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mehmet.karakaya
mehmet.karakaya
Associate III
October 20, 2013
Question

help! - I couldnot get stm32f4 timer work in encoder mode

  • October 20, 2013
  • 7 replies
  • 1393 views
Posted on October 20, 2013 at 19:17

hello dear forum,

I am trying to read an AB encoder with stm32f4 timer_1 I got the encoder signals through 75175 to timer_1_ch1 and ch2 pins I can see square waves of A and B with osciloscope the codes are below - any help appreciated - thank you 

void
Encoderinit(
void
) { 
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE); 
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9|GPIO_Pin_11; 
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; 
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; 
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz; 
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; 
GPIO_Init(GPIOE, &GPIO_InitStructure); 
GPIO_PinAFConfig(GPIOE,GPIO_PinSource9,GPIO_AF_TIM1); 
GPIO_PinAFConfig(GPIOE,GPIO_PinSource11,GPIO_AF_TIM1); 
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 0xffff; 
TIM_TimeBaseStructure.TIM_Prescaler = 0; 
TIM_TimeBaseStructure.TIM_ClockDivision = 0; 
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; 
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure); 
TIM_EncoderInterfaceConfig(TIM1,TIM_EncoderMode_TI12,TIM_ICPolarity_Rising,TIM_ICPolarity_Rising ); 
TIM_ITConfig(TIM1,TIM_IT_Update , ENABLE); 
TIM_Cmd(TIM1, ENABLE); 
TIM1->CNT=0; 
}

and in the main loop I read enkoder 100 times a second but always value 0 

main{ 
.................. 
Encoderinit() 
.................. 
while
(1){ 
.................. 
enkoder=TIM1->CNT; 
}

#tim-encoder #tim-encoder #stm32f4-timer-encoder
This topic has been closed for replies.

7 replies

mehmet.karakaya
mehmet.karakayaAuthor
Associate III
October 20, 2013
Posted on October 20, 2013 at 21:07

hello - the problem solved

Tesla DeLorean
Tesla DeLorean
Guru
October 20, 2013
Posted on October 20, 2013 at 21:53

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);

??

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mehmet.karakaya
mehmet.karakayaAuthor
Associate III
October 21, 2013
Posted on October 21, 2013 at 14:23

hello - the problem is solved

it was a mistake of me while reading the TIM1->CNT

the above initialization code is correct for anyone who is searching for help in this issue

with this occasion I want to ask

if I can program the input capture filter IC1F , IC2F 

(TIMx_CCMR1)

 

while the timer is in encoder mode ?

I mean is the input capture filter active in encoder mode ?

thank you  

jpeacock2399
jpeacock2399
Associate III
October 21, 2013
Posted on October 21, 2013 at 15:47

Yes you can enable captures in encoder mode.  I use capture on CC1 to detect when the encoder count changes and on CC3 to detect the index.

  Jack Peacock
mehmet.karakaya
mehmet.karakayaAuthor
Associate III
October 21, 2013
Posted on October 21, 2013 at 18:26

hello thank you for the answers

what I want ask is ,

there is filter at the input stage of timer inputs to eliminate fals triggering

it is sampling the timer input and if it is always ''1''  for example for a period of programmed filter time the timer only then captures or counts ( sorry this is my best english hope you understand )

what I want ask is is this filter active when in encoder mode ? ( IC1F IC2F ) CCMR register

the manual says:

IC1F[3:0]

 

: Input capture 1 filter

 

This bit-field defines the frequency used to sample TI1 input and the length of the digital filter applied

to TI1. The digital filter is made of an event counter in which N events are needed to validate a

transition on the output

 

Yes you can enable captures in encoder mode.  I use capture on CC1 to detect when the encoder count changes and on CC3 to detect the index.

  Jack Peacock
Tesla DeLorean
Tesla DeLorean
Guru
October 21, 2013
Posted on October 21, 2013 at 18:35

The pins are feed though a synchronizer, likely at the pin by the AHB clocks, and then by the TIM at it's APB/TIM clock. You'd have to digest the docs.

Filter elements of the TIM are controlled at a rate specified by 

TIM_TimeBaseStructure.TIM_ClockDivision

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jpeacock2399
jpeacock2399
Associate III
October 21, 2013
Posted on October 21, 2013 at 21:16

Yes the digital filter is used in encoder mode, and it does make a difference.  My setup is a single-ended Avago HEDS-5540 optical encoder on the end of a NEMA 17 or 23 stepper, with 800 count wheels (2x sampling for 400 half setps on a 1.8 degree motor). 

Some ad hoc experimenting gave a good reading at digital filter set to 5, not so good at 7.  This is on an STM32F405 at 168MHz, using TIM4 for a rotary encoder and TIM5 for linear encoder.

  Jack Peacock
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