how to use Index Track in quadrature encoder mode

jveith · ‎2012-12-26

Posted on December 26, 2012 at 18:15

have 2 timer channels (CH1+CH2) setup in quadrature encoder mode and all things work fine. The encoder (Avago HEDS 5540) has a third index channel with very narrow pulse per revolution. Is ist possible to use this signal for timer Reset or Prelaod event ? What input pin is required ? (ETR?) The CH1/2 input Frequency is above 100khz and software interrupt delay seems too slow

mehmet.karakaya · ‎2012-12-27

Posted on December 27, 2012 at 12:28

you can connect index puls to an EXTI interrupt

and this way you can zero the encoder counter

like reference mode in a CNC machine

jveith · ‎2012-12-28

Posted on December 28, 2012 at 13:20

same hint is already in STM32 datasheet: '' The 3rd

(encoder) output may be connected to EXTI and trigger a Counter reset.

My problem is, that EXTI calls a interupt service function what modifies the counter per instruction what is much to slow. Slave mode = Reset Mode is contrary to Encoder mode of a counter. How to connect reset / preload to external signal in Encoder mode ? (The Xmega can do this)

asiflion02 · ‎2013-01-01

Posted on January 01, 2013 at 12:23

This is how i have configured timer to read encoder pulses,but the counter doesnt seem to increment ,is it anything else i have to change in this..?

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC,ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8,ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_Init(GPIOC,&GPIO_InitStructure);

GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_TIM8);

GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_TIM8);

TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);

TIM_TimeBaseStructure.TIM_Period =2500;

TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);

TIM_EncoderInterfaceConfig(TIM8, TIM_EncoderMode_TI12, TIM_ICPolarity_Rising, TIM_ICPolarity_Rising);

NVIC_InitStructure.NVIC_IRQChannel = TIM8_UP_TIM13_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

TIM_ITConfig(TIM8, TIM_IT_Update, ENABLE);

TIM_Cmd(TIM8, ENABLE);