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Timer enable and disable

Question asked by stone.jorge on Sep 15, 2015
Latest reply on Sep 15, 2015 by Clive One
Hi,

I have a stm32f4-disco, and I wanted to enable and disable a timer using external interrupt.
When the external signal arrives I enable the timer, and when 400 ticks have passed I disable the timer.

I thought that it would make the timer work when every interrupt arrives and stop after 400 ticks, but it only works one time.

Here's the code:
// Assumptions per system_stm32f4xx.c CPU @ 168 MHz, APB2 @ 84 MHz (/2), APB1 @ 42 MHz (/4)
 
// TIM13 40KHz PWM (PA.06 TIM13_CH1)
 
#include "stm32f4xx.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4_discovery.h"
#include "stm32f4xx_tim.h"
#include "misc.h"
#include "stm32f4xx_exti.h"
#include "stm32f4xx_syscfg.h"
 
void ClockSetUp(void) {
//  Initialize system
    SystemInit();
    RCC_DeInit();
//  PLL Setup
    RCC_HSEConfig(RCC_HSE_ON);
    RCC_WaitForHSEStartUp();
    RCC_PLLConfig(RCC_PLLSource_HSE,5,210,2,4);
    RCC_PLLCmd(ENABLE);
    while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) != SET);
    RCC_HCLKConfig(RCC_SYSCLK_Div1);
    RCC_PCLK1Config(RCC_HCLK_Div4);
    RCC_PCLK2Config(RCC_HCLK_Div2);
    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
}
 
/**************************************************************************/
 
void RCC_Configuration(void)
{
  /* GPIO's clock enable */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
 
  /* Enable SYSCFG clock */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);
 
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
 
 
  /* TIM's clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM13, ENABLE);
 
}
 
/**************************************************************************/
 
void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;
 
  /* GPIOA Configuration: TIM13 CH1 (PA6) */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
 
  /* Connect TIM13 pins to AF */
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_TIM13);
 
  /* Configure PA0 pin as input floating (EXTI, interrupcio arduino)*/
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
}
 
/**************************************************************************/
 
void NVIC_Configuration(void)
{
  NVIC_InitTypeDef NVIC_InitStructure;
 
  /* Enable the TIM13 global Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM8_UP_TIM13_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
 
}
 
/**************************************************************************/
 
uint32_t Period;
 
void TIM13_Configuration(void)
{
  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
  TIM_OCInitTypeDef  TIM_OCInitStructure;
 
  //Periode en ticks, (168Mhz/2)/40kHz
 
  Period = (SystemCoreClock / 2) / 40000; // 40 KHz, from APB1 clock *2, nominally 84 MHz
 
  /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Prescaler = 0;
  TIM_TimeBaseStructure.TIM_Period = Period - 1;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM13, &TIM_TimeBaseStructure);
 
  /* PWM1 Mode configuration: Channel1 */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse =  Period / 2; // 50/50 duty
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
 
  TIM_OC1Init(TIM13, &TIM_OCInitStructure);
  TIM_OC1PreloadConfig(TIM13, TIM_OCPreload_Enable);
 
  /* TIM Interrupts enable */
  TIM_ITConfig(TIM13, TIM_IT_Update, ENABLE);
 
}
 
/**************************************************************************/
#define TimerON 400
 
void TIM8_UP_TIM13_IRQHandler(void) // 40KHz
{
  static int modulatingcount = 0;
 
 
  // 1 Sec On - 40000 ticks// 10ms - 400 ticks
 
  if (TIM_GetITStatus(TIM13, TIM_IT_Update) != RESET) // Validate source
  {
    TIM_ClearITPendingBit(TIM13, TIM_IT_Update); // Clear source
 
    modulatingcount++;
 
    if (modulatingcount > TimerON){
        TIM_Cmd(TIM13, DISABLE);
        }
  }
}
 
/**************************************************************************************/
 
static void EXTILine0_Config(void);
void GPIO_Initialize(void);
 
 
GPIO_InitTypeDef GPIO_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
 
 
static void EXTILine0_Config(void)
{
 
 EXTI_InitTypeDef EXTI_InitStructure;
/* Connect EXTI Line0 to PA0 pin */
 SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOA, EXTI_PinSource0);
 
/* Configure EXTI Line0 */
 EXTI_InitStructure.EXTI_Line = EXTI_Line0;
 EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
 EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
 EXTI_InitStructure.EXTI_LineCmd = ENABLE;
 EXTI_Init(&EXTI_InitStructure);
 
/* Enable and set EXTI Line0 Interrupt to the lowest priority */
 NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQn;
 NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x0F;
 NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
 NVIC_Init(&NVIC_InitStructure);
}
 
void EXTI0_IRQHandler(void)
{
 if(EXTI_GetITStatus(EXTI_Line0) != RESET)
 {
     STM_EVAL_LEDToggle(LED4);
 
     TIM_Cmd(TIM13, ENABLE);
 
 /* Clear the EXTI line 0 pending bit */
 EXTI_ClearITPendingBit(EXTI_Line0);
 }
}
 
/**************************************************************************************/
 
int main(void)
{
  ClockSetUp();
 
  RCC_Configuration();
 
  NVIC_Configuration();
 
  GPIO_Configuration();
 
  TIM13_Configuration();
 
  EXTILine0_Config();
 
  STM_EVAL_LEDInit(LED4);
 
while(1){
    }
}

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