#include "stm32f4xx.h"
#include "LCD2x16.c"

char Results[32768];
int ResultsPointer = 0;        

void main(void) {

  // GPIO clock enable, digital pin definitions
  RCC->AHB1ENR  |= 0x00000001;  // Enable clock for GPIOA
  RCC->AHB1ENR  |= 0x00000010;  // Enable clock for GPIOE
  GPIOE->MODER  |= 0x00010000;  // output pin PE08: time mark
  GPIOE->MODER  |= 0x00040000;  // output pin PE09: toggle
  GPIOA->MODER  |= 0x00001000;  // output pin PA06: LED D390
  GPIOA->MODER  |= 0x00004000;  // output pin PA06: LED D391
  GPIOC->MODER  |= 0x00900000;  // PC10, PC11 => AF mode
  GPIOC->AFR[0] |= 0x00000010;  // select AF1 (TIM2) for PA01 -> TIM2_CH2
  
  //UART4 initialization
  RCC->APB1ENR  |= 0x00080000;  // Enable clock for UART4
  RCC->AHB1ENR  |= 0x00000004;  // Enable clock for GPIOC
  GPIOC->MODER  |= 0x00a00000;  // PC10, PC11 => AF mode
  GPIOC->AFR[1] |= 0x00008800;  // select AF8 (UART4,5,6) for PA10, PA11 
  //UART4->BRR     = 0x1120;      // 9600 baud
  //UART4->BRR     = 0x0890;      // 19200 baud
  //UART4->BRR     = 0x0450;      // 38400 baud
  //UART4->BRR     = 0x02e0;      // 57600 baud
  UART4->BRR     = 0x016d;      // 115200 baud
  UART4->CR1    |= 0x200c;      // Enable UART for TX, RX
  UART4->CR1    |= 0x0020;      // Enable RX interrupt
  
  // ADC set-up
  RCC->APB2ENR |= 0x00000100;   //  clock for ADC1
  RCC->APB2ENR |= 0x00000200;   //  clock for ADC2
  ADC->CCR      = 0x00000006;   // Regular simultaneous mode only
  ADC1->CR2     = 0x00000001;   // ADC1 ON
  ADC1->SQR3    = 0x00000002;   // use PA02 as input
  ADC2->CR2     = 0x00000001;   // ADC1 ON
  ADC2->SQR3    = 0x00000003;   // use PA03 as input
  GPIOA->MODER |= 0x000000f0;   // PA02, PA03 are analog inputs

  ADC1->CR2    |= 0x06000000;   // use TIM2, TRG0 as SC source
  ADC1->CR2    |= 0x10000000;   // Enable external SC, rising edge
  ADC1->CR1    |= 0x00000020;   // Enable ADC Interrupt for EOC

  // NVIC IRQ enable
  NVIC_EnableIRQ(ADC_IRQn);     // Enable IRQ for ADC in NVIC 

  // Timer 2 set-up
  RCC->APB1ENR |= 0x0001;       // Enable clock for Timer 2
  TIM2->ARR     = 8400;         // Auto Reload value: 8400 == 100us
  TIM2->CR2    |= 0x0020;       // select TRGO to be update event (UE)
  //TIM2->CR1    |= 0x0001;       // Enable Counting
  
  // LCD init
  LCD_init();                   // Init LCD

  //NVIC init
  NVIC_EnableIRQ(UART4_IRQn);   // Enable IRQ for UART4 in NVIC

  // endless loop
  while (1) {
    //if (GPIOE->IDR & 0x0001) GPIOA->ODR |=  0x0040;   // LED on
    //else                     GPIOA->ODR &= ~0x0040;   // else LED off
  };
}

// IRQ function
// caution: placing breakpoints in IRQ corrupts the execution!  
// this happends due to the reading of the DR by the IAR and changes IRQ flags!
// I wasted sevaral hours to find this out. Do not step into the same trap.
void UART4_IRQHandler(void)     {  
  // TX IRQ part
  if (UART4->SR & 0x0080) {     // If TXE flag in SR is on then
    if (ResultsPointer < 32768)  // if not end of string
      UART4->DR = Results[ResultsPointer++]; // send next byte and increment pointer
    else {                      // else
      UART4->CR1 &= ~0x0080;    // disable TX interrupt
      GPIOA->ODR &= ~0x0040;
    };
  };
  // RX IRQ part
  if (UART4->SR & 0x0020) {     // if RXNE flag in SR is on then
    int RXch = UART4->DR;       // save received character & clear flag
    LCD_uInt16(RXch, 0x05, 1);  // show ASCII on LCD
    if (RXch == 'a') {
      GPIOA->ODR |=  0x0080;    // if 'a' => LED on
      ResultsPointer = 0;       // init pointer to results
      TIM2->CR1    |= 0x0001;   // Enable Counting
    };
  };
}

// IRQ function
void ADC_IRQHandler(void)       // PASS takes approx 400ns of CPU time!
{
  GPIOE->ODR |=  0x0100;        // PE08 up
  if (ResultsPointer < 32767)    {
    int Ra = ADC1->DR;
    int Rb = ADC2->DR;
    Results[ResultsPointer++] = (Ra & 0x0f00) >> 8;
    Results[ResultsPointer++] = (Ra & 0x00ff);
    Results[ResultsPointer++] = (Rb & 0x0f00) >> 8;
    Results[ResultsPointer++] = (Rb & 0x00ff);
    GPIOE->ODR |=  0x0100;
    GPIOE->ODR &= ~0x0100;
  }
  else  {
    GPIOA->ODR   &= ~0x0080;    // LED off
    TIM2->CR1    &= ~0x0001;    // Disable Counting
    UART4->CR1   |= 0x0080;     // Enable TX IRQ
    ResultsPointer = 0;
    GPIOA->ODR |=  0x0040;
    UART4->DR = Results[ResultsPointer++];   // Send first character
  };
  GPIOE->ODR &= ~0x0100;        // PE08 down
}