#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/timer.h>

#include <libopencm3/cm3/nvic.h>
#include <libopencm3/stm32/exti.h>

#include <libopencm3/cm3/cortex.h>

//#include <stm32f2xx_rcc.h>

static void gpio_setup ( void ) {

  /* Enable GPIOC clock. */
  rcc_peripheral_enable_clock ( &RCC_AHB1ENR, RCC_AHB1ENR_IOPCEN );

  /* Set GPIO3 to 'output push-pull'. */
  gpio_mode_setup ( GPIOC, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO3 );

}

static void nvic_setup(void) {
  /* Without this the timer interrupt routine will never be called. */
  nvic_enable_irq(NVIC_TIM2_IRQ);
  //nvic_set_priority(NVIC_TIM2_IRQ, 1);
}

static void timer2_setup ( void ) {

  /* Set timer start value. */
  TIM_CNT(TIM2) = 1;

  /* Set timer prescaler. 72MHz/1440 => 50000 counts per second. */
  TIM_PSC(TIM2) = 20000; // 120M/2000 = 60k/second

  /* End timer value. If this is reached an interrupt is generated. */
  TIM_ARR(TIM2) = 600;

  /* Update interrupt enable. */
  TIM_DIER(TIM2) |= TIM_DIER_UIE;

  //timer_set_repetition_counter ( TIM2, 100 );

  /* Start timer. */
  TIM_CR1(TIM2) |= TIM_CR1_CEN;

  return;
}

void tim2_isr ( void ) {

  //TIM2_SR &= ~TIM_SR_UIF;    //clearing update interrupt flag
  TIM_SR(TIM2) &= ~TIM_SR_UIF; /* Clear interrrupt flag. */

  __asm__("nop");

  gpio_toggle(GPIOC, GPIO3); /* LED on/off. */

}


int main ( void ) {

#if 1 // go for 120MHz, built into libopencm3
  // requires: external 8MHz crystal on pin5/6 with associated caps to ground
  rcc_clock_setup_hse_3v3 ( &hse_8mhz_3v3 [ CLOCK_3V3_120MHZ ] );
#endif

  gpio_setup();
  gpio_set ( GPIOC, GPIO3 );

  /* Enable TIM2 clock. */
  rcc_peripheral_enable_clock(&RCC_APB1ENR, RCC_APB1ENR_TIM2EN);

  //__enable_irq();
  //cm_enable_interrupts();

  nvic_setup();

  timer2_setup();

  TIM_SR(TIM2) &= ~TIM_SR_UIF; /* Clear interrrupt flag. */

  while ( 1 ) {
    __asm__("nop");
  } // while forever

  return 0;
}