// CONFIG
#pragma config FOSC = HS        // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = ON       // Power-up Timer Enable bit (PWRT enabled)
#pragma config BOREN = OFF      // Brown-out Reset Enable bit (BOR disabled)
#pragma config LVP = OFF        // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

#include <xc.h>

#define _XTAL_FREQ 20000000 // 20MHz

#define CLK PORTAbits.RA0
#define DAT PORTAbits.RA1

#define WAIT 20
#define BUFFER_SIZE 32
#define BREAK 0xF0 // Breakコード
#define ONC 16 // ON/Cキーコード

#define WAIT_HIGH while(CLK == 0);
#define WAIT_LOW while(CLK == 1);

void putKeycode(unsigned char);
unsigned char getKeycode(void);
void sendKeycode(void);

unsigned char OP[5] = {0b11110100, 0b11101100, 0b11011100, 0b10111100, 0b01111100};
unsigned char buffer[BUFFER_SIZE];
unsigned char head, tail;
int dataFlag;

const unsigned char keyMap[5][5] = {
  { 1, 18,  2,  3,  0},
  { 4, 14,  5,  6, 21},
  {23, 20, 10, 11, 15},
  {22, 99, 17, 13, 19},
  { 8, 99,  9, 12,  7}
};

unsigned char keyStat[5][5];
unsigned char keyStatExt; // "ON/C"
unsigned char keyin;
static int count = 0;

void main(void)
{
    ADCON0 = 0b00000000; // ADコンバータOFF
    ADCON1 = 0b00000110; // 全てデジタル RA2 RA3 Vref使わない
    CMCON  = 0b00000111; // コンパレータOFF
    CCP1CON = 0b00000000; // CCP1オフ 設定しなくても問題ないかも
    CCP2CON = 0b00000000; // CCP2オフ 動作に関係ないけど念の為
    TRISA  = 0b00000001;
    TRISB  = 0b00011111;
    TRISC  = 0b11111100;
    PORTA  = 0b00000000;
    PORTB  = 0b00011111;
    PORTC  = 0b00000000;
    OPTION_REGbits.nRBPU = 0; // PORTBを内部プルアップ

    //キー状態初期化
    for(int i=0; i<5; i++)
      for(int j=0; j<5; j++)
        keyStat[i][j] = 1;
    keyStatExt = 1;
    
    head = 0;
    tail = 0;
    dataFlag = 0;
    
    __delay_ms(300);
    
    while(1)
    {
        if(CLK)
            sendKeycode();
        
        for(int i=0; i<5; i++)
        {
            TRISC = OP[i];
            __delay_ms(1); // 回路の安定を待つ
            for(int j=0; j<5; j++)
            {
                keyin = PORTB;
                keyin = (keyin >> j) & 1;
                if(keyin != keyStat[i][j])
                {
                    if(keyin)
                    {
                        putKeycode(BREAK);
                        putKeycode(keyMap[i][j]);
                    }
                    else
                        putKeycode(keyMap[i][j]);

                    keyStat[i][j] = keyin;
                }
            }
        }
        
        TRISC = 0b11111000;
        __delay_ms(1); // 回路の安定を待つ
        keyin = PORTB;
        keyin = (keyin >> 3) & 1;
        if(keyin != keyStatExt)
        {
            if(keyin)
            {
                putKeycode(BREAK);
                putKeycode(ONC);
            }
            else
                putKeycode(ONC);

            keyStatExt = keyin;
        }
    }
}

// バッファにキーコードを入れる
void putKeycode(unsigned char code)
{
    unsigned char p;
    
    p = tail;
    buffer[p++] = code;
    if(p == BUFFER_SIZE)
        p = 0;
    if(p != head)
        tail = p;
    dataFlag = 1;
}

// バッファからキーコードを取り出す
unsigned char getKeycode()
{
    unsigned char val;
    
    val = buffer[head++];
    if(head == BUFFER_SIZE)
        head = 0;

    if(head == tail)
        dataFlag = 0;

    return val;
}

void sendKeycode()
{
    unsigned char code;
    
    if(dataFlag)
        code = getKeycode();
    else
        code = 0xFF;
    
    WAIT_LOW
    for(int i= 0; i<8; i++)
    {
        WAIT_HIGH
        DAT = (code >> i) & 1;
        WAIT_LOW
    }
}