// pin connections
// arduino pin 2 -> kbd PIC socket 35 (data)
// arduino pin 3 -> kbd PIC socket 36 (clock)
// arduino pin 4 -> kbd PIC socket 37 (data ready/ write?)

// escape codes see https://en.wikipedia.org/wiki/ASCII#Control_characters
// \M = carriage return
// \H = backspace etc

char debugstr[100];


const int SHIFT=5;
const int CTRL =13;
const int CAPS_LOCK=A6;

const int PIN_SR_DATA=6;
const int PIN_SR_SHIFT=7;
const int PIN_SR_LATCH=8;

const int PIN_OUT_DATA=4;
const int PIN_OUT_CLOCK=3;
const int PIN_OUT_LATCH=2;

bool repeat_on=false;
int  repeat_cnt=0;
char last_c=0;

void setup() {
  // put your setup code here, to run once:

  Serial.begin(115200);
  pinMode(PIN_OUT_DATA, OUTPUT); // kbd out data
  pinMode(PIN_OUT_CLOCK, OUTPUT); // kbd out shift
  pinMode(PIN_OUT_LATCH, OUTPUT); // kbd out latch
  digitalWrite(PIN_OUT_DATA,0);
  digitalWrite(PIN_OUT_CLOCK,0);
  digitalWrite(PIN_OUT_LATCH,0);  
  
  pinMode(SHIFT, INPUT); 
  pinMode(CTRL, INPUT); 
  pinMode(CAPS_LOCK,INPUT);
  
  pinMode(PIN_SR_DATA, OUTPUT); 
  digitalWrite(PIN_SR_DATA,0);  
  pinMode(PIN_SR_SHIFT, OUTPUT); 
  digitalWrite(PIN_SR_SHIFT,0); 
  pinMode(PIN_SR_LATCH, OUTPUT); 
  digitalWrite(PIN_SR_LATCH,0);   

  pinMode(A0,INPUT);  
  pinMode(A1,INPUT);
  pinMode(A2,INPUT);
  pinMode(A3,INPUT);
  pinMode(A4,INPUT);
  pinMode(A5,INPUT);
  pinMode(A0,INPUT);
  pinMode(9,INPUT);
  pinMode(10,INPUT);
  pinMode(11,INPUT);
  pinMode(12,INPUT);  


  // bodge reset
  digitalWrite(PIN_SR_DATA,0);  

  // shift it 8 times
  for(int i=0;i<8;i++) {
    digitalWrite(PIN_SR_SHIFT,1); 
    delay(1);
    digitalWrite(PIN_SR_SHIFT,0);   
  }
}


char matrix[10][8]={

/*          0    1    2    3    4    5    6    7    8    9    10 * /
/* 0  */ { 10,   11, 'p', '=', ',', 'k', 'u', '7', },
/* 1  */ {127,   13, '`', '\\','m', 'j', 't', '5', },
/* 2  */ { '~', '~', '~', '~', 'n', 'g', 'y', '6', },
/* 3  */ { '~', '~', '~', '~', 'b', 'f', 'r', '4', },
/* 4  */ { '~', '~', '~', '~', 'v', 'h', 'e', '3', },
/* 5  */ { '~', '~', '~', '~', 'c', 's', 'w', '2', },
/* 6  */ { '~', '~', '~', '~', 'x', 'd', 'q', '1', },
/* 7  */ { '~', '~', '~', '~', 'z', 'a',  9 ,  27, },
/* 8  */ { 21, '\'', ']', '-', '/', 'l', 'o', '9', },
/* 9  */ { 8 , ' ',  '[', '0', '.', ';', 'i', '8', },
  
  };

char shifted_matrix[10][8]={

/*          0    1    2    3    4    5    6    7    8    9    10 * /
/* 0  */ { 10,   11, 'P', '+', '<', 'K', 'U', '&', },
/* 1  */ {127,   13, '~', '|', 'M', 'J', 'T', '%', },
/* 2  */ { '~', '~', '~', '~', 'N', 'G', 'Y', '^', },
/* 3  */ { '~', '~', '~', '~', 'B', 'F', 'R', '$', },
/* 4  */ { '~', '~', '~', '~', 'V', 'H', 'E', '#', },
/* 5  */ { '~', '~', '~', '~', 'C', 'S', 'W', '@', },
/* 6  */ { '~', '~', '~', '~', 'X', 'D', 'Q', '!', },
/* 7  */ { '~', '~', '~', '~', 'Z', 'A',  9 ,  27, },
/* 8  */ { 21,  '"', '}', '_', '?', 'L', 'O', '(', },
/* 9  */ { 8 , ' ',  '{', ')', '>', ':', 'I', '*', },
  
  };  

void loop() {

  short int i=-1;
  short int j=-1;
  short int down=0;
  for(short int _i=0;_i<8;_i++) {

    // write 1 data to SR on first pass only
    digitalWrite(PIN_SR_DATA,_i==0?1:0);  
    delay(1);
  
    // shift it
    digitalWrite(PIN_SR_SHIFT,1); 
    delay(1);
    digitalWrite(PIN_SR_SHIFT,0); 
  
    // latch it
    digitalWrite(PIN_SR_LATCH,1);
    delay(1);
    digitalWrite(PIN_SR_LATCH,0);
  
    // do a scan
    // sprintf(debugstr, "%d %d %d %d %d %d %d %d %d %d",  digitalRead(A0), digitalRead(A1), digitalRead(A2), digitalRead(A3), digitalRead(A4), digitalRead(A5), digitalRead(9), digitalRead(10), digitalRead(11), digitalRead(12));
    // Serial.println(debugstr);       

    // j=-1;
    for(short int _j=0; _j<10; _j++) {    
      switch(_j) {
        case 0: if(digitalRead(A0)) { i=_i; j=_j; down++; } break;
        case 1: if(digitalRead(A1)) { i=_i; j=_j; down++; } break;
        case 2: if(digitalRead(A2)) { i=_i; j=_j; down++; } break;
        case 3: if(digitalRead(A3)) { i=_i; j=_j; down++; } break;
        case 4: if(digitalRead(A4)) { i=_i; j=_j; down++; } break;
        case 5: if(digitalRead(A5)) { i=_i; j=_j; down++; } break;
        case 6: if(digitalRead(9))  { i=_i; j=_j; down++; } break;
        case 7: if(digitalRead(10)) { i=_i; j=_j; down++; } break;
        case 8: if(digitalRead(11)) { i=_i; j=_j; down++; } break;
        case 9: if(digitalRead(12)) { i=_i; j=_j; down++; } break;
      }
    }
  }

  if(j==-1) {
    repeat_on=false;
    repeat_cnt=0;
  }
  else {
    char c=matrix[j][i];
    if(c==last_c) {
      repeat_cnt++;
      if(repeat_cnt>=30) repeat_on=true;
    }
    else {
      repeat_on=false;
      repeat_cnt=1;
    }
  }
  if(j>=0 && (repeat_on || repeat_cnt==1) && down==1) {
    sprintf(debugstr, "i=%d j=%d caps=%d (analog=%d)", i, j, digitalRead(CAPS_LOCK), analogRead(CAPS_LOCK));
    Serial.println(debugstr);   
    char c=matrix[j][i];
    if(!digitalRead(SHIFT)) send_char(shifted_matrix[j][i]);   
    else if(!digitalRead(CTRL) && c>='a' && c<='z') send_char(c-'a'+1);
    else if(analogRead(CAPS_LOCK)<100 && c>='a' && c<='z') send_char(c-'a'+'A');
    else send_char(c);   
    last_c=c;
  }   
}


void send_char(char c) {

    // you don't actually need this most sig bit but sending it works, so why not
    digitalWrite(PIN_OUT_DATA,bitRead(c,7)); // bit
    digitalWrite(PIN_OUT_CLOCK,1); // clock pulse
    digitalWrite(PIN_OUT_CLOCK,0);
  
    digitalWrite(PIN_OUT_DATA,bitRead(c,6));
    digitalWrite(PIN_OUT_CLOCK,1);
    digitalWrite(PIN_OUT_CLOCK,0);
    
    digitalWrite(PIN_OUT_DATA,bitRead(c,5));
    digitalWrite(PIN_OUT_CLOCK,1);
    digitalWrite(PIN_OUT_CLOCK,0);
  
    digitalWrite(PIN_OUT_DATA,bitRead(c,4));
    digitalWrite(PIN_OUT_CLOCK,1);
    digitalWrite(PIN_OUT_CLOCK,0);
  
    digitalWrite(PIN_OUT_DATA,bitRead(c,3));
    digitalWrite(PIN_OUT_CLOCK,1);
    digitalWrite(PIN_OUT_CLOCK,0);
  
    digitalWrite(PIN_OUT_DATA,bitRead(c,2));
    digitalWrite(PIN_OUT_CLOCK,1);
    digitalWrite(PIN_OUT_CLOCK,0);
  
    digitalWrite(PIN_OUT_DATA,bitRead(c,1));
    digitalWrite(PIN_OUT_CLOCK,1);
    digitalWrite(PIN_OUT_CLOCK,0);
  
    digitalWrite(PIN_OUT_DATA,bitRead(c,0));
    digitalWrite(PIN_OUT_CLOCK,1);
    digitalWrite(PIN_OUT_CLOCK,0);
  
    digitalWrite(PIN_OUT_LATCH,1); // data ready (required)
    
  
    //sprintf(debugstr, "send=%d c=%d", cnt++, c);
    //Serial.println(debugstr);
    delay(5);
    digitalWrite(PIN_OUT_LATCH,0);
    delay(5);
}

void serialEvent()
{
   static char lastch=0;
   static bool escape=false;
   while(Serial.available()) 
   {
      char ch = Serial.read();
      Serial.write(ch);
      if(escape) {
        send_char(ch-'A'+1);
        escape=false;
      }
      else {
        if(ch=='\\') {
          escape=true;
        }
        else {
          escape=false;
          send_char(ch);
        }
      }
      lastch=ch;
   }
   //send_char(13);
}