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GNAT'S Nearly Accurate Time Server

A tiny and very basic NTP server based on a GPS receiver.
Runs on the SeeedStudio XIAO ESP32C3 or XIAO ESP32S3

icon

Changes

2023-08-03: Added the ethernet-test branch in which an ENC28J60 based Ethernet module is used to connect to the local area network instead of Wi-Fi.

2023-07-19: Added optional support for a DS3231 battery powered real time clock. The RTC is not a backup time source; it is only used to set the initial time until the correct time is acquired by the GPS receiver.

Hardware used

  • ESP32 development board such as XIAO ESP32C3 or XIAO ESP32S3
  • GPS receiver supported by TinyGPSPlus such as the ATGM336H 5N-31
  • DS3231 battery backed real time clock (optional)
  • SSD1306 128x64 I2C OLED display (optional)
  • Shematic

Libraries

  • TinyGPSPlus by Mikal Hart at Arduiniana. The library reads the $GNRMC NMEA messages from the GPS receiver and makes available the date and time data, among many other bits of information. Licence: unknown.

  • ntp_server is a modified version of the NTP server (ntp_server.h and ntp_server.cpp) in the ElektorLabs 180662 mini NTP with ESP32. There is a project description in the ElektorMag mini-NTP server with GPS. Licence: GPLv3 or later at user choice.

  • OLED SSD1306 (ESP8266/ESP32/Mbed-OS) by ThingPulse is used to print the date and time on a small OLED screen. Licence: MIT.

  • Rtc by Michael Miller (Makuna) is used to read a battery-powered DS3231 real time clock which will provide the initial time to set the ESP real time clock until GPS time is available. Licence: LGPLv3

  • smalldebug just defines two macros: DBG(...) and DBG(...). These are used throughout the code instead of Serial.println(...) and Serial.printf(...). The advantage of using these macros is that all the print statements will be stripped from the compiled firmware when the ENABLE_DBG macro is set to 0. Licence: None.

Further documentation

GNATS, a Tiny Basic ESP32 GPS Based NTP Server

Using a Local Network Time Server

Warning

GNATS should not be used as the primary time source. However, it is accurate enough as a backup time source when access to better clocks is lost.

Note

Edit secrets.h.template and save it as secrets.h in the src directory before compiling the firmware.

Licence

The BSD Zero Clause (SPDX: 0BSD) licence applies to all source not covered by another licence.