author	date	url	license
Daniel Mohr	2023-08-02	https://github.com/ug-cp/precise_sntp	BSD 3-Clause License

precise_sntp -- precise Simple Network Time Protocol

This library is an implementation of the Simple Network Time Protocol (SNTPv4) for the arduino platform.

In contrast to other implementations this library allows sub-second precision. Further you can set the (S)NTP server to use by IP or by DNS name.

As all (S)NTP implementations for arduino it is simplified.

Since in SNTP no mitigation algorithms (clock filter, clock adjust, ...) are used, a precision of sub-milliseconds is not meaningful. Therefore we concentrate here on getting the time with a precision of a few milliseconds.

The returned epoch in different formats is always calculated using millis(). millis() will overflow after about 50 days and the returned epoch is not correct anymore. To handle this you have to call update, update_adapt_poll_period or check_millis_overflow at least every 24 days. This should work for about 8926 years, then the check counter will overflow.

Since no clock adjust is done, the time is not always continuous. Every time the time is updated from a time server the time could jump.

• home: github.com/ug-cp/precise_sntp
• mirror: gitlab.com/ug-cp/precise_sntp
• Arduino Library Manager: www.arduino.cc/reference/en/libraries/precise_sntp

Install

To use/install this library, you can open the Library Manager in the Arduino IDE and install it from there. This is the recommended way.

Or if you use Arduino CLI the recommended way is arduino-cli lib install precise_sntp

Or to install this library use Add .ZIP Library ... in your Arduino IDE to add the zip archive ....zip you can download from this repository. Or you can use archives from latest release.

Or just copy the content of this repository to your Arduino libraries, e. g.:

git clone https://github.com/ug-cp/precise_sntp.git ~/Arduino/libraries/precise_sntp

Usage

This library does not create/handle network. For example, you can do this on your own by using the libraries Ethernet.h and EthernetUdp.h.

After including this library you have to create an instance sntp of the class and to provide a EthernetUDP instance to handle udp sending and receiving.

#include <EthernetUdp.h>
#include <precise_sntp.h>
EthernetUDP udp;
precise_sntp sntp(udp);

Further you should call sntp.update() regularly to get or update the time from a time server.

void loop() {
  sntp.update();
}

Maybe cou can use force_update_iburst() in the setup routine to speed up the initial synchronization.

void setup() {
  sntp.force_update_iburst();
}

Tested

It was tested on SAMD21 (Arduino MKR1000 using Ethernet and Arduino MKR WiFi 1010 using WI-FI) -- see examples.

Examples

In the folder examples you can find some examples.

License, Copyright: BSD 3-Clause License

Copyright (c) 2022, 2023 Daniel Mohr and University of Greifswald, Institute of Physics, Colloidal (dusty) plasma group

All rights reserved.

see: LICENSE