I want to count the pulses generated by Picoscope, my signal frequency is (20Hz)

I used the timer2, the problem is that the counter increment to 1 and came back to 0, I don't understand why ??? since it must increment every 50ms.

enter image description here

I devellopped the code show bellow :

 #include "stm32f4xx.h"
 #include "stm32f4xx_rcc.h"
 #include "stm32f4xx_gpio.h"
 #include "stm32f4xx_tim.h"

 void GPIO_Init_TM(void);

 int variable = 0;

 int main(void)
    variable = TIM_GetCounter(TIM2);

 void GPIO_Init_TM(void)



RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

GPIO_InitTypeDef gpioStructure;
//TIM_TimeBaseInitTypeDef timerInitStructure;

gpioStructure.GPIO_Pin = GPIO_Pin_15 ;
gpioStructure.GPIO_Mode = GPIO_Mode_AF;
gpioStructure.GPIO_PuPd = GPIO_PuPd_UP;

GPIO_Init(GPIOA, &gpioStructure);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource15, GPIO_AF_TIM2);

TIM_EncoderInterfaceConfig(TIM2, TIM_EncoderMode_TI1,TIM_ICPolarity_Rising, TIM_ICPolarity_Rising );
TIM_SetAutoreload (TIM2, 0xffff);



and this is the result I get :

enter image description here

  • 1
    \$\begingroup\$ Any questions here? \$\endgroup\$
    – Batuu
    Jul 18, 2017 at 8:56
  • \$\begingroup\$ The counter must increment every 50ms since the Frequency is at 50 20Hz, but it increments just to 1 and came back to 0, I don't understand why ? \$\endgroup\$ Jul 18, 2017 at 9:01

1 Answer 1


Your problem is, that you configured your TIM in encoder mode. An quatrature encoder uses two inputs with 90° phase shifted pulse signals to detect up or down counting. See the red path in the picture below.

So delete :

TIM_EncoderInterfaceConfig(TIM2, TIM_EncoderMode_TI1,TIM_ICPolarity_Rising, TIM_ICPolarity_Rising );

enter image description here

If you just want a single input pulse counter, you have to use the external trigger (TIMx_ETR) as timer trigger. (green path in the pic)

Add a complete timer initialization and something like:

TIM_SelectInputTrigger(TIM2, TIM_TS_ETRF);
  • \$\begingroup\$ For Timer 9 I used this function TIM_TIxExternalClockConfig(TIM9, TIM_TIxExternalCLK1Source_TI2, TIM_ICPolarity_Rising, 0x0F); and it works, the external signal is on the pin PA3 channel 2 for the TImer 9 \$\endgroup\$ Jul 21, 2017 at 11:56

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