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Thread: Teensy 3.6 + wiz820io NTP example problem

  1. #1

    Teensy 3.6 + wiz820io NTP example problem

    Hello everyone!

    I'm havingsome problems with the NTP example. If I use the provided example everything works fine. The sketch sends a UDP request to the time server and I get a correct response.

    But if I assign a fixed IP it stps working even if I assign the same IP that the router has provided me before when I used the provided example

     Udp NTP Client
     Get the time from a Network Time Protocol (NTP) time server
     Demonstrates use of UDP sendPacket and ReceivePacket
     For more on NTP time servers and the messages needed to communicate with them,
     created 4 Sep 2010
     by Michael Margolis
     modified 9 Apr 2012
     by Tom Igoe
     modified 02 Sept 2015
     by Arturo Guadalupi
     This code is in the public domain.
    #include <SPI.h>
    #include <Ethernet.h>
    #include <EthernetUdp.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[] = {
      0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
    IPAddress ip(192, 168, 0, 177);
    unsigned int localPort = 8888;       // local port to listen for UDP packets
    const char timeServer[] = ""; // NTP server
    const int NTP_PACKET_SIZE = 48; // NTP time stamp is in the first 48 bytes of the message
    byte packetBuffer[NTP_PACKET_SIZE]; //buffer to hold incoming and outgoing packets
    // A UDP instance to let us send and receive packets over UDP
    EthernetUDP Udp;
    void setup() {
      // You can use Ethernet.init(pin) to configure the CS pin
      Ethernet.init(10);  // Most Arduino shields
      //Ethernet.init(5);   // MKR ETH shield
      //Ethernet.init(0);   // Teensy 2.0
      //Ethernet.init(20);  // Teensy++ 2.0
      //Ethernet.init(15);  // ESP8266 with Adafruit Featherwing Ethernet
      //Ethernet.init(33);  // ESP32 with Adafruit Featherwing Ethernet
      // Open serial communications and wait for port to open:
      while (!Serial) {
        ; // wait for serial port to connect. Needed for native USB port only
      // start Ethernet and UDP
      //Ethernet.begin(mac); // <------------- THIS WORKS
      Ethernet.begin(mac, ip); // <------------- THIS  DOES NOT WORK
    void loop() {
      sendNTPpacket(timeServer); // send an NTP packet to a time server
      // wait to see if a reply is available
      if (Udp.parsePacket()) {
        // We've received a packet, read the data from it, NTP_PACKET_SIZE); // read the packet into the buffer
        // the timestamp starts at byte 40 of the received packet and is four bytes,
        // or two words, long. First, extract the two words:
        unsigned long highWord = word(packetBuffer[40], packetBuffer[41]);
        unsigned long lowWord = word(packetBuffer[42], packetBuffer[43]);
        // 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;
        Serial.print("Seconds since Jan 1 1900 = ");
        // now convert NTP time into everyday time:
        Serial.print("Unix time = ");
        // Unix time starts on Jan 1 1970. In seconds, that's 2208988800:
        const unsigned long seventyYears = 2208988800UL;
        // subtract seventy years:
        unsigned long epoch = secsSince1900 - seventyYears;
        // print Unix time:
        // print the hour, minute and second:
        Serial.print("The UTC time is ");       // UTC is the time at Greenwich Meridian (GMT)
        Serial.print((epoch  % 86400L) / 3600); // print the hour (86400 equals secs per day)
        if (((epoch % 3600) / 60) < 10) {
          // In the first 10 minutes of each hour, we'll want a leading '0'
        Serial.print((epoch  % 3600) / 60); // print the minute (3600 equals secs per minute)
        if ((epoch % 60) < 10) {
          // In the first 10 seconds of each minute, we'll want a leading '0'
        Serial.println(epoch % 60); // print the second
      // wait ten seconds before asking for the time again
    // send an NTP request to the time server at the given address
    void sendNTPpacket(const char * address) {
      // set all bytes in the buffer to 0
      memset(packetBuffer, 0, NTP_PACKET_SIZE);
      // Initialize values needed to form NTP request
      // (see URL above for details on the packets)
      packetBuffer[0] = 0b11100011;   // LI, Version, Mode
      packetBuffer[1] = 0;     // Stratum, or type of clock
      packetBuffer[2] = 6;     // Polling Interval
      packetBuffer[3] = 0xEC;  // Peer Clock Precision
      // 8 bytes of zero for Root Delay & Root Dispersion
      packetBuffer[12]  = 49;
      packetBuffer[13]  = 0x4E;
      packetBuffer[14]  = 49;
      packetBuffer[15]  = 52;
      // all NTP fields have been given values, now
      // you can send a packet requesting a timestamp:
      Udp.beginPacket(address, 123); // NTP requests are to port 123
      Udp.write(packetBuffer, NTP_PACKET_SIZE);
    So if I change Ethernet.begin(mac); to Ethernet.begin(mac, ip); the sketch does not work but I can ping the Teensy and even send fake UDP packets to it without any problem...

    Is this a bug or an router issue?

    Thank you!

  2. #2
    Senior Member+ manitou's Avatar
    Join Date
    Jan 2013
    if you kept the MAC address the same when flipping between fixed IP and DHCP, then you may have ARP problems at other hosts/routers, because they have ARP address indexed by the MAC address. Try using different MAC address for fixed vs DHCP

  3. #3
    I fixed it!
    After some digging I noticed that my setup was incomplete.. I was only assigning the mac and IP... I needed to assign gateway, subnet and DNS... So the teensy can access the outside world ... Stupid me!!

    Ethernet.begin(mac, ip, dns, gateway, subnet);
    Thank you anyway for taking you time to help me!

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