text: /*!
      \file  main.c
      \brief TIMER2 input capture demo
  */
  
  /*
      Copyright (C) 2017 GigaDevice
  
      2014-12-26, V1.0.0, platform GD32F1x0(x=3,5)
      2016-01-15, V2.0.0, platform GD32F1x0(x=3,5,7,9)
      2016-04-30, V3.0.0, firmware update for GD32F1x0(x=3,5,7,9)
      2017-06-19, V3.1.0, firmware update for GD32F1x0(x=3,5,7,9)
  */
  
  #include "gd32f1x0.h"
  #include <stdio.h>
  #include "gd32f1x0_eval.h"
  
  void gpio_configuration(void);
  void timer_configuration(void);
  void nvic_configuration(void);
  int fputc(int ch, FILE *f);
  
  /* retarget the C library printf function to the USART */
  int fputc(int ch, FILE *f)
  {
      usart_data_transmit(EVAL_COM1, (uint8_t) ch);
      while(usart_flag_get(EVAL_COM1, USART_FLAG_TC) == RESET);
      return ch;
  }
  
  /**
      \brief      configure the GPIO ports
      \param[in]  none
      \param[out] none
      \retval     none
    */
  void gpio_configuration(void)
  {
      rcu_periph_clock_enable(RCU_GPIOB);
  
      /*configure PB4 (TIMER2 CH0) as alternate function*/
      gpio_mode_set(GPIOB, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO_PIN_4);
      gpio_output_options_set(GPIOB, GPIO_OTYPE_PP, GPIO_OSPEED_50MHZ, GPIO_PIN_4);
  
      gpio_af_set(GPIOB, GPIO_AF_1, GPIO_PIN_4);
  }
  
  /**
      \brief      configure the nested vectored interrupt controller
      \param[in]  none
      \param[out] none
      \retval     none
    */
  void nvic_configuration(void)
  {
      nvic_priority_group_set(NVIC_PRIGROUP_PRE1_SUB3);
      nvic_irq_enable(TIMER2_IRQn, 1, 1);
  }
  
  /**
      \brief      configure the TIMER peripheral
      \param[in]  none
      \param[out] none
      \retval     none
    */
  void timer_configuration(void)
  {
      /* TIMER2 configuration: input capture mode -------------------
      the external signal is connected to TIMER2 CH0 pin(PB4)
      the rising edge is used as active edge.
      the TIMER2 CH0CV is used to compute the frequency value.
      ------------------------------------------------------------ */
      timer_ic_parameter_struct timer_icinitpara;
      timer_parameter_struct timer_initpara;
  
      rcu_periph_clock_enable(RCU_TIMER2);
  
      timer_deinit(TIMER2);
  
      /* TIMER2 configuration */
      timer_initpara.prescaler         = 71;
      timer_initpara.alignedmode       = TIMER_COUNTER_EDGE;
      timer_initpara.counterdirection  = TIMER_COUNTER_UP;
      timer_initpara.period            = 65535;
      timer_initpara.clockdivision     = TIMER_CKDIV_DIV1;
      timer_initpara.repetitioncounter = 0;
      timer_init(TIMER2,&timer_initpara);
  
      /* TIMER2  configuration */
      /* TIMER2 CH0 input capture configuration */
      timer_icinitpara.icpolarity  = TIMER_IC_POLARITY_RISING;
      timer_icinitpara.icselection = TIMER_IC_SELECTION_DIRECTTI;
      timer_icinitpara.icprescaler = TIMER_IC_PSC_DIV1;
      timer_icinitpara.icfilter    = 0x0;
      timer_input_capture_config(TIMER2, TIMER_CH_0, &timer_icinitpara);
  
      /* auto-reload preload enable */
      timer_auto_reload_shadow_enable(TIMER2);
      /* clear channel 0 interrupt bit */
      timer_interrupt_flag_clear(TIMER2, TIMER_INT_CH0);
      /* channel 0 interrupt enable */
      timer_interrupt_enable(TIMER2, TIMER_INT_CH0);
  
      /* TIMER2 counter enable */
      timer_enable(TIMER2);
  }
  
  /*!
      \brief      main function
      \param[in]  none
      \param[out] none
      \retval     none
  */
  int main(void)
  {
      gpio_configuration(); 
      gd_eval_com_init(EVAL_COM1);
      nvic_configuration();
      timer_configuration();
  
      while (1);
  }
  