// ChibiMo Firmware
// Version 0.20110212
//
// (c)k.k.  q61.org  2011.
// All rights reserved.
// This firmware is provided AS-IS.  No warranty.


// pin assignment
// 13 -> PB5 -> /RESET
// 12 -> PB4 -> CS2
// 11 -> PB3 -> CS1
// 10 -> PB2 -> (NC)
//  9 -> PB1 -> DB7
//  8 -> PB0 -> DB6
//  7 -> PD7 -> DB5
//  6 -> PD6 -> DB4
//  5 -> PD5 -> DB3
//  4 -> PD4 -> DB2
//  3 -> PD3 -> DB1
//  2 -> PD2 -> DB0
//  1 -> PD1 -> (USART TxD)
//  0 -> PD0 <- (USART RxD)
// A5 -> PC5 -> E
// A4 -> PC4 -> RW
// A3 -> PC3 -> RS
// A2 -> PC2 -> (NC)
// A1 -> PC1 -> (NC)
// A0 -> PC0 -> (NC)

#define LCD_RESET_VAL  0x20
#define LCD_CS2_VAL    0x10
#define LCD_CS1_VAL    0x08
#define LCD_E_VAL      0x20
#define LCD_RS_VAL     0x08

static uint8_t  g_cs;


void lcd_write(byte val, byte dt)
{
  uint8_t valpc;
  valpc = (dt) ?  LCD_RS_VAL : 0;

  PORTC = valpc;  
  PORTB = LCD_RESET_VAL | g_cs | (val >> 6);
  PORTD = (val << 2);
  PORTC |= LCD_E_VAL;
  delayMicroseconds(1);
  PORTC = valpc;
}


void lcd_init()
{
  g_cs = (LCD_CS1_VAL | LCD_CS2_VAL);
  delay(500);
  
  lcd_write(0x3e, 0);
  delay(500);
  
  lcd_write(0x3f, 0);
  delay(100);
  lcd_write(0xc0, 0);
  delay(10);
  lcd_write(0xb8, 0);
  delay(10);
  lcd_write(0x40, 0);
  delay(10);
}


void serial_init(long baud)
{
  uint16_t  baud_setting;
  
  UCSR0A = 0;
  baud_setting = (F_CPU / 8 / baud - 1) / 2;
  UBRR0H = baud_setting >> 8;
  UBRR0L = baud_setting;

  UCSR0B = 1 << RXEN0;
}

volatile uint8_t serial_data_ready()
{
  return ((UCSR0A & (1 << RXC0)) >> RXC0);
}

volatile uint8_t serial_data_read()
{
  return (UDR0);
}

  
void setup()
{
  DDRB = 0x3f;
  DDRC = 0x3f;
  DDRD = 0xfc;
  
  lcd_init();
  
  g_cs = 0;
  
  
  serial_init(500000);
  
  g_cs = (LCD_CS1_VAL | LCD_CS2_VAL);
  for (uint8_t i = 0; i < 64; i++) {
    lcd_write(i, 1);
    delayMicroseconds(5);
  }
}

void loop()
{
  static uint8_t x = 0;
  static uint8_t y = 0;
  static uint8_t ph = 0;
  static uint8_t pxdt[10];
  uint8_t  dt;
  
  while (!serial_data_ready()) {
    ;
  }
  
  {
    dt = serial_data_read();
    
    switch (ph++) {
    case 0:
      if (dt & 0x80) {
        ph = 0; // invalid address, reset state
      } else {
        y = dt >> 4;
        g_cs = LCD_CS1_VAL + (dt & 0x08);
        lcd_write(0xb8 | y, 0);
        x = (dt & 0x07) << 3;
      }
      break;
    case 1: 
      delayMicroseconds(5);
      lcd_write(0x40 | x, 0);
      pxdt[ph] = dt;
      break;
    case 2: case 3: case 4: case 5: case 6: case 7:
      lcd_write(pxdt[ph - 1], 1);
      pxdt[ph] = dt;
      break;
    case 8:
      lcd_write(pxdt[ph - 1], 1);
      delayMicroseconds(5);
      lcd_write(dt, 1);
      ph = 0;
      break;
    default:
      ph = 0;
      break;
    }
  }
}