I'm trying to change the pin, that is connected to TIM2 in PWM Input mode for frequency measurement.

I just compiled the example, tested it and it works on pin PB03, however, when I try to change the pin to anything else, e.g. PB4, or PA10 the pin doesn't connect to the Timer at all. (Tried through debug.)


The setup code: //The only changes are in the GPIOConf

static void TIM_Config(void)
  GPIO_InitTypeDef GPIO_InitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;
  TIM_ICInitTypeDef  TIM_ICInitStructure;  
  /* TIM2 clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

  /* GPIOB clock enable */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE); //Change here, to GPIOA 

  /* TIM2 chennel2 configuration : PB.03 */
  GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_10;  //Change here, to pin 10
  GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP ;
  GPIO_Init(GPIOA, &GPIO_InitStructure);   //Change to GPIOA

  /* Connect TIM pin to AF2 */
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_2); //And change to pin 10

  /* Enable the TIM2 global Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

   /* --------------------------------------------------------------------------- 
    TIM2 configuration: PWM Input mode
     The external signal is connected to TIM2 CH2 pin (PB.03)
     TIM2 CCR2 is used to compute the frequency value 
     TIM2 CCR1 is used to compute the duty cycle value

    In this example TIM2 input clock (TIM2CLK) is set to APB1 clock (PCLK1), since
    APB1 prescaler is set to 1.
      TIM2CLK = PCLK1 = HCLK = SystemCoreClock

    External Signal Frequency = SystemCoreClock / TIM2_CCR2 in Hz.
    External Signal DutyCycle = (TIM2_CCR1*100)/(TIM2_CCR2) in %.
  SystemCoreClock variable holds HCLK frequency and is defined in system_stm32f0xx.c file.
  Each time the core clock (HCLK) changes, user had to call SystemCoreClockUpdate()
  function to update SystemCoreClock variable value. Otherwise, any configuration
  based on this variable will be incorrect.
  --------------------------------------------------------------------------- */

  TIM_ICInitStructure.TIM_Channel = TIM_Channel_2;
  TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
  TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
  TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
  TIM_ICInitStructure.TIM_ICFilter = 0x0;

  TIM_PWMIConfig(TIM2, &TIM_ICInitStructure);

  /* Select the TIM2 Input Trigger: TI2FP2 */
  TIM_SelectInputTrigger(TIM2, TIM_TS_TI2FP2);

  /* Select the slave Mode: Reset Mode */
  TIM_SelectSlaveMode(TIM2, TIM_SlaveMode_Reset);

  /* TIM enable counter */

  /* Enable the CC2 Interrupt Request */

And the Interrupt code: //I have changed nothing in it

void TIM2_IRQHandler(void)
  /* Clear TIM2 Capture compare interrupt pending bit */
  TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);

  /* Get the Input Capture value */
  IC2Value = TIM_GetCapture2(TIM2);

  if (IC2Value != 0)
    /* Duty cycle computation */
    DutyCycle = (TIM_GetCapture1(TIM2) * 100) / IC2Value;

    /* Frequency computation */
    Frequency = SystemCoreClock / IC2Value;
    DutyCycle = 0;
    Frequency = 0;

From my understanding, everything regarding the connection to the pin should be done by the pin AF mode 2 - which should connect it to TIM2, but this apparently doesn't happen.

I'm using the STM32F072B-DISCO, and KEIL v5

It is all from the default STM32CubeFW examples, and the project can be found under STM32F072B-Discovery_FW_V1.0.1\Projects\Peripheral_Examples\TIM|PWMInput\

Thank you for any help.


This is because only specific pins of each port can have a function, in this case the Timer2_Channel2 is assignable only to PB3, and PA1 on this specific processor (STM32F072xB); see page ~43 on http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/DM00090510.pdf

Thus the pins did correctly configure as input, however they did not connect to the timer.

Its a little sad that this doesn't have static control.

  • \$\begingroup\$ as you said, you have to consult the datasheet to see which pheripherals are connected to each pin... \$\endgroup\$ – Gabriel Rezende Germanovix Nov 28 '15 at 2:23

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