/*
 *  startup.c
 *
 */
#include <stdio.h>

void startup(void) __attribute__((naked)) __attribute__((section (".start_section")) );

void startup ( void )
{
__asm volatile(
    " LDR R0,=0x2001C000\n"     /* set stack */
    " MOV SP,R0\n"
    " BL main\n"                /* call main */
    "_exit: B .\n"              /* never return */
    ) ;
}

typedef struct {
  uint32_t moder;
  uint16_t otyper;      // +0x4
  uint16_t otReserved;
  uint32_t ospeedr;     // +0x8
  uint32_t pupdr;       // +0xc
  uint8_t  idrLow;      // +0x10
  uint8_t  idrHigh;     // +0x11
  uint16_t idrReserved;
  uint8_t  odrLow;      // +0x14
  uint8_t  odrHigh;     // +0x15
  uint16_t odrReserved;
} GPIO;

typedef struct {
  uint32_t ctrl;
  uint32_t load;
  uint32_t val;
  uint32_t calib;
} SysTick;

#define GPIO_E (*((volatile GPIO*) 0x40021000))
#define SYSTICK (*((volatile SysTick*) 0xE000E010))

#define CLOCK_FREQ 168000000

#define B_E      0x40 // 0100 0000
#define B_SELECT 0x04 // 0000 0100
#define B_RW     0x02 // 0000 0010
#define B_RS     0x01 // 0000 0001

void delay_250ns(void)
{
  SYSTICK.ctrl = 0;
  SYSTICK.load = (CLOCK_FREQ * 0.00000025) - 1;
  SYSTICK.val = 0;
  SYSTICK.ctrl = 5;

  while ((SYSTICK.ctrl & 0x00010000) == 0) {};

  SYSTICK.ctrl = 0;
}

void delay_micro(unsigned int us)
{
  while (us--) {
    delay_250ns();
    delay_250ns();
    delay_250ns();
    delay_250ns();
  }
}

void delay_milli(unsigned int ms)
{
#ifdef SIMULATOR
  ms = ms / 1000;
  ms++;
#endif

  while (ms--) {
    delay_micro(1000);
  }
}



void ascii_write_controller(uint8_t c)
{
  ascii_ctrl_bit_set(B_E);
  GPIO_E.odrHigh = c;

  delay_250ns();

  ascii_ctrl_bit_clear(B_E);
}

void ascii_write_cmd(uint8_t cmd)
{
  ascii_ctrl_bit_clear(B_RS);
  ascii_ctrl_bit_clear(B_RW);

  ascii_write_controller(cmd);
}

void ascii_write_data(uint8_t data)
{
  ascii_ctrl_bit_set(B_RS);
  ascii_ctrl_bit_clear(B_RW);

  ascii_write_controller(data);
}


uint8_t ascii_read_controller(void)
{
  ascii_ctrl_bit_set(B_E);

  delay_250ns();
  delay_250ns();

  uint8_t rv = GPIO_E.idrHigh;

  ascii_ctrl_bit_clear(B_E);

  return rv;
}

uint8_t ascii_read_status(void)
{
  GPIO_E.moder &= 0xFFFF00FF; // 0000 0000 0000 0000 FFFF FFFF FFFF FFFF

  ascii_ctrl_bit_clear(B_RS);
  ascii_ctrl_bit_set(B_RW);

  uint8_t rv = ascii_read_controller();

  GPIO_E.moder |= 0x00005500; // 0101 0101 0101 0101 0000 0000 0000 0000

  return rv;
}

uint8_t ascii_read_data(void)
{
  GPIO_E.moder &= 0xFFFF00FF; // 0000 0000 0000 0000 FFFF FFFF FFFF FFFF

  ascii_ctrl_bit_set(B_RS);
  ascii_ctrl_bit_set(B_RW);

  uint8_t rv = ascii_read_controller();

  GPIO_E.moder |= 0x00005500; // 0101 0101 0101 0101 0000 0000 0000 0000

  return rv;
}


void ascii_ctrl_bit_set(uint8_t b)
{
  GPIO_E.odrLow |= B_SELECT | b;
}

void ascii_ctrl_bit_clear(uint8_t b)
{
  GPIO_E.odrLow &= B_SELECT | ~b;
}

void ascii_wait_ready()
{
  while ((ascii_read_status() & 0x80) == 0x80) {}
}

void ascii_command(uint8_t cmd)
{
  ascii_wait_ready();

  delay_micro(8);

  ascii_write_cmd(cmd);

#ifndef SIMULATOR
  delay_milli(2);
#endif
}

void ascii_gotoxy(uint8_t x, uint8_t y)
{
  uint8_t address;

  if (y != 1)
    address = 0x40 | (x - 1);
  else
    address = x - 1;

  ascii_write_cmd(0x80 | address);
  delay_micro(45);
}

void ascii_write_char(uint8_t c) {
  ascii_wait_ready();

  delay_micro(8);
  ascii_write_data(c);
  delay_micro(43);
}

void app_init(void)
{
  GPIO_E.moder = 0x55555555; // 0101 0101 0101 0101 0101 0101 0101 0101
}

void ascii_init(void)
{
  ascii_command(0x38);
  ascii_command(0x0C);
  ascii_command(0x01);
  ascii_command(0x06);
}

void main(void)
{
  char *s;
  char test1[] = "Alfanumerisk ";
  char test2[] = "Display - test";

  app_init();
  ascii_init();

  ascii_gotoxy(1, 1);
  s = test1;

  while (*s) {
    ascii_write_char(*s++);
  }

  ascii_gotoxy(1, 2);
  s = test2;

  while (*s) {
    ascii_write_char(*s++);
  }

  return 0;
}