Increase time accuracy

NTPClient.cpp

@@ -82,54 +82,124 @@ void NTPClient::begin(int port) {
 }
 
 bool NTPClient::forceUpdate() {
-  #ifdef DEBUG_NTPClient
-    Serial.println("Update from NTP Server");
-  #endif
-
   // flush any existing packets
   while(this->_udp->parsePacket() != 0)
     this->_udp->flush();
 
+  uint32_t tik,tok; //tik,tok to record wait time, replace timeout
   this->sendNTPPacket();
+  tik=millis();
+  #ifdef DEBUG_NTPClient
+    Serial.println("sent ntp packet");
+  #endif
 
   // Wait till data is there or timeout...
-  byte timeout = 0;
-  int cb = 0;
+  uint16_t cb = 0;
   do {
-    delay ( 10 );
+    delay (1); //poll more frequently to get high accuarcy
     cb = this->_udp->parsePacket();
-    if (timeout > 100) return false; // timeout after 1000 ms
-    timeout++;
+    if ((millis()-tik)>this->_ntp_timeout){
+      this->_last_fail=millis();
+      return false;
+    }
   } while (cb == 0);
-
-  this->_lastUpdate = millis() - (10 * (timeout + 1)); // Account for delay in reading the time
+  tok=millis();
+  #ifdef DEBUG_NTPClient
+    Serial.println("got ntp packet.");
+    Serial.print("tik, tok, (tok-tik)/2: ");
+    Serial.print(tik);Serial.print(", ");
+    Serial.print(tok);Serial.print(", ");
+    Serial.println((tok-tik)/2.0);
+  #endif
 
   this->_udp->read(this->_packetBuffer, NTP_PACKET_SIZE);
-
-  unsigned long highWord = word(this->_packetBuffer[40], this->_packetBuffer[41]);
-  unsigned long lowWord = word(this->_packetBuffer[42], this->_packetBuffer[43]);
+  uint32_t high_word,low_word;
+  uint32_t receive_int,transmit_int; //integer part
   // combine the four bytes (two words) into a long integer
   // this is NTP time (seconds since Jan 1 1900):
-  unsigned long secsSince1900 = highWord << 16 | lowWord;
+  high_word=word(this->_packetBuffer[32],this->_packetBuffer[33]);
+  low_word=word(this->_packetBuffer[34],this->_packetBuffer[35]);
+  receive_int=(high_word<<16) | low_word;
+  high_word=word(this->_packetBuffer[40],this->_packetBuffer[41]);
+  low_word=word(this->_packetBuffer[42],this->_packetBuffer[43]);
+  transmit_int=(high_word<<16) | low_word;
+  #ifdef DEBUG_NTPClient
+    Serial.print("receive_int, transmit_int: ");
+    Serial.print(receive_int);Serial.print(", ");
+    Serial.println(transmit_int);
+  #endif
+
+  float receive_dec=0,transmit_dec=0; //decimal part
+  high_word=word(this->_packetBuffer[36],this->_packetBuffer[37]);
+  receive_dec=high_word/65536.0;
+  #ifdef DEBUG_NTPClient
+    Serial.print("receive_dec, transmit_dec: ");
+    Serial.print(high_word,HEX);Serial.print(", ");
+    Serial.print(receive_dec,6);Serial.print(", ");
+  #endif
+  high_word=word(this->_packetBuffer[44],this->_packetBuffer[45]);
+  transmit_dec=high_word/65536.0;
+  #ifdef DEBUG_NTPClient
+    Serial.print(high_word,HEX);Serial.print(", ");
+    Serial.println(transmit_dec,6);
+  #endif
+
+  float ping_delay;
+  ping_delay=(tok-tik)/1000.0-(transmit_int-receive_int)-(transmit_dec-receive_dec);
+  ping_delay/=2.0;
+  if(ping_delay<=0){
+    Serial.println("ERROR: ping_delay < 0.0!");
+  }
+
+  this->_lastUpdate=tok;
+  this->_currentEpoc=transmit_int - SEVENZYYEARS ;
+  this->_current_epoc_dec=ping_delay+transmit_dec;
+  if(this->_current_epoc_dec>1){
+    this->_currentEpoc+=(int)this->_current_epoc_dec;
+    this->_current_epoc_dec-=(int)this->_current_epoc_dec;
+  }
 
-  this->_currentEpoc = secsSince1900 - SEVENZYYEARS;
+  #ifdef DEBUG_NTPClient
+    Serial.print("current Epoc: ");
+    Serial.print(this->_currentEpoc);Serial.print(" ");
+    Serial.println(this->_current_epoc_dec,6);
+  #endif
 
   return true;  // return true after successful update
 }
 
-bool NTPClient::update() {
-  if ((millis() - this->_lastUpdate >= this->_updateInterval)     // Update after _updateInterval
-    || this->_lastUpdate == 0) {                                // Update if there was no update yet.
-    if (!this->_udpSetup) this->begin();                         // setup the UDP client if needed
-    return this->forceUpdate();
+int8_t NTPClient::update() {
+  uint32_t now=millis();
+  if(now>=this->_lastUpdate){ //if not overflow
+      if(now-this->_lastUpdate>=this->_updateInterval){
+          if(now-this->_last_fail >= 1500){
+              return this->forceUpdate();
+          }else{
+              return 3; //return 3 if last failed was just happen
+          }
+      }
+  }else{ //if overflowed
+      if(now+0xffffffff-this->_lastUpdate >= this->_updateInterval){ 
+          if(now+0xffffffff-this->_last_fail >= 1500){
+              return this->forceUpdate();
+          }else{
+              return 3;
+          }
+      }
   }
-  return false;   // return false if update does not occur
+  return 2;   // return 2 if update does not occur
 }
 
 unsigned long NTPClient::getEpochTime() const {
   return this->_timeOffset + // User offset
          this->_currentEpoc + // Epoc returned by the NTP server
-         ((millis() - this->_lastUpdate) / 1000); // Time since last update
+         ((millis() - this->_lastUpdate + this->_current_epoc_dec*1000)/1000.0); // Time since last update
+}
+
+float NTPClient::get_millis() const{
+  float ms = millis() - this->_lastUpdate + this->_current_epoc_dec*1000.0;
+  ms-=(int)(ms/1000)*1000;
+  return ms;
 }
 
 int NTPClient::getDay() const {
@@ -174,7 +244,16 @@ void NTPClient::setUpdateInterval(unsigned long updateInterval) {
 }
 
 void NTPClient::setPoolServerName(const char* poolServerName) {
-    this->_poolServerName = poolServerName;
+  this->_poolServerName = poolServerName;
+}
+
+void NTPClient::setPoolServerIP(IPAddress server_ip){
+  this->_poolServerIP   = server_ip;
+  this->_poolServerName = NULL;
+}
+
+void NTPClient::setTimeout(uint16_t t_ms){
+   this->_ntp_timeout=t_ms;
 }
 
 void NTPClient::sendNTPPacket() {

NTPClient.h

@@ -7,6 +7,7 @@
 #define SEVENZYYEARS 2208988800UL
 #define NTP_PACKET_SIZE 48
 #define NTP_DEFAULT_LOCAL_PORT 1337
+#define DEBUG_NTPClient
 
 class NTPClient {
   private:
@@ -21,7 +22,11 @@ class NTPClient {
     unsigned long _updateInterval = 60000;  // In ms
 
     unsigned long _currentEpoc    = 0;      // In s
-    unsigned long _lastUpdate     = 0;      // In ms
+    float         _current_epoc_dec = 0;    // In s, decimal part of current epoc
+    uint32_t      _lastUpdate     = 0xff000000;// In ms
+
+    uint16_t      _ntp_timeout    = 1000;    // In ms
+    uint32_t      _last_fail      = 0xffff0000; // In ms
 
     byte          _packetBuffer[NTP_PACKET_SIZE];
 
@@ -44,6 +49,20 @@ class NTPClient {
      */
     void setPoolServerName(const char* poolServerName);
 
+    /**
+     * clear time server and set ip
+     *
+     * @param ServerIP
+     */
+    void setPoolServerIP(IPAddress server_ip);
+
+    /**
+     * Set ntp timeout, recommand not above 1000ms
+     *
+     * @param t_ms
+     */
+    void setTimeout(uint16_t t_ms);
+
     /**
      * Starts the underlying UDP client with the default local port
      */
@@ -58,9 +77,12 @@ class NTPClient {
      * This should be called in the main loop of your application. By default an update from the NTP Server is only
      * made every 60 seconds. This can be configured in the NTPClient constructor.
      *
-     * @return true on success, false on failure
+     * @return 1(true) on updated and success
+     *         0(false) on updated and failure
+     *         2 on not time to update
+     *         3 on it's time to update but last failed was just happen, so it decided to wait more
      */
-    bool update();
+    int8_t update();
 
     /**
      * This will force the update from the NTP Server.
@@ -95,6 +117,11 @@ class NTPClient {
      */
     unsigned long getEpochTime() const;
 
+    /**
+     * @return ms of this second, in ms
+     */
+    float get_millis() const;
+
     /**
      * Stops the underlying UDP client
      */

examples/ntp_demo.ino

@@ -0,0 +1,94 @@
+// change next line to use with another board/shield
+#include <WiFi.h>
+//#include <ESP8266WiFi.h>
+//#include <WiFi.h>
+//#include <WiFi101.h>
+#include <WiFiUdp.h>
+#include "NTPClient.h"
+
+WiFiUDP ntpUDP;
+NTPClient my_time_client(ntpUDP);
+
+void connect_wifi(char * ssid,char * password){
+    Serial.print("wifi connecting...");
+    WiFi.begin(ssid,password);
+    while(WiFi.status()!= WL_CONNECTED){
+        delay(1000);
+        Serial.print(".");
+    }
+
+    Serial.println("\nwifi connected!");
+    Serial.print("ip: ");
+    Serial.println(WiFi.localIP());
+    Serial.print("netmask: ");
+    Serial.println(WiFi.subnetMask());
+    Serial.print("gateway: ");
+    Serial.println(WiFi.gatewayIP());
+    Serial.print("channel: ");
+    Serial.println(WiFi.channel());
+    Serial.print("auto-reconnect: ");
+    Serial.println(WiFi.getAutoReconnect());
+}
+
+inline void sync_time(){
+    my_time_client.begin();
+    my_time_client.setTimeOffset(28800);
+    my_time_client.setUpdateInterval(20000);
+    //my_time_client.setPoolServerName("0.ubuntu.pool.ntp.org");
+    my_time_client.setPoolServerName("192.168.1.200");
+    //smaller timeout will give you more accuracy 
+    //but also larger possibility to fail 
+    my_time_client.setTimeout(800); 
+    Serial.println("syncing...");
+
+    while(my_time_client.update()!=1){
+        delay(2000);
+        my_time_client.forceUpdate();
+    }
+
+    Serial.print("success: ");
+    Serial.println(my_time_client.getFormattedTime());
+}
+
+void setup(){
+    Serial.begin(230400);
+    Serial.println("serial inited");
+
+    connect_wifi((char *)"ssid",(char *)"pwd");
+    sync_time();
+
+    Serial.println("ready!");
+}
+
+String s_last_time="s_last_time";
+
+void loop(){
+    String s_time=my_time_client.getFormattedTime();
+    if(s_time!=s_last_time){
+        Serial.print("a second passed ");
+        Serial.print(s_time);Serial.print(" ");
+        Serial.print(my_time_client.get_millis(),3);
+        Serial.println("ms");
+        s_last_time=s_time;
+
+        //please do not update too frequently
+        int8_t re=my_time_client.update();
+        if(re==0){
+            Serial.println("0: sync but failed");
+            delay(500);
+        }else if(re==1){
+            Serial.println("1: sync and suc");
+        }else if(re==2){
+            ;//Serial.println("2: not time to sync");
+        }else if(re==3){
+            Serial.println("3: last failed was just happen");
+        }else{
+            Serial.print("return value error: ");
+            Serial.println(re);
+        }
+    }
+
+    //float ms=my_time_client.get_millis();
+
+    delay(1);
+}