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STM32F3 Discovery Quadrature Encoding

mattfox
Associate II
Posted on June 21, 2013 at 22:44

I'm working on getting quadrature encoding working through either TIM1 or TIM8.  I searched the past topics on this forum, but I can't tell how mine is different/ why it isn't working.  I'm using USART to debug the count, and I'm consistently getting a counter value of 0, though I can tell my input is valid.  

Can anyone see what i'm doing wrong in this code?  Thanks so much for taking the time to look at it.

/*

 * main.c

 *

 *  Created on: Jun 20, 2013

 */

&sharpinclude ''main.h''

&sharpinclude ''common.h''

&sharpinclude ''usart.h''

&sharpinclude ''peripherals.h''

static void TIM_Config(void);

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

uint32_t a=0;

uint16_t i;

int main(void)

{

/* Initialize USART2 */

USART2_Init(115200, TRUE);

printf(''\fUART2 initialized\n\r'');

TIM_Config();

/* TIM1 clock enable */

RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8 , ENABLE);

/* Time Base configuration */

TIM_TimeBaseStructure.TIM_Prescaler = 0;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_CenterAligned1;

TIM_TimeBaseStructure.TIM_Period = 0xFFFF;

TIM_TimeBaseStructure.TIM_ClockDivision = 0;

TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

//Configure the encoder interface

TIM_EncoderInterfaceConfig(TIM8, TIM_EncoderMode_TI12, TIM_ICPolarity_BothEdge, TIM_ICPolarity_BothEdge);

TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);

TIM_ARRPreloadConfig(TIM8, ENABLE);

/* TIM1 counter enable */

TIM_Cmd(TIM8, ENABLE);

//Counter loop

while(1)

{

printf(''Counter: %d\n\r'', (uint16_t)(TIM1->CNT & 0x0000ffff));

for(i=0; i<30000; i++)

{

a++;

a = a%5;

}

}

return 0;

}

static void TIM_Config(void)

{

GPIO_InitTypeDef GPIO_InitStructure;

/* GPIOA, GPIOB and GPIOE Clocks enable */

RCC_AHBPeriphClockCmd( RCC_AHBPeriph_GPIOA | RCC_AHBPeriph_GPIOC, ENABLE);

//RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8, ENABLE);

//RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);

//Configure pins

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

GPIO_Init(GPIOC, &GPIO_InitStructure);

GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_4);  //C6 -TIM1_CH1

GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_4);  //C7  TIM1_CH2

// GPIO_Init(GPIOC, &GPIO_InitStructure);

// GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_2);  //C6 -TIM1_CH1

// GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_2);  //C7  TIM1_CH2

}

&sharpifdef  USE_FULL_ASSERT

/**

 * @brief  Reports the name of the source file and the source line number

 *         where the assert_param error has occurred.

 * @param  file: pointer to the source file name

 * @param  line: assert_param error line source number

 * @retval None

 */

void assert_failed(uint8_t* file, uint32_t line)

{

/* User can add his own implementation to report the file name and line number,

     ex: printf(''Wrong parameters value: file %s on line %d\r\n'', file, line) */

/* Infinite loop */

while (1)

{

}

}

&sharpendif

#input-capture #quadrature-encoder
15 REPLIES 15
mattfox
Associate II
Posted on June 24, 2013 at 18:09

I figured out that I had a bug in my arduino code which is why I only counted up 4.  Now I'm having an error where the counter will not count upwards correctly, but will could downwards accurately.  I keep getting a variable count up (but around 2x the number of rotations using only one rising edge) but exactly 2x the number of rotations down.  Any ideas?

mattfox
Associate II
Posted on June 24, 2013 at 22:00

Another update:  I got the functionality above using TIM_EncoderMode_TI1, TIM_ICPolarity_Rising, TIM_ICPolarity_Rising

If I use falling, or switch to TIM_EncoderMode_TI2 rising or falling, I get incorrect numbers for both counting upwards and downwards.  I have yet to figure out why this could be.  I tried switching to TIM 1 and switching the input pins to PC8 and 9 but I didn't get a reading out.  I also don't get a reading out for TIM_EncoderMode_T12.  Any ideas would be much appreciated!

mattfox
Associate II
Posted on June 25, 2013 at 20:24

Final update:  I finally got it working.  Really stupid error on my part.  My arduino outputs 5 volts, so I set up a voltage divider before attaching it to the discovery board.  I assumed that 3 volts would be close enough to 3.3 volts that the board runs on to be sufficient for anything that I needed, but it turns out that 3 V is right on the limit of the board's capabilities, so i would not always catch the rising edge of the encoder.  I redid the voltage divider to set it around 3.3 volts and everything works.

Thanks so much for helping!! I definitely needed it.  

hendalage
Associate II
Posted on July 27, 2013 at 21:17

Hi,

I'm new to the STM and I just want to configure the quadrature encoder on Timer2 of my stm32f3 discovery board. the programming manual says that two encoder inputs are captured from TI1 and TI2 pins. but i cant find such an alternate function on any pin of the microcontroller. so can anyone tell me which pins i should use to connect the encoder and in which mode of the Timer2?

Thank You!

Posted on July 27, 2013 at 22:06

You'd want to use some uncommitted pins designated for TIM2_CH1 and TIM2_CH2, see Data Sheet/Manual for the specific part involved.

This thread has a TIM2 example at the end.

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hendalage
Associate II
Posted on July 28, 2013 at 07:10

Thank you very much :) it helped a lot ^^