Digital alarm clock using PIC16F877 microcontroller

This is an alarm clock I built. It was very effective during the sort time I used it, because I programmed it to play a very annoying tune through a speaker. I actually started to wake up before the alarm went of, so other people in the house didn’t wake up from the annoying pitches it played.

Digital alarm clock

The JAL source code is available on my download page


  • Timekeeping using the PIC’s timer0 interrupt
  • 4×20 hd44780 compatible backlit LCD, displaying the time in big numbers (4×4 and 4×3) * Alarm sound tune using PWM
  • computer interface for synchronizing time with the web.
  • (maybe battery backup (in case of a power outage…))


Timekeeping: Rewritten in assembler. (losing one stack level, previously losing two stack levels, ISR and procedure time…) :Display: Done. Use’s Vasile’s 4-line lcd routines and tables to store the texts.
Bignumbers: Done. Data stored in tables.
Backlight: The backlight is dimmed using the internal CCP1 module of the PIC in PWM mode. :Input: Four pushbuttons on port D, handled by buttons.jal (function keypress(byte in key) return bit).
Alarm sound: Uses CCP2 in PWM mode, inspired by Vasile!
Menu code: Works. Can set time/alarm.
Computer link: (interface code) Nothing yet.

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About The Author

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.

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