TIM3 CH2 external counter configuration

Question

Posted on April 10, 2018 at 14:55Hi!I want to use an external clock signal for timing. This clock signal is ~130 kHz. I want to count N pulses with a timer and I want an IRQ after N pulses. For this purpose I'd like to use TIM3 in external counter mode 1. The input pin is PC7 which is TIM3_CH2 in alternate function 2. I'm using the LL driver. So far I came up with this but it's not working no matter what value I write in to the ARR register. This code is based on several examples in CUBE_FW_L4 and other web sources. I know that there are lots of code out there but it seems that people are using different drivers like standard, HAL etc. I call timing_init_timing() function to configure the pins, timer etc. The function timing_set_ARR is used from a command terminal and I get zero calling timing_get_counter() function and the timcnt readout is always 1.I already had my laps on reference manual but I really not get the concept as the driver is using confusing names which I couldn't found in the RM of the MCU. I'm missing some points probably so any help would be great.void timing_configure_input_pin(void) {  // Clock  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOC);  // TIM3 configuration on GPIO PC7, alternate function 2  LL_GPIO_SetPinMode(GPIOC, LL_GPIO_PIN_7, LL_GPIO_MODE_ALTERNATE);  LL_GPIO_SetPinPull(GPIOC, LL_GPIO_PIN_7, LL_GPIO_PULL_DOWN);  LL_GPIO_SetPinSpeed(GPIOC, LL_GPIO_PIN_7, LL_GPIO_SPEED_FREQ_HIGH);  LL_GPIO_SetAFPin_0_7(GPIOC, LL_GPIO_PIN_7, LL_GPIO_AF_2);}void timing_configure_nvic(void) {  NVIC_SetPriority(TIM3_IRQn, 0);  NVIC_EnableIRQ(TIM3_IRQn);}void timing_configure_timer(void) {  // Clock  LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_TIM3);  LL_TIM_IC_SetFilter(TIM3, LL_TIM_CHANNEL_CH2, LL_TIM_IC_FILTER_FDIV1);  LL_TIM_IC_SetPrescaler(TIM3, LL_TIM_CHANNEL_CH2, LL_TIM_ICPSC_DIV8);  LL_TIM_IC_SetPolarity(TIM3, LL_TIM_CHANNEL_CH2, LL_TIM_IC_POLARITY_RISING);  LL_TIM_IC_SetActiveInput(TIM3, LL_TIM_CHANNEL_CH2, LL_TIM_ACTIVEINPUT_DIRECTTI);  LL_TIM_SetClockSource(TIM3, LL_TIM_CLOCKSOURCE_EXT_MODE1);  LL_TIM_CC_EnableChannel(TIM3, LL_TIM_CHANNEL_CH2);  LL_TIM_EnableIT_UPDATE(TIM3);  LL_TIM_GenerateEvent_UPDATE(TIM3);}void timing_set_ARR(uint16_t val) {  LL_TIM_SetAutoReload(TIM3, val);  }uint32_t timing_get_counter(void) {  return LL_TIM_GetCounter(TIM3);}void timing_init_timing(void) {  timing_configure_input_pin();  timing_configure_nvic();  timing_configure_timer();}void TIM3_IRQHandler(void) {  if(LL_TIM_IsActiveFlag_UPDATE(TIM3) == 1) {    // Clear the update interrupt flag    LL_TIM_ClearFlag_UPDATE(TIM3);    board_toggle_NUCLEO_LED();    timcnt++;  }}

Gergo Santha · Accepted Answer

Posted on April 11, 2018 at 12:18Okay, I converted a code based on Std Periph library to direct register read/write and it is working now. I paste the code here. The input signal is ~130209 Hz connected to PC7 of STM32L476RG from SPIRIT1 XO, 25e6 MHz/192.void timing_configure_input_pin(void) { /* Enable the peripheral clock of GPIOs */ LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOC); /* GPIO TIM3_CH2 configuration */ LL_GPIO_SetPinMode(GPIOC, LL_GPIO_PIN_7, LL_GPIO_MODE_ALTERNATE); LL_GPIO_SetPinPull(GPIOC, LL_GPIO_PIN_7, LL_GPIO_PULL_DOWN); LL_GPIO_SetPinSpeed(GPIOC, LL_GPIO_PIN_7, LL_GPIO_SPEED_FREQ_HIGH); LL_GPIO_SetAFPin_0_7(GPIOC, LL_GPIO_PIN_7, LL_GPIO_AF_2);}void timing_configure_nvic(void) { NVIC_SetPriority(SPIRIT1_XO_OUT_TIMER_CC_IRQn, 0); NVIC_EnableIRQ(SPIRIT1_XO_OUT_TIMER_CC_IRQn);}void timing_ti2_config(void) { // Temporary variables uint16_t tmpccmr1 = 0, tmpccer = 0, tmp = 0; /* Disable the Channel 2: Reset the CC2E Bit */ TIM3->CCER &= (uint16_t)~TIM_CCER_CC2E; tmpccmr1 = TIM3->CCMR1; tmpccer = TIM3->CCER; tmp = (uint16_t)(0x00 << 4); // TIM_ICPolarity_Rising = ((uint16_t)0x0000) /* Select the Input and set the filter */ tmpccmr1 &= ((uint16_t)~TIM_CCMR1_CC2S) & ((uint16_t)~TIM_CCMR1_IC2F); tmpccmr1 |= (uint16_t)(0x00 << 12); // TIM_ICFilter: must be a value between 0x00 and 0x0F. tmpccmr1 |= (uint16_t)(0x0002 << 8); //CC2S[1:0] 10: CC2 channel is configured as input, IC2 is mapped on TI1 /* Select the Polarity and set the CC2E Bit */ tmpccer &= (uint16_t)~(TIM_CCER_CC2P | TIM_CCER_CC2NP); tmpccer |= (uint16_t)(tmp | (uint16_t)TIM_CCER_CC2E); /* Write to TIMx CCMR1 and CCER registers */ TIM3->CCMR1 = tmpccmr1 ; TIM3->CCER = tmpccer;}void timing_select_input_trigger(void) { uint16_t tmpsmcr = 0; /* Get the TIM3 SMCR register value */ tmpsmcr = TIM3->SMCR; /* Reset the TS Bits */ tmpsmcr &= (uint16_t)~TIM_SMCR_TS; /* Set the Input Trigger source */ tmpsmcr |= (uint16_t)0x0060; // TS[6:4] 110: Filtered Timer Input 2 (TI2FP2) /* Write to TIMx SMCR */ TIM3->SMCR = tmpsmcr;}void timing_configure_timer(void) { SPIRIT1_XO_OUT_TIMER_CC_CLK_ENABLE(); // CMS = b00 (counter counts up/down depending on DIR bit // DIR = b0 counter upcounter // CKD = b00 TIM3->CR1 &=~(TIM_CR1_DIR | TIM_CR1_CMS | TIM_CR1_CKD); // Set ARR value (period) TIM3->ARR = 1; // Set prescaler TIM3->PSC = 1301; // The counter clock frequency CK_CNT is equal to f CK_PSC / (PSC[15:0] + 1) timing_ti2_config(); timing_select_input_trigger(); TIM3->SMCR |= (uint16_t)0x0007; // TIM_SlaveMode_External1 = ((uint16_t)0x0007) TIM3->DIER |=TIM_DIER_UIE; TIM3->CR1 |= TIM_CR1_CEN;}void timing_init_timing(void) { timing_configure_input_pin(); timing_configure_nvic(); timing_configure_timer(); }void SPIRIT1_XO_OUT_TIMER_IRQ_HANDLER(void){ if(LL_TIM_IsActiveFlag_UPDATE(SPIRIT1_XO_OUT_TIMER) == 1) { /* Clear the update interrupt flag*/ LL_TIM_ClearFlag_UPDATE(SPIRIT1_XO_OUT_TIMER); board_toggle_NUCLEO_LED(); timcnt++; }}

henry.dick · Answer

Posted on April 10, 2018 at 15:35A few ways of doing it.1. For a count up counter, load the counter with -N and use the overflow interrupt.2. For count down counter, load the counter with initial value of N and overflow interrupt.3. Set the compare match at N and use the cc interrupt.4. Use a Pressler of 129, and load the counter with -1.....The possibility is simply endless.

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