使用Arduino+网络扩展板和一个lcd1602来制作,每20s使用NTP同步一次时间,所以绝对无误差,不过必须要在又网络的地方才能用。
首先会尝试使用DHCP来自动获取ip,如果失败则使用静态ip。
别的不多说了,直接上代码:
#include <LiquidCrystal.h> #include <SPI.h> #include <Ethernet.h> #include <EthernetUdp.h> int RS=49; int RW=47; int E =45; int DB4=35; int DB5=33; int DB6=31; int DB7=29; unsigned long epoch; byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; unsigned int localPort = 8888; // local port to listen for UDP packets char timeServer[] = "time.nist.gov"; // 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 EthernetUDP Udp; IPAddress static_ip(192,168,1,177); LiquidCrystal lcd(RS, E, DB4, DB5, DB6, DB7); void setup() { pinMode(27, OUTPUT); //LDE + pinMode(25, OUTPUT); //LDE - pinMode(53, OUTPUT); //VCC pinMode(51, OUTPUT); //V0 pinMode(RS, OUTPUT); //RS pinMode(RW, OUTPUT); //RW pinMode(E , OUTPUT); //E digitalWrite(27, HIGH); digitalWrite(25, LOW); digitalWrite(53, HIGH); digitalWrite(51, LOW); digitalWrite(RW, LOW); // Open serial communications and wait for port to open: Serial.begin(9600); lcd.begin(16, 2); lcd.blink(); Serial.println("1602 NTP Clock"); Serial.print("Trying to configure Ethernet using DHCP..."); lcd.print("1602 NTP Clock"); lcd.setCursor(0,1); lcd.print("Trying DHCP..."); if (Ethernet.begin(mac) == 0){ Serial.println("Failed"); Serial.println("Use static IP"); Ethernet.begin(mac, static_ip); }else{ Serial.println("Success"); } Serial.print("Arduino`s IP is "); Serial.println(Ethernet.localIP()); lcd.clear(); lcd.home(); lcd.print("Arduino`s IP is "); lcd.setCursor(2,1); lcd.print(Ethernet.localIP()); Udp.begin(localPort); sendNTPpacket(timeServer); delay(1000); processNTPpacket(); lcd.clear(); } void loop() { int i; for(i=0;i<19;i++){ displayTheTime(); delay(1000); epoch+=1; } displayTheTime(); sendNTPpacket(timeServer); delay(1000); processNTPpacket(); } // send an NTP request to the time server at the given address void sendNTPpacket(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); Udp.endPacket(); } void processNTPpacket(){ if (Udp.parsePacket()) { // 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, 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; // 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: epoch = secsSince1900 - seventyYears + 1; // print Unix time: Serial.println(epoch); } } void displayTheTime(){ lcd.home(); lcd.print('%'); lcd.print(epoch); // print the hour, minute and second: lcd.setCursor(0,1); lcd.print((epoch % 86400L) / 3600); // print the hour (86400 equals secs per day) lcd.print(':'); if (((epoch % 3600) / 60) < 10) { // In the first 10 minutes of each hour, we'll want a leading '0' lcd.print('0'); } lcd.print((epoch % 3600) / 60); // print the minute (3600 equals secs per minute) lcd.print(':'); if ((epoch % 60) < 10) { // In the first 10 seconds of each minute, we'll want a leading '0' lcd.print('0'); } lcd.print(epoch % 60); // print the second lcd.setCursor(15,1); }