Keypad Demo V.3 OK

#include "stm32f10x.h"
#include "stm32f10x_tim.h"
#include "stm32f10x_rcc.h"
#include "stm32f10x_gpio.h"
#include "stm32f10x_usart.h"
#include "misc.h"
#include "stm32f10x_exti.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

USART_InitTypeDef USART_InitStruct; // this is for the USART1 initilization
GPIO_InitTypeDef  GPIO_InitStructure;

void GPIO_Config(void);
void init_USART1(uint32_t baudrate);
void USART_puts(USART_TypeDef* USARTx, volatile char *s);

char text[100] = "";
int data[100];
int i = 0;
int j = 0;
int state = 0;
uint32_t last_time = 0;
uint32_t temp_time = 0;
uint32_t temp = 0; //store data to check
int value;
int column;
int row;
// constant values
const int ROWS = 4;
const int COLS = 4;
int keys[4][4] = {{'1','2','3','A'},{'4','5','6','B'},{'7','8','9','C'},{'*','0','#','D'}};
//int keys[4][4] = {{1,2,3,3},{4,5,6,6},{7,8,9,9},{0,0,0,0}};
int input[4] = {(uint16_t)0x0001,(uint16_t)0x0002,(uint16_t)0x0004,(uint16_t)0x0008};
int rowPins[4] = {0,1,2,3};   // connect B0,1,2,3 to Rows 1-4 (the left four pins)
int colPins[4] = {0,1,2,3};   // connect A0,1,2,3 to Column 1-4 (the right four pins)
#define A_PORT GPIOA
#define B_PORT GPIOB
int key;

int main(void)
{

    GPIO_Config();
    init_USART1(9600); // initialize USART1 @ 115200 baud
   // USART_puts(USART1, "Start!\r\n"); // just send a message to indicate that it works

    GPIO_WriteBit(A_PORT,GPIO_Pin_0,Bit_SET);
    GPIO_WriteBit(A_PORT,GPIO_Pin_1,Bit_SET);
    GPIO_WriteBit(A_PORT,GPIO_Pin_2,Bit_SET);
    GPIO_WriteBit(A_PORT,GPIO_Pin_3,Bit_SET);
        GPIO_WriteBit(B_PORT,GPIO_Pin_0,Bit_SET);
        GPIO_WriteBit(B_PORT,GPIO_Pin_1,Bit_SET);
        GPIO_WriteBit(B_PORT,GPIO_Pin_2,Bit_SET);
        GPIO_WriteBit(B_PORT,GPIO_Pin_3,Bit_SET);

    USART_puts(USART1, "Start!\r\n"); // just send a message to indicate that it works
    while (1)
    {
                value = getKey();
                sprintf (text, "%c\r\n", value);
                /* delay */
            //  for(i=0;i<0x330000;i++); // is 1 second
                USART_puts(USART1, text);

    }
}

int j;
int i;
int getKey(void)
{
     int key_pressed = 0;

      for (j=0; j < ROWS; j++) { // scan the j-th row (j=0,1,2,3)
        for (i=0; i < ROWS; i++) {
          // output HIGH to all rows, except the j-th row
            if(i==j){
                 GPIO_WriteBit(B_PORT,input[i],Bit_RESET);
            }else{
                 GPIO_WriteBit(B_PORT,input[i],Bit_SET);
            }
        }
        for (i=0; i < COLS; i++) {
            if(GPIO_ReadInputDataBit(GPIOA,input[i]) == 0){ // Button at (R,C)=(j,i) is pressed
             // wait until the button is released.
             while ( GPIO_ReadInputDataBit(GPIOA,input[i]) == 0 ) ; // blocking
             key_pressed = keys[j][i]; // get the associated key for that button
             break;
          }
        }
        GPIO_WriteBit(B_PORT,input[j],Bit_SET);
        if ( key_pressed != 0 ) {
          return key_pressed;
        }
      }
      return 0; // no key pressed
    }

void GPIO_Config(void)
{
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB | RCC_APB2Periph_USART1 |
            RCC_APB2Periph_GPIOA, ENABLE);
    //OUTPUT B = ROW
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    //USART1 (PA9)
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; //USART1_TX
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    //INPUT A = COLUMN
       GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;
       GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
       GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
       GPIO_Init(GPIOA, &GPIO_InitStructure);
}

void init_USART1(uint32_t baudrate){
    USART_InitStruct.USART_BaudRate = baudrate;  // the baudrate is set to the value we passed into this init function
    USART_InitStruct.USART_WordLength = USART_WordLength_8b;  // we want the data frame size to be 8 bits (standard)
    USART_InitStruct.USART_StopBits = USART_StopBits_1;  // we want 1 stop bit (standard)
    USART_InitStruct.USART_Parity = USART_Parity_No;  // we don't want a parity bit (standard)
    USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None; // we don't want flow control (standard)
    USART_InitStruct.USART_Mode = USART_Mode_Tx;  // we want to enable the transmitter and the receiver
    USART_Init(USART1, &USART_InitStruct);  // again all the properties are passed to the USART_Init function which takes care of all the bit setting

    USART_ITConfig(USART1, USART_IT_RXNE, DISABLE);             // enable the USART1 receive interrupt
    USART_Cmd(USART1, ENABLE);
}

void USART_puts(USART_TypeDef* USARTx, volatile char *s){
    while(*s){
        // wait until data register is empty
        while( !(USARTx->SR & 0x00000040) );
        USART_SendData(USARTx, *s);
        *s++;
    }
}