#NtpClientLib

##Introduction There are some NTP client examples around. You can see some examples, like [this].

In a device like ESP8266 or any Internet connected Arduino having NTP synchronization is well convenient. Using that example you can add NTP client to your projects but I was looking for a quicker way to add it, using something like NTPClient class.

So I decided to do my own NTP client libary to sync ESP8266 time via WiFi using Arduino IDE. It can also be used on any ethernet connected Arduino. WiFi is not supported on Arduino yet. ##Description This is a NTP library to be able to get time from NTP server with my ESP8266s. Initial support for regular Arduino is available. Please test it and inform via GitHub.

Using the library is fairly easy. A NTP object is created inside library. You may use default values by using NTP.begin() without parameters. After that synchronization is done regularly without user intervention. Some parameters can be adjusted: server, sync frequency, time offset.

You don't need anything more. Time update is managed inside library so, after NTP.begin() no more calls to library are needed.

Update frequency is higher (every 15 seconds as default) until 1st successful sync is achieved. Since then, your own (or default 1800 seconds) adjusted period applies. There is a way to adjust both period if needed.

In order to reduce scketch size, ESP8266 version makes use of internal Espressif SDK routines that already implement SNTP protocol.

This library includes an uptime log too. It counts number of seconds since scketch is started. It can be checked calling NTP.getUptime() or NTP.getUptimeString() for a human readable string.

##Example for Arduino

#include <TimeLib.h>
#include <NtpClientLib.h>
#include <SPI.h>
#include <EthernetUdp.h>
#include <Ethernet.h>
#include <Dns.h>
#include <Dhcp.h>

// Enter a MAC address for your controller below.
// Newer Ethernet shields have a MAC address printed on a sticker on the shield
byte mac[] = {
	0x00, 0xAA, 0xBB, 0xCC, 0xDE, 0x02
};

EthernetClient client;

void setup()
{
	Serial.begin(115200);
	if (Ethernet.begin(mac) == 0) {
		Serial.println("Failed to configure Ethernet using DHCP");
		// no point in carrying on, so do nothing forevermore:
		for (;;)
			;
	}
	NTP.onNTPSyncEvent([](NTPSyncEvent_t error) {
		if (error) {
			Serial.print("Time Sync error: ");
			if (error == noResponse)
				Serial.println("NTP server not reachable");
			else if (error == invalidAddress)
				Serial.println("Invalid NTP server address");
		}
		else {
			Serial.print("Got NTP time: ");
			Serial.println(NTP.getTimeDateString(NTP.getLastNTPSync()));
		}
	});
	NTP.begin("es.pool.ntp.org", 1, true);
	NTP.setInterval(63);
}

void loop()
{
	static int i = 0;
	static int last = 0;

	if ((millis() - last) > 5100) {
		//Serial.println(millis() - last);
		last = millis();
		Serial.print(i); Serial.print(" ");
		Serial.print(NTP.getTimeDateString()); Serial.print(". ");
		Serial.print("Uptime: ");
		Serial.print(NTP.getUptimeString()); Serial.print(" since ");
		Serial.println(NTP.getTimeDateString(NTP.getFirstSync()).c_str());

		i++;
	}
	delay(0);
	Ethernet.maintain(); // Check DHCP for renewal
}

##Example for ESP8266

#include <TimeLib.h>
#include <NtpClientLib.h>
#include <ESP8266WiFi.h>

#define YOUR_WIFI_SSID "YOUR_WIFI_SSID"
#define YOUR_WIFI_PASSWD "YOUR_WIFI_PASSWD"

void setup()
{
	Serial.begin(115200);
	WiFi.mode(WIFI_STA);
	WiFi.begin(YOUR_WIFI_SSID, YOUR_WIFI_PASSWD);
	NTP.onNTPSyncEvent([](NTPSyncEvent_t error) {
		if (error) {
			Serial.print("Time Sync error: ");
			if (error == noResponse)
				Serial.println("NTP server not reachable");
			else if (error == invalidAddress)
				Serial.println("Invalid NTP server address");
		}
		else {
			Serial.print("Got NTP time: ");
			Serial.println(NTP.getTimeDateString(NTP.getLastNTPSync()));
		}
	});
	NTP.begin("pool.ntp.org", 1, true);
	NTP.setInterval(1800);
}

void loop()
{
	static int i = 0;
	static int last = 0;

	if ((millis() - last) > 5100) {
		last = millis();
		Serial.print(i); Serial.print(" ");
		Serial.print(NTP.getTimeDateString()); Serial.print(". ");
		Serial.print("WiFi is ");
		Serial.print(WiFi.isConnected() ? "connected" : "not connected"); Serial.print(". ");
		Serial.print("Uptime: ");
		Serial.print(NTP.getUptimeString()); Serial.print(" since ");
		Serial.println(NTP.getTimeDateString(NTP.getFirstSync()).c_str());

		i++;
	}
	delay(0);
}

##Performance Don't expect atomic-clock-like precission. This library does not take network delay into account neither uses all NTP mechanisms available to improve accuracy. It is in the range of 1 to 2 seconds. Enough for most projects.

##Dependencies This library makes use of [Time] library. You need to add it to use NTPClientLib [Time]: https://github.com/PaulStoffregen/Time.git

---

ntpClient.ino is an example of how this library works. It shows current time and uptime every 5 seconds as soon it gets synchronized. [this]: https://github.com/esp8266/Arduino/tree/master/libraries/ESP8266WiFi/examples/NTPClient