/* 

  Example for the STM32L031 Eval Board with 128x64 OLED at PA13/PA14
  
*/

#include <stdio.h>
#include "stm32l031xx.h"
#include "delay.h"
#include "u8x8.h"

/*=======================================================================*/
/* external functions */
uint8_t u8x8_gpio_and_delay_stm32l0(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr);

/*=======================================================================*/
/* global variables */

u8x8_t u8x8;                    // u8x8 object
uint8_t u8x8_x, u8x8_y;         // current position on the screen

volatile unsigned long SysTickCount = 0;

/*=======================================================================*/

void __attribute__ ((interrupt, used)) SysTick_Handler(void)
{
  SysTickCount++;  
}



void setHSIClock()
{
  
  /* test if the current clock source is something else than HSI */
  if ((RCC->CFGR & RCC_CFGR_SWS) != RCC_CFGR_SWS_HSI) 
  {
    /* enable HSI */
    RCC->CR |= RCC_CR_HSION;    
    /* wait until HSI becomes ready */
    while ( (RCC->CR & RCC_CR_HSIRDY) == 0 )
      ;      
 
    /* enable the HSI "divide by 4" bit */
    RCC->CR |= (uint32_t)(RCC_CR_HSIDIVEN);
    /* wait until the "divide by 4" flag is enabled */
    while((RCC->CR & RCC_CR_HSIDIVF) == 0)
      ;
    
       
    /* then use the HSI clock */
    RCC->CFGR = (RCC->CFGR & (uint32_t) (~RCC_CFGR_SW)) | RCC_CFGR_SW_HSI; 
    
    /* wait until HSI clock is used */
    while ((RCC->CFGR & RCC_CFGR_SWS) != RCC_CFGR_SWS_HSI)
      ;
  }
  
  /* disable PLL */
  RCC->CR &= (uint32_t)(~RCC_CR_PLLON);
  /* wait until PLL is inactive */
  while((RCC->CR & RCC_CR_PLLRDY) != 0)
    ;

  /* set latency to 1 wait state */
  FLASH->ACR |= FLASH_ACR_LATENCY;
  
  /* At this point the HSI runs with 4 MHz */
  /* Multiply by 16 device by 2 --> 32 MHz */
  RCC->CFGR = (RCC->CFGR & (~(RCC_CFGR_PLLMUL| RCC_CFGR_PLLDIV ))) | (RCC_CFGR_PLLMUL16 | RCC_CFGR_PLLDIV2); 
  
  /* enable PLL */
  RCC->CR |= RCC_CR_PLLON; 
  
  /* wait until the PLL is ready */
  while ((RCC->CR & RCC_CR_PLLRDY) == 0)
    ;

  /* use the PLL has clock source */
  RCC->CFGR |= (uint32_t) (RCC_CFGR_SW_PLL); 
  /* wait until the PLL source is active */
  while ((RCC->CFGR & RCC_CFGR_SWS) != RCC_CFGR_SWS_PLL) 
    ;

  SystemCoreClockUpdate();				/* Update SystemCoreClock global variable */  
}

/*
  Enable several power regions: PWR, GPIOA

  This must be executed after each reset.
*/
void startUp(void)
{  
  RCC->IOPENR |= RCC_IOPENR_IOPAEN;		/* Enable clock for GPIO Port A */
  RCC->APB1ENR |= RCC_APB1ENR_PWREN;	/* enable power interface (PWR) */
  PWR->CR |= PWR_CR_DBP;				/* activate write access to RCC->CSR and RTC */  
  
  SysTick->LOAD = (SystemCoreClock/1000)*50 - 1;   /* 50ms task */
  SysTick->VAL = 0;
  SysTick->CTRL = 7;   /* enable, generate interrupt (SysTick_Handler), do not divide by 2 */      
}

/*=======================================================================*/
/* u8x8 display procedures */

void initDisplay(void)
{
  u8x8_Setup(&u8x8, u8x8_d_ssd1306_128x64_noname, u8x8_cad_ssd13xx_i2c, u8x8_byte_sw_i2c, u8x8_gpio_and_delay_stm32l0);
  u8x8_InitDisplay(&u8x8);
  u8x8_ClearDisplay(&u8x8);
  u8x8_SetPowerSave(&u8x8, 0);
  u8x8_SetFont(&u8x8, u8x8_font_amstrad_cpc_extended_r);  
  u8x8_x = 0;
  u8x8_y = 0;  
}


void outChar(uint8_t c)
{
  if ( u8x8_x >= u8x8_GetCols(&u8x8) )
  {
    u8x8_x = 0;
    u8x8_y++;
  }
  u8x8_DrawGlyph(&u8x8, u8x8_x, u8x8_y, c);
  u8x8_x++;
}

void outStr(const char *s)
{
  while( *s )
    outChar(*s++);
}

void outHexHalfByte(uint8_t b)
{
  b &= 0x0f;
  if ( b < 10 )
    outChar(b+'0');
  else
    outChar(b+'a'-10);
}

void outHex8(uint8_t b)
{
  outHexHalfByte(b >> 4);
  outHexHalfByte(b);
}

void outHex16(uint16_t v)
{
  outHex8(v>>8);
  outHex8(v);
}

void outHex32(uint32_t v)
{
  outHex16(v>>16);
  outHex16(v);
}

void setRow(uint8_t r)
{
  u8x8_x = 0;
  u8x8_y = r;
}


/*=======================================================================*/

int main()
{
  
  setHSIClock();        /* enable 32 MHz Clock */
  startUp();               /* enable systick irq and several power regions  */
  initDisplay();          /* aktivate display */
  
  setRow(0); outStr("Hello World!"); 
  setRow(2); outStr("RCC_CSR:"); outHex32(RCC->CSR); 
  setRow(3); outStr("PWR_CSR:"); outHex32(PWR->CSR); 

  for(;;)
  {
  }
}