Creating a timestamp (RTClib)

Projects Programming
1

Hiya Community!

Atm i am working on my pool control unit and i do want to integrate a temp (DS1820) logging function (writing to flash in a ring buffer later).

I do have the RTC unit with a DS1307 and i am useing RTClib.
What i want to do is creating something like:

DD/MM hh:mm 26.4 ( where 26.4 is in °C)

what i do have so far is:

...
char TempBuf[10] = "         ";
char buffer[17];

dtostrf(PoolTemp, 4, 1, TempBuf);

sprintf(buffer,"%02i/%02i", now.day(), now.month());
Serial.println(buffer);

if i do continue it like:

...
char TempBuf[10] = "         ";
char buffer[17];

dtostrf(PoolTemp, 4, 1, TempBuf);

sprintf(buffer,"%02i/%02i %02i:%02i %04c", now.day(), now.month(), now.hour(), now.minute(), TempBuf);
Serial.println(buffer);

it freezes my arduino. Of course it has something to do with the parameters in sprintf but i don´t get it.

Your help is very much appreciated!
Cyber

2

** **char buffer[7];** **

seems a bit small :wink:

3

sorry, of course it meant to be 17...

i do have edited the post above :slight_smile: THX!

4

buffer is too small. It has to be big enough to accommodate all the characters you write to it in the sprintf call. Which means we count...

%02i - two characters
/ - one character
%02i - three (there is a trailing space there)
%02i - two
: - one
%02i - three (another space)
%04c - four

...16 (assuming I counted correctly). One extra for the "null terminator". Change the definition of buffer to this...

char buffer[17];
5

char Tempbuf[] has to be referred to as "%4s" in sprintf, I assume

6

Huge THANKS for all the help till now! Just great in here!

Version 1 (only day & month) is working. Even when only adding the statement for "hour" - i get freezed :slight_smile:

7

you need to provide (at least) as many parameters after the format, as "%" in the format string ...
( or you reverted to char buffer[7]; )

or some other simple mistake

%i or %d or %u should all be fine and equivalent for an unsigned decimal integer

Hm... try a test sketch with only

static char buffer[20];
sprintf(buffer, "%02u/%02u %02u:%02u", 6, 1, 23, 59);
Serial.println(buffer);
8

Thanks for the hint, but it freezes with that code too... :roll_eyes:

i do think it´s the code itself - anywhere else... i do change a bit of code anywhere and it gets freezed. At nearly 1000 lines of code, do you have any tip where to search first?

Cyber

9

I do have tracked it down to my logging function. If i do comment that function call out everything is working fine.

myBuffer1 or myBuffer2 is working, but not both at the same time - do you see a mistake?

complete code at: http://pastebin.com/Ju8feXYG

void LoggingValues()   // check if values have to be written to history
{
  DateTime now = RTC.now();
  
  int LastTimeSavedVal= 0;    // now.hour() of last time logging
  int PoolTempSavePosVal = 0;    // containing save position of ring logging buffer (value 0 to 8 = 9 values for logging - then reset)
  int iTempVal;
  unsigned int MinAddr = 0;    // calc memory position for writing actual Timestamp
     
  LastTimeSavedVal = EEPROM.read(LastTimeSaved);
  PoolTempSavePosVal = EEPROM.read(PoolTempSavePos);

  MinAddr = EEPROM_MIN_ADDR + PoolTempSavePosVal*BytesPerTempVal;

  for (iTempVal = 0; iTempVal < ValuesToLog; iTempVal++)
  {
    if (now.hour() >= (WakeUpTime + iTempVal*ValueLoggingIntervall) && LastTimeSavedVal < (WakeUpTime + iTempVal*ValueLoggingIntervall))    //calc if value has to be stored
    {
      getMedianTemps();    // reading temps from DS1820
  
      dtostrf(PoolTemp, 4, 1, TempBuf);    // convert float temperature for character operations
      
      PoolTempSavePosVal++;     
      if (PoolTempSavePosVal > 8)   // ring buffer reset
      {
        PoolTempSavePosVal = 0;
        //Serial.println("PoolTempSavePos Reset");
      }      
   
char myBuffer1[11];
sprintf(myBuffer1,"%02i/%02i %4s", now.day(), now.month(), TempBuf);
//Serial.println(myBuffer1); 

char myBuffer2[7];
sprintf(myBuffer2," %02i:%02i", now.hour(), now.minute());
//Serial.println(myBuffer2); 

     StringTemp = String(myBuffer1) + String(myBuffer2);
     StringTemp.toCharArray(TempChar, 18);    
      Serial.print("DEBUG WERT: ");      
      Serial.println(TempChar); 
...
10 
     StringTemp = String(myBuffer1) + String(myBuffer2);
     StringTemp.toCharArray(TempChar, 18);

Strings are bad, and + is a very expensive operator on Strings.
And I don't see the definition of TempChar...

What about just throwing that part away? :wink:
If you use it just for the Serial.println, either use the commented println's above instead, or setup your debug message in one sprintf() into a char array of sufficient size directly...

11

I am open of throwing it away :grin:
What i do want to get is a string / char array like:
06/01 12:00 26.4
which i could write to flash. (for example 3 times a day).

That + operation was trying a workaround because of the freezing when putting together all in one char array / a string. I will put it together char by char in one char array as u mentioned.

TempChar is globaly defined:

char TempChar[17] = "1234567890abcdef";