The HPDL-1414 is a 16-segment LED display with four printable fields that is over twenty years old. It has a red GaAsP screen to which we can add the epithet "smart", because it is capable of printing alphanumeric characters on its fields. 

The screen is controlled by a CMOS integrated circuit embedded in a plastic housing.This circuit contains RAM, ASCI II decoder, multiplexer and LED drivers. Thanks to these features, no additional components are needed to connect this display to the microcontroller. More displays can be connected in series, where for each subsequent one it is necessary to assign another GPIO to the WR pin, similar to the SPI interface.
   In one of my previous videos I presented you a miniature clock with these displays, as well as the way in which static and moving text can be written on it. Unfortunately at that moment I didn't manage to create a version of the code in which I could adjust the time manually with buttons, which would make this nice retro clock complete, although when making the case I incorporated three buttons for this purpose.

This time I will present you the new version of this project, where in addition to manually setting the time, I also added a Alarm function with a pulsating beep on a small Buzzer.
  The device is very simple to make and consists of several components:
   - Arduino nano microcontroller
   - 2 pcs. HPDL-1414 Led displays
   - DS3231 Realtime clock module
   - Three Buttons,
   - And small active Buzzer

This project is sponsored by PCBWay. This year, PCBWayorganizes the Seventh Project Design Contest where, in addition to Electronic and Mechanical Project,  also has been added a new category: STM32 Project. For the best selected projects are provided rich prizes in cash, coupons and special gifts. Submit your project for participation in this Contest from 2nd, Sep, 2024 to 19th, Jan, 2025. For more details and instructions visit the given page). Let PCBwayalways be your first choice.

 Now follows a brief description of the device's functions. Immediately after switching on, a moving demo text appears on the display, after which the set time is displayed in the form of Hours, Minutes, and Seconds. To enter the menu for setting the correct time, press the "S" button. 

Now with the "H" button the hour is set, and with the "M" button the minutes are set. With the next click on the "S" button, we enter the menu for setting the alarm. 

The setting principle is the same as before, only this time the letter "A" appears at the beginning, unlike the previous menu.
 The alarm is activated at the set time in the form of short beeps with a duration of 500mS, and is deactivated simply by pressing the set button.
  And finally a short conclusion. This is a small, simple, but really interesting unusual clock that shows the time on retro displays made by Hewlett-Packard at the turn of the last century, and was also used for calculators and measuring instruments.

#include <HPDL1414.h>
#include <RTClib.h>
#include <Wire.h>

const byte dataPins[7] = {2, 3, 4, 5, 6, 7, 8};  // Segment data pins: D0 - D6
const byte addrPins[2] = {A1, A2};               // Segment address pins: A0, A1
const byte wrenPins[] = {A0, A3};                // Write Enable pins (left to right)

RTC_DS3231 rtc;
char msg[] = "         *** MICRO CLOCK - MIRCEMK ***        ";
char t[32];
HPDL1414 hpdl(dataPins, addrPins, wrenPins, sizeof(wrenPins));

// Button pins
const int buttonHourPin = 9;
const int buttonMinutePin = 10;
const int buttonSetPin = 11;

// Buzzer pin
const int buzzerPin = 12;  // Add a pin for the buzzer

// Variables for setting time and alarm manually
int hours = 0;
int minutes = 0;
int alarmHours = 0;
int alarmMinutes = 0;
bool setMode = false;      // Time setting mode flag
bool alarmMode = false;    // Alarm setting mode flag
bool alarmEnabled = false; // Alarm enabled flag
bool alarmActive = false;  // Alarm active (sounding) flag
bool alarmAcknowledged = false...