STM32 Rotary Encoder config on TIM4

Question

I'm trying to use TIM4 for quadrature encoder input on my STM32F4DISCOVERY board. Here is my code :

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

GPIO_InitTypeDef GPIO_InitStructure;
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_InitStructure.GPIO_Pin = GPIO_Pin_6| GPIO_Pin_7;
GPIO_Init(GPIOB, &GPIO_InitStructure);

GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_TIM4);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_TIM4);

/* Configure the timer */
TIM_EncoderInterfaceConfig(TIM4, TIM_EncoderMode_TI12, TIM_ICPolarity_Rising, TIM_ICPolarity_Rising);

/* TIM4 counter enable */
TIM_Cmd(TIM4, ENABLE);

sadly, the TIM4->CNT counter won't move when I turn the encoder. I works perfectly with TIM8. Here is the full code of the working TIM8 and the not working TIM4 : https://gist.github.com/nraynaud/5082298

I check by printing rT2() in gdb after moving the encoder by hand.

Answer 1

I have used an STM32F407 to read encoder counts from 3 optical encoders. I am using ChibiOS RTOS so the timer struct is slightly different from the ST Peripheral library timer struct, but the information is basically the same. Here is how I configure the registers of the actual timers:

stm32_tim_t * encoderTimers[3] = {STM32_TIM8, STM32_TIM3, STM32_TIM4};
for (auto timer : encoderTimers) {
  timer->SMCR = 3;          // Encoder mode 3
  timer->CCER = 0;          // rising edge polarity
  timer->ARR = 0xFFFF;      // count from 0-ARR or ARR-0
  timer->CCMR1 = 0xC1C1;    // f_DTS/16, N=8, IC1->TI1, IC2->TI2
  timer->CNT = 0;           // Initialize counter
  timer->EGR = 1;           // Generate an update event
  timer->CR1 = 1;           // Enable the counter
}

Also, make sure you enable the timer peripherals in the APB1 or APB2 registers of the RCC. Something like:

RCC->APB1ENR |= ((1 <<  2)  // TIM4  --  Front wheel angle measurement
             |   (1 <<  1));// TIM3  --  Steer angle measurement

Finally, you need to make sure you configure the GPIO settings correctly. This means configuring the GPIO for Alternate Function.

Answer 2

encoder with standard driver

#include "mbed.h"
#include "stm32f4xx.h"
#include "stm32f4xx_hal_tim_ex.h"

TIM_HandleTypeDef timer;
TIM_Encoder_InitTypeDef encoder;

//direction to PA_9 -- step pulse to PA_8

int main(){
     GPIO_InitTypeDef GPIO_InitStruct;
        __TIM1_CLK_ENABLE();
        __GPIOA_CLK_ENABLE();
        GPIO_InitStruct.Pin = GPIO_PIN_8 | GPIO_PIN_9;
        GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
        GPIO_InitStruct.Pull = GPIO_PULLDOWN;
        GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
        GPIO_InitStruct.Alternate = GPIO_AF1_TIM1;
        HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    timer.Instance = TIM1;
    timer.Init.Period = 0xffff;
    timer.Init.Prescaler = 0;
    timer.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
    timer.Init.CounterMode = TIM_COUNTERMODE_UP;

    encoder.EncoderMode = TIM_ENCODERMODE_TI12; 
    encoder.IC1Filter = 0x0f;
    encoder.IC1Polarity = TIM_INPUTCHANNELPOLARITY_RISING; 
    encoder.IC1Prescaler = TIM_ICPSC_DIV4;
    encoder.IC1Selection = TIM_ICSELECTION_DIRECTTI;

    encoder.IC2Filter = 0x0f;
    encoder.IC2Polarity = TIM_INPUTCHANNELPOLARITY_FALLING;    
    encoder.IC2Prescaler = TIM_ICPSC_DIV4;
    encoder.IC2Selection = TIM_ICSELECTION_DIRECTTI;

    HAL_TIM_Encoder_Init(&timer, &encoder);
    HAL_TIM_Encoder_Start(&timer,TIM_CHANNEL_1);   


    TIM1->EGR = 1;           // Generate an update event
    TIM1->CR1 = 1;           // Enable the counter


 while (1) {
        int16_t count1; 
        count1=TIM1->CNT; 

        printf("%d\r\n", count1);
        wait(1.0);

 };
}

Answer 3

You may need to use pull ups for input unless you are using external resistors or powering the encoder. I usually connect encoder to ground and use internal pull ups to set idle state.