This is my DIY Electronic Alarm, now the prototype has been finished with breadboard,   but the PCB layout has not been finished yet.   I use a MCU(Arduino Uno) and four 74LS47 7-segment-display drivers to control   the four 7-segment-displays to show the digits of Minutes and Seconds.   When the alarm is triggered, the buzzer will generate sound.                     
    Here is the implementations of code for LED Tetris game.    #include "config.h"  #include <stdio.h>    void write_data(unsigned char,unsigned char); //Writing data to the MAX7219 chip to display different 8x8 LED patterns    unsigned int led_element[8][8];  //Global variables 2D array for static tetris blocks   unsigned int decimal_value=0;   unsigned int row_cancel=0; //stores the current number of rows cancelled   unsigned int button_pressed=0;  unsigned int step_fallen=0 ;   //unsigned int random_total;   unsigned int block_type;   unsigned char x_button=3 ; //Global variables x for the coordinates of the temp falling block                      //Declaring x corrdinate of temp falling block allows you to modify its coordinate everywhere, in any scope        unsigned int rotation_index = 0;   unsigned int rotation_button_pressed = 2;   unsigned int score=0;   unsigned int n;  unsigned int first_digit;  unsigned int ...