Arduino, fammi il caffè! V0.1

Ho raggiunto i primi due obiettivi che mi ero posto con l’Arduino, ovvero

1. prendere l’ora da internet tramite il Net Time Protocol
2. accendere la macchina del caffè all’ora prefissata

Ma non è finita: adesso bisogna (bisogna!) che l’ora di accensione venga impostata via web, non inserita banalmente a mano nel codice. Per fare questo occorre che sia contemporaneamente attivo il cliente NTP e il server web, e grosse nubi si addensano sul mio orizzonte di entusiasta ignorante.

Inoltre non è bello che l’Arduino debba autisticamente chiedere l’ora a NTP ogni minuto: meglio sarebbe se chiedesse solo una volta al giorno per sincronizzare con un suo orologio interno.

Come dire che ho le sere impegnate fino a primavera. Il codice fino a questo punto, dopo il salto: come sempre, eventuali commenti, critiche e suggerimenti sono molto bene accetti.

/*
 Arduino, fammi il caffè! V.0.1
 
 created 4 Sep 2010 
 by Michael Margolis
 modified 17 Sep 2010
 by Tom Igoe
 modified 18 Feb 2012
 by Gaspar Torriero
 
 This code is in the public domain.

 */

#include <SPI.h>
#include <Ethernet.h>
#include <EthernetUdp.h>

int cHH; // current hour
int cMM; // current minute
int cSS; // current second
int outPin = 8; // connected to coffee machine via relè

// Enter a MAC address for your controller below
byte mac[] = {
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };

unsigned int localPort = 8888;      // local port to listen for UDP packets

IPAddress timeServer(192, 43, 244, 18); // 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;

void setup()
{
  // Serial.begin(9600); // uncomment for testing
  digitalWrite(outPin, LOW);

  // start Ethernet and UDP
  if (Ethernet.begin(mac) == 0) {
    // Serial.println("Failed to configure Ethernet using DHCP"); // uncomment for testing
    // no point in carrying on, so do nothing forevermore:
    for(;;)
      ;
  }
  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() ) {
    // 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;  

    // 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 the hour, minute and second:
    cHH = (epoch  % 86400L) / 3600 + 1;
    cMM = (epoch  % 3600) / 60;
    cSS = epoch %60;

    /* uncomment for testing
    Serial.print("Local time is ");
    Serial.print(cHH);
    Serial.print(" hours, ");
    Serial.print(cMM);
    Serial.print(" minutes, and ");
    Serial.print(cSS);
    Serial.println(" seconds.");
    */

    // Turns on the coffee machine
    // at a fixed time.
    // Next goal: set time via web.
    if((cHH == 6) && (cMM > 44)) {
      digitalWrite(outPin, HIGH);
    }
  }
  // wait 60 seconds before asking for the time again
  // Next goal: let Arduino Keep the time
  // and synchronize daily.

  delay(60000); 

}

// send an NTP request to the time server at the given address 
unsigned long sendNTPpacket(IPAddress& 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();
}