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Arduino库教程-WIfi无线扩展块101-UDP NTP Client

Arduino 少儿编程 573浏览 0评论
Arduino库教程

Network Time Protocol (NTP) Client

  • 在这个例子中,您将使用 WiFi Shield 101 和 Arduino 或者 Genuino Zero 开发板,来查询网络时间协议(NTP)服务器。这样,你的开发板可以从互联网上获得时间。

硬件要求

  • Arduino WiFi Shield 101
  • Arduino or Genuino Zero board
    或者
  • MKR1000

电路

  • 数字引脚7被用来作为WiFi Shield 101 和 开发板的握手引脚使用,而不应该被占用。
  • 这个例子里你应该进入一个连接到互联网的802.11b/g无线网络。你需要改变程序里的网络设置来符合您的特定网络SSID。

Arduino库教程-WIfi无线扩展块101-UDP NTP Client
图由 Fritzing 绘制
在上图,Arduino 或 Genuino Zero 开发板应该在堆叠在 WiFi shield上面。

样例代码

/*

 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,
 see http://en.wikipedia.org/wiki/Network_Time_Protocol

 created 4 Sep 2010
 by Michael Margolis
 modified 9 Apr 2012
 by Tom Igoe

 This code is in the public domain.

 */

#include <SPI.h>
#include <WiFi101.h>
#include <WiFiUdp.h>

int status = WL_IDLE_STATUS;
char ssid[] = "mynetwork";  //  your network SSID (name)
char pass[] = "mypassword";       // your network password
int keyIndex = 0;            // your network key Index number (needed only for WEP)

unsigned int localPort = 2390;      // local port to listen for UDP packets

IPAddress timeServer(129, 6, 15, 28); // time.nist.gov 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
WiFiUDP Udp;

void setup()
{
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  // check for the presence of the shield:
  if (WiFi.status() == WL_NO_SHIELD) {
    Serial.println("WiFi shield not present");
    // don't continue:
    while (true);
  }

  // attempt to connect to Wifi network:
  while ( status != WL_CONNECTED) {
    Serial.print("Attempting to connect to SSID: ");
    Serial.println(ssid);
    // Connect to WPA/WPA2 network. Change this line if using open or WEP network:
    status = WiFi.begin(ssid, pass);

    // wait 10 seconds for connection:
    delay(10000);
  }

  Serial.println("Connected to wifi");
  printWifiStatus();

  Serial.println("nStarting connection to server...");
  Udp.begin(localPort);
}

void loop()
{
  sendNTPpacket(timeServer); // send an NTP packet to a time server
  // wait to see if a reply is available
  delay(1000);
  if ( Udp.parsePacket() ) {
    Serial.println("packet received");
    // We've received a packet, read the data from it
    Udp.read(packetBuffer, 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, esxtract 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 = " );
    Serial.println(secsSince1900);

    // 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:
    Serial.println(epoch);


    // 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)
    Serial.print(':');
    if ( ((epoch % 3600) / 60) < 10 ) {
      // In the first 10 minutes of each hour, we'll want a leading '0'
      Serial.print('0');
    }
    Serial.print((epoch  % 3600) / 60); // print the minute (3600 equals secs per minute)
    Serial.print(':');
    if ( (epoch % 60) < 10 ) {
      // In the first 10 seconds of each minute, we'll want a leading '0'
      Serial.print('0');
    }
    Serial.println(epoch % 60); // print the second
  }
  // wait ten seconds before asking for the time again
  delay(10000);
}

// send an NTP request to the time server at the given address
unsigned long sendNTPpacket(IPAddress& address)
{
  //Serial.println("1");
  // 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)
  //Serial.println("2");
  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;

  //Serial.println("3");

  // 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
  //Serial.println("4");
  Udp.write(packetBuffer, NTP_PACKET_SIZE);
  //Serial.println("5");
  Udp.endPacket();
  //Serial.println("6");
}


void printWifiStatus() {
  // print the SSID of the network you're attached to:
  Serial.print("SSID: ");
  Serial.println(WiFi.SSID());

  // print your WiFi shield's IP address:
  IPAddress ip = WiFi.localIP();
  Serial.print("IP Address: ");
  Serial.println(ip);

  // print the received signal strength:
  long rssi = WiFi.RSSI();
  Serial.print("signal strength (RSSI):");
  Serial.print(rssi);
  Serial.println(" dBm");
}

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更多

  • WiFi library – WiFi101 库的参考网页
  • WiFi Shield – WiFi 扩展板 101 的产品细节
  • MKR1000 – MKR1000 板的产品细节
  • Connect No Encryption: 演示如何连接到一个开放的网络。
  • Connect With WEP: 演示如何连接到用WEP加密的网络。
  • Connect With WPA: 演示如何连接到一个用WPA2个人加密网络。
  • Scan Networks:显示出所有在范围内的无线网络。
  • Simple Web Server WiFi: 通过打开和关闭一个LED来访问这个简单的Web服务器
  • UDP NTP Client: 通过UDP查询网络时间协议(NTP)服务器。
  • WiFi Chat Server: 建立一个简单的聊天服务器。
  • WiFi Web Client: 连接到一个远程服务器。
  • WiFi Web Client Repeating: 反复做HTTP请求到服务器。
  • WiFi Web Server: 通过模拟输入值来服务一个来自WIfi无线扩展块的网页。
  • WiFi Send Receive UDP String: 发送和接收UDP字符串。

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