/* demonstrate a multiplexed display controlled via the PIO8255 */

// base address for the stack. This leaves very little space for
// the stack, but means that you can watch program-code and stack
// and heap accesses at the same time in the memory editor.
// Remember that byte-address 0x800 is displayed at word-address 0x200
// in the RAM editor.
#define STACKBASE 0x00000800

// base address for some debugging output in the RAM.
// Remember that byte-address 0x880 is displayed at word-address 0x220
// in the RAM editor.
#define BASE 0x00000880 

// axxx.xxxx is mapped to 0xxx.xxxx by the (static) R-3000 MMU
// but remains axxx.xxx in this demo because we disable the MMU.
#define PIO_BASE  0xa0080000

#define PIO_REGA  (PIO_BASE+0)
#define PIO_REGB  (PIO_BASE+4)
#define PIO_REGC  (PIO_BASE+8)
#define PIO_XREG  (PIO_BASE+12)

#define PIO_MODE_CHANGE    0x80
#define PIO_GROUPA_MODE0   0x00
#define PIO_GROUPA_MODE1   0x20
#define PIO_GROUPA_MODE2   0x60
#define PIO_GROUPB_MODE0   0x00
#define PIO_GROUPB_MODE1   0x04

#define PIO_PORTA_INPUT    0x10
#define PIO_PORTA_OUTPUT   0x00
#define PIO_UPPERC_INPUT   0x08
#define PIO_UPPERC_OUTPUT  0x00
#define PIO_PORTB_INPUT    0x02
#define PIO_PORTB_OUTPUT   0x00
#define PIO_LOWERC_INPUT   0x01
#define PIO_LOWERC_OUTPUT  0x00


void pioSetMode( int value ) {
  int *xreg   = (int*) PIO_XREG;
  int command = PIO_MODE_CHANGE | (value&0x000000ff);
  *xreg = command;
}

void pioWritePortA( int value ) {
  int *reg = (int*) PIO_REGA;
  int data = value & 0x000000ff;
  *reg = data;
}

void pioWritePortB( int value ) {
  int *reg = (int*) PIO_REGB;
  int data = value & 0x000000ff;
  *reg = data;
}

void pioWritePortC( int value ) {
  int *reg = (int*) PIO_REGC;
  int data = value & 0x000000ff;
  *reg = data;
}

void pioWriteUpperC( int value ) {
  int *reg = (int*) PIO_REGC;
  int data = (*reg & 0x0000000f) | value & 0x000000f0;
  *reg = data;
}

void pioWriteLowerC( int value ) {
  int *reg = (int*) PIO_REGC;
  int data = (*reg & 0x000000f0) | value & 0x0000000f;
  *reg = data;
}

int pioReadPortA() {
  int *reg = (int*) PIO_REGA;
  int data = *reg;
  return data;
}

int pioReadPortB() {
  int *reg = (int*) PIO_REGB;
  int data = *reg;
  return data;
}

int pioReadPortC() {
  int *reg = (int*) PIO_REGC;
  int data = *reg;
  return data;
}


/*
   +-A-+
   F   B
   +-G-+
   E   C
   +-D-+ (P)

   encoding is 0000....00 PGFEDCBA

   p is not driven by this routine. If necessary,   
   OR the return value with mask 0x80.
 */
int sevenSegment( int value ) {
  switch( value ) {
    case   0: return  0x0000003f; // 00111111
    case   1: return  0x00000006; // 00000110
    case   2: return  0x0000005b; // 01011011
    case   3: return  0x0000004f; // 01001111
    case   4: return  0x00000066; // 01100110
    case   5: return  0x0000006d; // 01101101
    case   6: return  0x0000007d; // 01111101
    case   7: return  0x00000007; // 00000111
    case   8: return  0x0000007f; // 01111111
    case   9: return  0x0000006f; // 01101111

    case 0xa: return  0x00000077; // 01110111
    case 0xb: return  0x0000007c; // 01111100
    case 0xc: return  0x00000039; // 00111001
    case 0xd: return  0x0000005e; // 01011110
    case 0xe: return  0x00000079; // 01111001
    case 0xf: return  0x00000071; // 01110001

    default:  // three horizontal bars as error indicator
              return  0x00000049; // 01001001  
  }
}


void waitLoop() {
  int i, limit;
  int *ptr;
  ptr = (int*) BASE;
  limit = 0x0015;
  for( i=0; i < limit; i++ ) {
    *ptr = i; 
  }
}


void displayValue( int value ) {
  int tmp, mask, hex, segs, i;
  int ndigits = 5;

  int *ptr = (int*) BASE;
  *(ptr-1) = 0xdeadbeef;
  *(ptr-2) = value;

  mask = 0xf;
  for( i=0; i < ndigits; i++ ) {
    pioWritePortB( 0x00 ); // all digits off

    hex  = value & mask;  
    segs = sevenSegment( hex >> (i << 2) ); 

    pioWritePortA( segs );
    pioWritePortB( 1 << i ); // one digit on
    waitLoop();

    mask = mask << 4;
  }

  pioWritePortB( 0 ); // disable all digits again
}




int main( int argc, char** argv ) {
  int count;


  pioSetMode(   PIO_MODE_CHANGE 
              | PIO_GROUPA_MODE0 
              | PIO_GROUPB_MODE0 
              | PIO_PORTA_OUTPUT 
              | PIO_PORTB_OUTPUT 
              | PIO_UPPERC_INPUT 
              | PIO_LOWERC_INPUT 
            );

  for( count=0; ; count++ ) {
    displayValue( count );
  }
   
}