Arduino TimeAlarms are not working sometimes

Question

i use an Arduino Mega compatible board (SainSmart Mega 2560 R3 ATmega2560-16AU) which has a rtc module attached (v1.1 ds1307rtc) and working on it with the attached code. I have used the TimeAlarms library (downloaded it from http://www.pjrc.com/teensy/td_libs_TimeAlarms.html) to have an alarm every hour. The alarms should occur at different minutes every hour, but for testing i have set them all to the 12th minute. This code is waiting for a correct time, which i can set via usb, serial interface. The code is working fine most of the times. But sometimes the alarm is not activated and my leds are not flashing. I don't know why and when this happens, i didn't any changes between the working flashing and not working. Also i can't see any hours where it doesn't working correct, afaik it works correct, but fails sometimes. If it failes, it looks like all hours after the failing hour are also failing and no alarm is triggered. I know about the restriction of 6 alarms in TimeAlarms.h and set the variable dtNBR_ALARMS in this file to 25.

As you can see i have implemented a printTime function which print out the rtc and the system time and always both are correct.

Has anyone an idea what i am doing wrong or why it fails sometimes?

#include <Time.h>
#include <TimeAlarms.h>
#include <Wire.h>
#include <DS1307RTC.h>

tmElements_t tm;

int pwm_2 = 2;
int pwm_3 = 3;
int pwm_4 = 4;
int pwm_5 = 5;
int pwm_6 = 6;
int pwm_7 = 7;
int pwm_8 = 8;
int pwm_9 = 9;
int pwm_10 = 10;
int pwm_11 = 11;
int pwm_12 = 12;
int pwm_13 = 13;
//delay in the for loops
int dly = 120;

// the setup routine runs once when you press reset:
void setup()  { 
  Serial.begin(9600);
  while (!Serial) ; // wait for serial
  setSyncProvider(RTC.get);   // the function to get the time from the RTC
  RTC.read(tm);
  setTime(tm.Hour,tm.Minute,tm.Second,tm.Day,tm.Month,tm.Year);
  printTime();

  //wait for time input via serial, time must be set at every system boot
  while(tmYearToCalendar(tm.Year) < 2014) {
    Serial.println("wait in time loop, you have to set a time, current time is not correct:");
    printTime();
    if (Serial.available()) {
      time_t t = processSyncMessage();
      Serial.println("wait in time loop");
      if (t != 0) {
        RTC.set(t);   // set the RTC and the system time to the received value
        setTime(t); 
        Serial.println("time is succesfully set to");
        printTime(); 
        break;        
      }
    }
    delay(1000);
  }
  Serial.println("Time is already set to:");
  printTime();

  //set alarms for all hours in UTC, not in CET
  Alarm.alarmRepeat(0, 12, 0, shotAlarm);
  Alarm.alarmRepeat(1, 12, 0, shotAlarm);
  Alarm.alarmRepeat(2, 12, 0, shotAlarm);
  Alarm.alarmRepeat(3, 12, 0, shotAlarm);
  Alarm.alarmRepeat(4, 12, 0, shotAlarm);
  Alarm.alarmRepeat(5, 12, 0, shotAlarm);
  Alarm.alarmRepeat(6, 12, 0, shotAlarm);
  Alarm.alarmRepeat(7, 12, 0, shotAlarm);
  Alarm.alarmRepeat(8, 12, 0, shotAlarm);
  Alarm.alarmRepeat(9, 12, 0, shotAlarm);
  Alarm.alarmRepeat(10, 12, 0, shotAlarm);
  Alarm.alarmRepeat(11, 12, 0, shotAlarm);
  Alarm.alarmRepeat(12, 12, 0, shotAlarm);
  Alarm.alarmRepeat(13, 12, 0, shotAlarm);
  Alarm.alarmRepeat(14, 12, 0, shotAlarm);
  Alarm.alarmRepeat(15, 12, 0, shotAlarm);
  Alarm.alarmRepeat(16, 12, 0, shotAlarm);
  Alarm.alarmRepeat(17, 12, 0, shotAlarm);
  Alarm.alarmRepeat(18, 12, 0, shotAlarm);
  Alarm.alarmRepeat(19, 12, 0, shotAlarm);
  Alarm.alarmRepeat(20, 12, 0, shotAlarm);
  Alarm.alarmRepeat(21, 12, 0, shotAlarm);
  Alarm.alarmRepeat(22, 12, 0, shotAlarm);
  Alarm.alarmRepeat(23, 12, 0, shotAlarm);

  // declare pin 2-13 to be an output:
  pinMode(pwm_2, OUTPUT); //red
  pinMode(pwm_3, OUTPUT); //blue
  pinMode(pwm_4, OUTPUT); //green
  pinMode(pwm_5, OUTPUT);  //red
  pinMode(pwm_6, OUTPUT); //blue
  pinMode(pwm_7, OUTPUT);  //green
  pinMode(pwm_8, OUTPUT);  //red
  pinMode(pwm_9, OUTPUT); //blue
  pinMode(pwm_10, OUTPUT);  //green
  pinMode(pwm_11, OUTPUT); //red
  pinMode(pwm_12, OUTPUT);  //blue
  pinMode(pwm_13, OUTPUT);  //green  
} 

void shotAlarm() {
  Serial.println("SHOTALARM");
  analogWrite(pwm_2, 255);
  analogWrite(pwm_5, 255);
  analogWrite(pwm_8, 255);
  analogWrite(pwm_11, 255);
  analogWrite(pwm_3, 255); 
  analogWrite(pwm_4, 255); 
  analogWrite(pwm_6, 255); 
  analogWrite(pwm_7, 255); 
  analogWrite(pwm_9, 255);
  analogWrite(pwm_10, 255); 
  analogWrite(pwm_12, 255); 
  analogWrite(pwm_13, 255); 
  for(int a = 0; a < 60; a = a+1) {
    for (int i = 0; i < 255; i = i + 1) {
      analogWrite(pwm_2, i); //red
      analogWrite(pwm_5, i); //red
      analogWrite(pwm_8, i); //red
      analogWrite(pwm_11, i); //red
      delay (5);
    }
    for (int i = 255; i > 0; i = i - 1) {
      analogWrite(pwm_2, i); //red
      analogWrite(pwm_5, i); //red
      analogWrite(pwm_8, i); //red
      analogWrite(pwm_11, i); //red
      delay (5);
    }
  }
}
void loop() {
  Alarm.delay(0);
  Serial.println("new loop");
  printTime();
  analogWrite(pwm_2, 0);
  analogWrite(pwm_5, 0);
  analogWrite(pwm_8, 0);
  analogWrite(pwm_11, 0);
  analogWrite(pwm_3, 255); 
  analogWrite(pwm_4, 255); 
  analogWrite(pwm_6, 255); 
  analogWrite(pwm_7, 255); 
  analogWrite(pwm_9, 255);
  analogWrite(pwm_10, 255); 
  analogWrite(pwm_12, 255); 
  analogWrite(pwm_13, 255); 
  for (int i = 255; i > 0; i = i - 1) {
    analogWrite(pwm_4, i); //green
    analogWrite(pwm_7, i); //green
    analogWrite(pwm_10, i); //green
    analogWrite(pwm_13, i); //green  
    Alarm.delay (dly);
  }
  for (int i = 0; i < 255; i = i + 1) {
    analogWrite(pwm_2, i); //red
    analogWrite(pwm_5, i); //red
    analogWrite(pwm_8, i); //red
    analogWrite(pwm_11, i); //red
    Alarm.delay (dly);
  } 
  for (int i = 255; i > 0; i = i - 1) {
    analogWrite(pwm_3, i); //blue
    analogWrite(pwm_6, i); //blue
    analogWrite(pwm_9, i); //blue
    analogWrite(pwm_12, i); //blue      
    Alarm.delay (dly);
  }
  for (int i = 0; i < 255; i = i + 1) {
    analogWrite(pwm_4, i); //green
    analogWrite(pwm_7, i); //green
    analogWrite(pwm_10, i); //green
    analogWrite(pwm_13, i); //green  
    Alarm.delay (dly);
  }  
  for (int i = 255; i > 0; i = i - 1) {
    analogWrite(pwm_2, i); //red
    analogWrite(pwm_5, i); //red
    analogWrite(pwm_8, i); //red
    analogWrite(pwm_11, i); //red
    Alarm.delay (dly);
  }
  for (int i = 0; i < 255; i = i + 1) {
    analogWrite(pwm_3, i); //blue
    analogWrite(pwm_6, i); //blue
    analogWrite(pwm_9, i); //blue
    analogWrite(pwm_12, i); //blue 
    Alarm.delay (dly);
  }
  Alarm.delay(0);
}

void printTime() {
  if (RTC.read(tm)) {
    Serial.print("Ok, RTC Time = ");
    print2digits(tm.Hour);
    Serial.write(':');
    print2digits(tm.Minute);
    Serial.write(':');
    print2digits(tm.Second);
    Serial.print(", Date (D/M/Y) = ");
    Serial.print(tm.Day);
    Serial.write('/');
    Serial.print(tm.Month);
    Serial.write('/');
    Serial.print(tmYearToCalendar(tm.Year));
    Serial.println();
  } 
  else {
    if (RTC.chipPresent()) {
      Serial.println("The DS1307 is stopped.  Please run the SetTime");
      Serial.println("example to initialize the time and begin running.");
      Serial.println();
    } 
    else {
      Serial.println("DS1307 read error!  Please check the circuitry.");
      Serial.println();
    }
  }
  Serial.print("Ok, System Time = ");
  print2digits(hour());
  Serial.write(':');
  print2digits(minute());
  Serial.write(':');
  print2digits(second());
  Serial.print(", Date (D/M/Y) = ");
  Serial.print(day());
  Serial.write('/');
  Serial.print(month());
  Serial.write('/');
  Serial.print(year());
  Serial.println();
}
void print2digits(int number) {
  if (number >= 0 && number < 10) {
    Serial.write('0');
  }
  Serial.print(number);
}
/*  code to process time sync messages from the serial port   */
#define TIME_HEADER  "T"   // Header tag for serial time sync message
unsigned long processSyncMessage() {
  unsigned long pctime = 0L;
  const unsigned long DEFAULT_TIME = 1357041600; // Jan 1 2013 

  if(Serial.find(TIME_HEADER)) {
    pctime = Serial.parseInt();
    return pctime;
    if( pctime < DEFAULT_TIME) { // check the value is a valid time (greater than Jan 1 2013)
      pctime = 0L; // return 0 to indicate that the time is not valid
    }
  }
  return pctime;
}

Answer 1

For all who read this thread later: I found the mistake in my code. The following line was wrong:

setTime(tm.Hour,tm.Minute,tm.Second,tm.Day,tm.Month,tm.Year);

The correct version is:

setTime(tm.Hour,tm.Minute,tm.Second,tm.Day,tm.Month,tmYearToCalendar(tm.Year));

Unfortunately i forgot to convert the year value to the expected format. The code from above is working very fine with this correction. I checked the alarms for more then a week and it is working very stable.

Thanks all for their help.

Answer 2

One thing to mention is that in the read me of the TimerAlarm library, it says you can only define up to 6 alarms only, but that can be changed inside the library by dtNBR_ALARMS field. The number ofcourse is restricted by ram but you can easily add that since the Arduino mega has a significantly large SRAM. So this might be worth looking at if you experience further problems with the alarms.