How to set general purpose timer to counter mode on STM32F411E? - stm32f4discovery

Question

I need a timer to increment with rising edge on the GPIO pin. I can't find any code example doing just that.
I have a digital Hall sensor which sense a magnet approaching the sensor and I want to count how many times the magnet came around the sensor. The sensor gives positive pulse when magnet goes around. I want to use this pulse to increment counter value.
I know how to set the timer into basic up-counting mode (with internal clock).
TIM_TimeBaseInitTypeDef TIM_BaseStruct;
/* Configure TIMER4*/
TIM_BaseStruct.TIM_Prescaler = 40000;
TIM_BaseStruct.TIM_CounterMode = TIM_CounterMode_Up;
TIM_BaseStruct.TIM_Period = 500;
TIM_BaseStruct.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_BaseStruct.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM4, &TIM_BaseStruct);
TIM_Cmd(TIM4, ENABLE);
And this works, but I need to switch the clock to external signal. How do I do that?
EDIT
After rewriting code from Guillaume Michel's answer with the use of functions defined in library I'm using (I do not use HAL library), I came up with a code
TIM_TimeBaseInitTypeDef timer4;
timer4.TIM_Prescaler=0;
timer4.TIM_CounterMode=TIM_CounterMode_Up;
timer4.TIM_Period=5;
timer4.TIM_ClockDivision=TIM_CKD_DIV1;
TIM_TimeBaseInit(TIM4,&timer4);
TIM_ETRClockMode2Config(TIM4,TIM_ExtTRGPSC_DIV2,TIM_ExtTRGPolarity_NonInverted, 0);
TIM_SelectSlaveMode(TIM4,TIM_SlaveMode_Reset);
TIM_SelectMasterSlaveMode(TIM4, TIM_MasterSlaveMode_Disable);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_PinAFConfig(GPIOD,GPIO_Pin_13,GPIO_AF_TIM4);
GPIO_Init(GPIOD, &GPIO_InitStructure);
This is compilable, yet non-working code. I set the timer period to 5 and I set interrupt to toggle LED every time timer counts all the way up, but LED never lights on no matter how many times i run magnet around sensor. Is there some visible mistake? What can I do to make it work?

Answer 1

You could try to connect the hall sensor output on a GPIO of you STM32F411 and set this GPIO as clock of the timer. This could look like:
TIM_HandleTypeDef htim4;
TIM_ClockConfigTypeDef sClockSourceConfig;
TIM_MasterConfigTypeDef sMasterConfig;
htim4.Instance = TIM4;
htim4.Init.Prescaler = 0;
htim4.Init.CounterMode = TIM_COUNTERMODE_UP;
htim4.Init.Period = 65535;
htim4.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
HAL_TIM_Base_Init(&htim4);
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_ETRMODE2;
sClockSourceConfig.ClockPolarity = TIM_CLOCKPOLARITY_NONINVERTED;
sClockSourceConfig.ClockPrescaler = TIM_CLOCKPRESCALER_DIV1;
sClockSourceConfig.ClockFilter = 0;
HAL_TIM_ConfigClockSource(&htim4, &sClockSourceConfig);
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
HAL_TIMEx_MasterConfigSynchronization(&htim4, &sMasterConfig);
The GPIO is set up like this:
//Set PE0 as TIM4_ETR
__HAL_RCC_GPIOE_CLK_ENABLE();
GPIO_InitTypeDef GPIO_InitStruct;
GPIO_InitStruct.Pin = GPIO_PIN_0;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
GPIO_InitStruct.Alternate = GPIO_AF2_TIM4;
HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);