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RTC Alarm

The onboard RTC supports creating an alarm that triggers at a specific time, allowing the firmware to detect and respond accordingly. Alarms can be configured to trigger once per day, per hour, or per minute.

Simple alarm​

This section demonstrates setting a simple RTC alarm that is checked using polling. The firmware continuously checks the alarm flag and responds when it is triggered.

#include "Inkplate.h"            // Include Inkplate library to the sketch
Inkplate inkplate(INKPLATE_1BIT); // Create an object on Inkplate library and also set library into 1-bit mode (BW)

#define REFRESH_DELAY 1000 // Delay between refreshes
unsigned long time1;       // Time for measuring refresh in millis

// Set clock
uint8_t hour = 12;
uint8_t minutes = 50;
uint8_t seconds = 30;

// Set date and weekday (NOTE: In weekdays 0 means Sunday, 1 means Monday, ...)
uint8_t weekday = 1;
uint8_t day = 20;
uint8_t month = 2;
uint8_t year = 23;

// Set alarm time and date (alarm will be generated 10 seconds after board power up)
uint8_t alarmHour = 12;
uint8_t alarmMinutes = 50;
uint8_t alarmSeconds = 40;
uint8_t alarmWeekday = 1;
uint8_t alarmDay = 20;

void setup()
{
    inkplate.begin();        // Init Inkplate library (you should call this function ONLY ONCE)
    inkplate.clearDisplay(); // Clear frame buffer of inkplate
    inkplate.display();      // Put clear image on inkplate
    inkplate.setTextSize(5); // Set text to be 5 times bigger than classic 5x7 px text

    inkplate.rtcSetTime(hour, minutes, seconds);                                         // Send time to RTC
    inkplate.rtcSetDate(weekday, day, month, year);                                      // Send date to RTC
    inkplate.rtcSetAlarm(alarmSeconds, alarmMinutes, alarmHour, alarmDay, alarmWeekday); // Set alarm
}

// Variable that keeps count on how much screen has been partially updated
int n = 0;
void loop()
{
    if ((unsigned long)(millis() - time1) > REFRESH_DELAY)
    {
        inkplate.rtcGetRtcData();           // Get the time and date from RTC
        seconds = inkplate.rtcGetSecond();  // Store seconds in a variable
        minutes = inkplate.rtcGetMinute();  // Store minutes in a variable
        hour = inkplate.rtcGetHour();       // Store hours in a variable
        day = inkplate.rtcGetDay();         // Store day of month in a variable
        weekday = inkplate.rtcGetWeekday(); // Store day of week in a variable
        month = inkplate.rtcGetMonth();     // Store month in a variable
        year = inkplate.rtcGetYear();       // Store year in a variable

        inkplate.clearDisplay();                                       // Clear content in frame buffer
        inkplate.setCursor(100, 300);                                  // Set position of the text
        printTime(hour, minutes, seconds, day, weekday, month, year); // Print the time on screen

        if (inkplate.rtcCheckAlarmFlag()) // Check if alarm has occurred
        {
            inkplate.rtcClearAlarmFlag(); // It's recommended to clear alarm flag after alarm has occurred
            inkplate.setCursor(400, 400); // Set new position for cursor
            inkplate.print("ALARM!");
        }

        if (n > 9) // Check if you need to do full refresh or you can do partial update
        {
            inkplate.display(true); // Do a full refresh
            n = 0;
        }
        else
        {
            inkplate.partialUpdate(false, true); // Do partial update and keep e-paper power supply on
            n++;                                // Keep track on how many times screen has been partially updated
        }

        time1 = millis(); // Store current millis
    }
}

void printTime(uint8_t _hour, uint8_t _minutes, uint8_t _seconds, uint8_t _day, uint8_t _weekday, uint16_t _month,
               uint8_t _year)
{
    // Write time and date info on screen
    char *wday[] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};

    print2Digits(_hour);
    inkplate.print(':');
    print2Digits(_minutes);
    inkplate.print(':');
    print2Digits(_seconds);

    inkplate.print(' ');

    inkplate.print(wday[_weekday]);
    inkplate.print(", ");
    print2Digits(_day);
    inkplate.print('/');
    print2Digits(_month);
    inkplate.print('/');
    inkplate.print(_year, DEC);
}

void print2Digits(uint8_t _d)
{
    if (_d < 10)
        inkplate.print('0');
    inkplate.print(_d, DEC);
}

inkplate.rtcSetAlarm()

Sets the alarm to all the parameters.

Returns type: void

Function parameters:

TypeNameDescription
uint8_trtcAlarmSecondSet the alarm seconds.
uint8_trtcAlarmminuteSet the alarm minutes.
uint8_trtcAlarmHourSet the alarm hours.
uint8_trtcAlarmDaySet the alarm rtcDay.
uint8_trtcAlarmWeekdaySet the alarm rtcWeekday.

inkplate.rtcCheckAlarmFlag()

Checks if the alarm flag is on

Returns type: bool

Returns value: Returns true if the alarm flag is on

Interrupt Alarm​

The RTC alarm can also generate an interrupt instead of requiring polling. The alarm event can wake up the MCU from sleep or trigger an action immediately. To use this, you will need to globally declare a volatile bool to use as the alarm flag and a function that modifies this flag:

#include "Inkplate.h"             // Include Inkplate library to the sketch
Inkplate inkplate(INKPLATE_1BIT);  // Create an object on Inkplate library and also set library into 1-bit mode (BW)

volatile int _alarmFlag = 0;      // Variable to store alarm flag

void IRAM_ATTR alarmISR()         // This function will be called when alarm interrupt event happens
{                                 // NOTE: Function must be above setup() and loop()!
  _alarmFlag = 1;                 // Set alarm flag
}

void setup()
{
    pinMode(39, INPUT_PULLUP);      // Set RTC INT pin on ESP32 GPIO39 as input with pullup resistor enabled

    inkplate.begin();        // Init Inkplate library (you should call this function ONLY ONCE)
    inkplate.clearDisplay(); // Clear frame buffer of inkplate
    inkplate.display();      // Put clear image on inkplate
    inkplate.setTextSize(5); // Set text to be 5 times bigger than classic 5x7 px text
  
    inkplate.rtcSetEpoch(1589610300);
    inkplate.rtcSetAlarmEpoch(inkplate.rtcGetEpoch() + 10, RTC_ALARM_MATCH_DHHMMSS);

    // inkplate.rtcSetTime(6, 25, 0);        // Or you can use other way to set the time and date
    // inkplate.rtcSetDate(6, 16, 5, 2020);
    // inkplate.rtcSetAlarm(10, 25, 6, 16, 6); // Set alarm 10 seconds from now
  
    attachInterrupt(39, alarmISR, FALLING); // Set interrupt function and interrupt mode
}

// Variable that keeps count on how much screen has been partially updated
int n = 0;
void loop()
{
    inkplate.clearDisplay();         // Clear frame buffer of inkplate
    inkplate.setCursor(100, 100);    // Set position of the text
    inkplate.rtcGetRtcData();          // Get the time and date from RTC

    // Print the time on screen
    printTime(inkplate.rtcGetHour(), inkplate.rtcGetMinute(), inkplate.rtcGetSecond(), inkplate.rtcGetDay(), inkplate.rtcGetWeekday(), inkplate.rtcGetMonth(), inkplate.rtcGetYear());
    
    if (_alarmFlag)     // Check alarm flag
    {
        // _alarmFlag = 0;              // Uncomment if you want to clear this flag
        inkplate.rtcClearAlarmFlag();    // It's recommended to clear alarm flag after alarm has occurred
        inkplate.setCursor(200, 200);    // Set position of the text
        inkplate.print("ALARM");         // Print text
    }
    
    if (n > 9) // Check if you need to do full refresh or you can do partial update
    {
        inkplate.display(true); // Do a full refresh
        n = 0;
    }
    else
    {
        inkplate.partialUpdate(false, true); // Do partial update and keep e-paper power supply on
        n++;                                // Keep track on how many times screen has been partially updated
    }

    delay(700);                             // Delay between refreshes.
}

void printTime(uint8_t _hour, uint8_t _minutes, uint8_t _seconds, uint8_t _day, uint8_t _weekday, uint8_t _month,
               uint16_t _year)
{
    // Write time and date info on screen
    char *wday[] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};

    print2Digits(_hour);
    inkplate.print(':');
    print2Digits(_minutes);
    inkplate.print(':');
    print2Digits(_seconds);

    inkplate.print(' ');

    inkplate.print(wday[_weekday]);
    inkplate.print(", ");
    print2Digits(_day);
    inkplate.print('/');
    print2Digits(_month);
    inkplate.print('/');
    inkplate.print(_year, DEC);
}

void print2Digits(uint8_t _d)
{
    if (_d < 10)
        inkplate.print('0');
    inkplate.print(_d, DEC);
}

Full examples​

For full working code examples, which provide a great overview, a real-world use scenario and code comments, see the links below:

Inkplate6FLICK_RTC_Alarm.ino

This example will show how to set time and date, how to set up an alarm, how to read time, how to print time on Inkplate using partial updates and how to handle interrupt.

Inkplate6FLICK_RTC_Interrupt_Alarm.ino

This example will show how to set time and date, how to set up an alarm, how to read time, how to print time on Inkplate using partial updates and how to handle interrupt.