Programming oled display of the week day

Using Arduino Programming Questions
1

I have an interesting problem with my program which, is simply a modification of an example code for the DS3231 and a 128x64 OLED display. The code all runs smoothly except for the printing of the oled.print(daysOfTheWeek[now.dayOfTheWeek()]). It pulls the proper day with the first three letters but then appends the rest of the 3 letter array days for the rest of the week on to it.

EXAMPLE: THUFRISAT

I tried to use the (F(daysOfTheWeek[now.dayOfTheWeek())]); which I did not expect it to work but tried anyway.

Any Help would be greatly appreciated.

Hardware: Windows 10, Arduino IDE 1.8.15,
Sunfounder MEGA 2560
BN: Arduino Mega or Mega 2560
VID: 2341
PID: 0042
SN: 955303438343514062B1

#include "Adafruit_GFX.h"
#include "Adafruit_SSD1306.h"
#include "RTClib.h"

RTC_DS3231 rtc;
//char daysOfTheWeek[7][4] = {"SUN", "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY"};
char daysOfTheWeek[7][3] = {"SUN", "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY"};
// OLED display size in pixels
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

#define OLED_RESET -1
Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
DateTime now;

void setup() {
  Serial.begin(9600);
  delay(3000); // wait for console opening
  //rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  initializeRTC();
  initializeOLED();

}

void loop() {
  now = rtc.now();

  displayDay();  // ****Section where the issue is occuring
  displayDate();
  displayTime();
  displayTemperature();
}

void initializeRTC() {
  if (! rtc.begin()) {
    Serial.println("Couldn't find RTC");
    while (1);
  }

  if (rtc.lostPower()) {
    Serial.println("RTC lost power, lets set the time!");
    // following line sets the RTC to the date & time this sketch was compiled
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
    // This line sets the RTC with an explicit date & time, for example to set
    // January 21, 2014 at 3am you would call:
    // rtc.adjust(DateTime(2014, 1, 21, 3, 0, 0));
  }
}

void initializeOLED() {
  oled.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  oled.clearDisplay();
  oled.display();
  oled.setTextColor(WHITE, BLACK);
  oled.setTextSize(1);

  oled.setCursor(117, 55);
  // Enable the Code Page 437
  // https://en.wikipedia.org/wiki/Code_page_437
  oled.cp437(true);
  // Then print the chosen characters
  // which in this case is the degrees symbol
  // https://www.ascii-codes.com/
  oled.write(248);

  oled.setCursor(0, 55);
  oled.print("TEMPERATURE =");
  oled.setCursor(122, 55);
  oled.print("C");
}

void displayDay() {  // Function in which I believe the issue occurs
  oled.setTextSize(1);
  oled.setCursor(5, 15);
  oled.print(daysOfTheWeek[now.dayOfTheWeek()]);
  Serial.print(daysOfTheWeek[now.dayOfTheWeek()]);  //Placed in code for Troublshooting
  Serial.println();
}

void displayDate() {
  char currentDate [16];
  uint8_t thisDay, thisMonth ;
  thisDay = now.day();
  thisMonth = now.month();
  sprintf (currentDate, "%02d/%02d/", thisDay, thisMonth); //add leading zeros to the day and month

  oled.setTextSize(1);
  oled.setCursor(62, 15);
  oled.print(currentDate);

  oled.setTextSize(1);
  oled.setCursor(102, 15);
  oled.print(now.year(), DEC);
}

void displayTime() {
  char buffer [16];
  char AmPm[3];
  uint8_t thisSec, thisMin, thisHour;
  thisSec = now.second();
  thisMin = now.minute();
  thisHour = now.hour();

  if (thisHour > 12) {
    thisHour = thisHour - 12;
    strcpy(AmPm, "PM");
  } else strcpy(AmPm, "AM");

  sprintf (buffer, "%02d:%02d:%02d", thisHour, thisMin, thisSec);

  oled.setTextSize(2);
  oled.setCursor(6, 32);
  oled.print(buffer);

  oled.setTextSize(1);
  oled.setCursor(110, 32);
  oled.print(AmPm);
}

void displayTemperature() {
  oled.setTextSize(1);
  oled.setCursor(82, 55);
  oled.print(rtc.getTemperature());
  oled.display();
}
2

You can't use a print function on something that isn't a string.

char daysOfTheWeek[7][4]

Should fix it.

Obviously, you should limit the names to the initial three letters

3

@gdsmither, your topic has been moved to a more suitable location on the forum.

Thanks for using code tags in your first pist.

4

That worked. But I do not understand why it failed with the full names? Arn't they strings already?

5

What location was it moved too?

6

A three character string requires four bytes to store because you have to allow for the terminating zero.

7

OK that makes perfect sense.

Thanks it is always the little things that trip you up.

8

The compiler should have been giving you a warning about the string being too long to fit, but it likely scrolled off screen before you noticed.

9

Programming Questions. Installation and Troubleshooting is not for questions about your project :wink: See About the IDE 1.x category.

10

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