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

int Table[4096], TablePtr, Am = 255, K = 655;

int main ()  {
  
  // Table init
  for (TablePtr = 0; TablePtr <= 4095; TablePtr++)
    Table[TablePtr] = (int)(1850.0 * sin((float)TablePtr / 2048.0 * 3.141592653));
  
  // 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
  
  // LCD init
  LCD_init(); LCD_string("Tp=", 0x01); LCD_string("Am=", 0x41);
  
  // DAC set-up
  RCC->APB1ENR |= 0x20000000;   // Enable clock for DAC
  DAC->CR      |= 0x00010001;   // DAC control reg, both channels ON
  GPIOA->MODER |= 0x00000f00;   // PA04, PA05 are analog outputs

  // Timer 2 set-up
  RCC->APB1ENR |= 0x0001;       // Enable clock for Timer 2
  TIM2->ARR     = 840;          // Auto Reload: 8400 == 100us -> 100kHz
  TIM2->DIER   |= 0x0001;       // DMA/IRQ Enable Register - enable IRQ on update
  TIM2->CR1    |= 0x0001;       // Enable Counting

  // NVIC IRQ enable
  NVIC_EnableIRQ(TIM2_IRQn);     // Enable IRQ for TIM2 in NVIC 

  // waste time - check pushbuttons and display parameters
  while (1) {
    if (GPIOE->IDR & 0x0001) GPIOA->ODR |=  0x0040;   // LED on
    else                     GPIOA->ODR &= ~0x0040;   // else LED off
    if ((GPIOE->IDR & 0x0004) && (K  < 32767))  K  += 1; // S372
    if ((GPIOE->IDR & 0x0008) && (K  > 2))      K  -= 1; // S373
    if ((GPIOE->IDR & 0x0010) && (Am < 255))    Am += 1; // S374
    if ((GPIOE->IDR & 0x0020) && (Am > 1))      Am -= 1; // S375
    GPIOE->ODR   |=  0x0200;    // time mark: PE09 up
    GPIOE->ODR   &= ~0x0200;    // time mark: PE09 down
    float Fp = 1e5 * K / 65536.9;  // calculate frequency
    LCD_uInt16((int)Fp,0x08,1); // display frequency
    LCD_uInt16(Am,0x48,1);      // display amplitude
  };
}

// IRQ function
void TIM2_IRQHandler(void)       // DDS takes approx 500ns of CPU time!
{
  GPIOE->ODR |=  0x0100;        // PE08 up
  TIM2->SR &= ~0x00000001;      // clear update event flag in TIM2
  TablePtr = (TablePtr + K) & 0xffff;   // increment and limit to 16 bits
  DAC->DHR12R1 = (Am * Table[  TablePtr >> 4                ]) / 256 + 2048; // Table[TablePtr] -> DAC
  DAC->DHR12R2 = (Am * Table[((TablePtr >> 4) + 1024) & 4095]) / 256 + 2048; // Table[TablePtr] -> DAC
  GPIOE->ODR &= ~0x0100;        // PE08 down
}