D1307 Time.h lib: weekday() always returning Thursday

Projects Programming
1

Hello,

I am new to Arduino. I am using a D1307 connected with my Arduino and I am trying to extract the day of the week (e.g. Monday). My code:

//www.elegoo.com
//2018.10.24
#include <Wire.h>
#include <DS3231.h>
#include <TimeLib.h>
DS3231 clock;
RTCDateTime dt;
int dayOfWeek;

void setup()
{
  Serial.begin(9600);

  Serial.println("Initialize RTC module");
  // Initialize DS3231
  clock.begin();

  
  // Manual (YYYY, MM, DD, HH, II, SS
  // clock.setDateTime(2016, 12, 9, 11, 46, 00);
  
  // Send sketch compiling time to Arduino
  clock.setDateTime(__DATE__, __TIME__);    
  /*
  Tips:This command will be executed every time when Arduino restarts. 
       Comment this line out to store the memory of DS3231 module
  */
}

void loop()
{
  dt = clock.getDateTime(); // dt is object of class RTCDateTime

  // For leading zero look to DS3231_dateformat example

  Serial.print("Raw data: ");
  Serial.print(dt.year);   Serial.print("-");
  Serial.print(dt.month);  Serial.print("-");
  Serial.print(dt.day);    Serial.print(" ");
  Serial.print(dt.hour);   Serial.print(":");
  Serial.print(dt.minute); Serial.print(":");
  Serial.print(dt.second); Serial.println("");

  dayOfWeek = weekday();
  
  Serial.print(dayStr(dayOfWeek)); Serial.println("");

  delay(1000);
}

Which returns:

Raw data: 2021-9-18 12:30:34
Thursday

where I would expect Saturday.

Apparently I am not using the weekday() correctly, but apparently it does not need any arguments so I am not sure how it could extract the day in the week from e.g. my RTCDateTime object.

Many thanks.

2

Try

dayOfWeek = dt.Wday;
3 
Electricity_Timer:46:18: error: 'struct RTCDateTime' has no member named 'Wday'; did you mean 'day'?

I am using DS3231 v1.0.7; should I update?

4

There is no perpetual calendar in the RTC.

You have to set the day, it will increment daily.

Set your time to just before midnight and watch the day change…

a7

5

Sorry, my bad

dayOfWeek = dt.wday;
6 
Electricity_Timer:46:18: error: 'struct RTCDateTime' has no member named 'wday'; did you mean 'day'?
7

You can use functions in the TimeLib to act as a perpetual calendar, but the way you are setting the time does not automagically calculate the day of week.

a7

8

Use the full setDateTime call, viz:

    setDateTime(uint16_t year, uint8_t month, uint8_t day, uint8_t hour, uint8_t minute, uint8_t second);

This lets you set all the registers. use a day value from 1 to 7 inclusive.

If you set it manually to just before midnight, you can then disable the setting (comment out the setDateTime call). Run your program a few minutes later and the day will have incremented.

a7

9

Please provide links the libraries you are using. There are several with the same name but different syntax.

10

@cattledog There are several with the same name but different syntax.

True that. This is the one I found that seems like a match, at least the code will compile where the library I had installed did not.

The OP’s code compiles. And as far as I can tell, functions correctly.

To get the day of week by algorithm from the TimeLib takes a few steps it seems.

I’ve just alway set the day myself. I use Sunday == 1, so.

HTH

a7

11

OK, you mixing up TImeLib and DS3231 libraries somehow.

Change

  dayOfWeek = weekday();
  
  Serial.print(dayStr(dayOfWeek)); Serial.println("");

to

//  dayOfWeek = weekday();
  
  Serial.print(dayStr(dt.dayOfWeek)); Serial.println("");

and leave TimeLib's weekday() out of it. Didn't you notice the first day printed was "Err", not any Sunday through Saturday? That was my clue to go looking…

Just pass the RTC's dt.dayOfWeek to dayStr.

And now I can say that the DS3231 library has a Zeller's congruence algorithm, so it does, in fact, set the day of week correctly for use with dayStr.

dayStr is the only thing you are using from TimeLib it seems.

HTH

a7

12

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