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Generating a simple square signal

Question asked by naeschd on Aug 31, 2012
Latest reply on Aug 31, 2012 by naeschd
Hi at all,

I am using the STM32F4
i am trying to generate a simple square signal without using an interrupt (about 2MHz). Therfore i tried using Timer 3 in OC-Toggle mode.
See below my initialisation for Timer 3:
GPIO_InitTypeDef GPIO_InitStructure;
  TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
  TIM_OCInitTypeDef TIM_OCInitStructure;
 
  // Enable Pin
  // TIM3 clock enable
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
 
 
  // GPIOB Configuration:  TIM3 CH2 (PB5)
  GPIO_InitStructure.GPIO_Pin = TLC_GSCLK_PIN;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(TLC_PORT, &GPIO_InitStructure);
 
  // Connect TIM3 pins to AF2
  GPIO_PinAFConfig(TLC_PORT, TLC_GSCLK_PIN, GPIO_AF_TIM3);
 
  //  PrescalerValue = (uint16_t) ((SystemCoreClock /2) / 28000000) - 1;
  /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Period = 1;
  TIM_TimeBaseStructure.TIM_Prescaler = 0; //No prescaler
  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV2;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
 
  /* PWM1 Mode configuration: Channel2 */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 1;
  TIM_OC2Init(TIM3, &TIM_OCInitStructure);
  TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);
 
  TIM_ARRPreloadConfig(TIM3, ENABLE);
  /* TIM3 enable counter */
  TIM_Cmd(TIM3, ENABLE);
  TIM3->CCR2 = 1;
 When I debug my code I can see the counter is actually running. But on TLC_Port (which is Port B) TLC_GSCLK_PIN (which is Pin 5) nothing happens. Did I forget something? Did I do something wrong with the alternate function mapping?
It would be great if you could help me with that issue...
Thanks in advance.
Mathias

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