M GPS-Module
Arduino IDE 1.8.19 (Without "real portable" support version 2.* makes no sense for me https://forum.arduino.cc/t/arduino-ide-2-0-portable/)
Board manager: esp32, by Expressif Systems, Version 3.0.5
- https://www.rfc-editor.org/rfc/rfc5905
- https://www.rfc-editor.org/rfc/rfc1305
- https://tickelton.gitlab.io/articles/ntp-timestamps/
- https://learn.microsoft.com/en-US/windows-server/networking/windows-time-service/how-the-windows-time-service-works
Windows 11 NTP client (IP 192.168.178.22) sends a NTP request to the ntpGPSServer (IP 192.168.178.27)
The ntpGPSServer (IP 192.168.178.27) sends the NTP response back to the Windows 11 NTP client (IP 192.168.178.22)
Interestingly, a Windows 11 w32tm /stripchart /computer:... command sends significantly different attributes than a common Windows 11 NTP client request:
- UDP-Source port is a highport and not 123
- NTP Version is 1
- reference timestamp (retime) is 0
- Reference ID (refid) is 0
- Root Dispersion (rootdisp) is 0
- Poll is 1s
- Precision is 1s
- Stratum is 0
