Hi ,
I am using TIM21 in input capture mode to measure the LSI frequency (~37 kHz). However, when I set the TIM21 clock to 2 MHz or use the MSI clock, it causes a hardware fault when attempting to capture the LSI frequency.
I have reviewed the STM32CubeL0 example code for RTC_LSI, which uses an MSI clock set to 2 MHz to measure the LSI frequency successfully. However, in my case, this setup does not work, and I am not sure why.
Thanks!
STM32CubeL0 example code to measure LSI:
/**
******************************************************************************
* @file RTC/RTC_LSI/Src/main.c
* @author MCD Application Team
* @brief This sample code shows how to use STM32L0xx RTC HAL API to
* use the LSI clock source auto calibration to get a precise RTC
* clock.
******************************************************************************
* @attention
*
* <h2><center>© Copyright (c) 2016 STMicroelectronics.
* All rights reserved.</center></h2>
*
* This software component is licensed by ST under BSD 3-Clause license,
* the "License"; You may not use this file except in compliance with the
* License. You may obtain a copy of the License at:
* opensource.org/licenses/BSD-3-Clause
*
******************************************************************************
*/
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/** @addtogroup STM32L0xx_HAL_Examples
* @{
*/
/** @addtogroup RTC_LSI
* @{
*/
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define WAKEUP_TIMER_ENABLE 0x32F2
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
RTC_HandleTypeDef RtcHandle;
TIM_HandleTypeDef Input_Handle;
uint16_t tmpCCTIM_CHANNEL_1[2] = {0, 0};
__IO uint32_t uwLsiFreq = 0;
__IO uint32_t uwCaptureNumber = 0;
__IO uint32_t uwPeriodValue = 0;
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void RTC_Config(void);
static uint32_t GetLSIFrequency(void);
/* Private functions ---------------------------------------------------------*/
/**
* @brief Main program
* @PAram None
* @retval None
*/
int main(void)
{
GPIO_InitTypeDef GPIO_InitStruct;
/* STM32L0xx HAL library initialization:
- Configure the Flash prefetch, Flash preread and Buffer caches
- Systick timer is configured by default as source of time base, but user
can eventually implement his proper time base source (a general purpose
timer for example or other time source), keeping in mind that Time base
duration should be kept 1ms since PPP_TIMEOUT_VALUEs are defined and
handled in milliseconds basis.
- Low Level Initialization
*/
HAL_Init();
/* Configure the system clock to 2 MHz */
SystemClock_Config();
/* Configure LED3 */
BSP_LED_Init(LED3);
/* Configure PA.12 (Arduino D2) button */
GPIO_InitStruct.Pin = GPIO_PIN_12;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
/* Enable GPIOA clock */
__HAL_RCC_GPIOA_CLK_ENABLE();
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/* RTC Configuration -------------------------------------------------------*/
RTC_Config();
/* Wait Until PA.12 (Arduino D2) is connected to GND */
while(HAL_GPIO_ReadPin(GPIOA, GPIO_PIN_12) == GPIO_PIN_SET)
{
}
/* Wait Until PA.12 (Arduino D2) is released to 3.3V */
while(HAL_GPIO_ReadPin(GPIOA, GPIO_PIN_12) == GPIO_PIN_RESET)
{
}
/* Get the LSI frequency: TIM21 is used to measure the LSI frequency */
uwLsiFreq = GetLSIFrequency();
/* Update the Calendar Configuration with the LSI exact value */
RtcHandle.Init.HourFormat = RTC_HOURFORMAT_24;
RtcHandle.Init.AsynchPrediv = 0x7F;
RtcHandle.Init.SynchPrediv = (uwLsiFreq/128) - 1;
RtcHandle.Init.OutPut = RTC_OUTPUT_DISABLE;
RtcHandle.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
RtcHandle.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
if(HAL_RTC_Init(&RtcHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/* Infinite loop */
while (1)
{
}
}
/**
* @brief System Clock Configuration
* The system Clock is configured as follow :
* System Clock source = MSI
* SYSCLK(Hz) = 2000000
* HCLK(Hz) = 2000000
* AHB Prescaler = 1
* APB1 Prescaler = 1
* APB2 Prescaler = 1
* Flash Latency(WS) = 0
* Main regulator output voltage = Scale3 mode
* @retval None
*/
void SystemClock_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
/* Enable MSI Oscillator */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
RCC_OscInitStruct.MSIState = RCC_MSI_ON;
RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_5;
RCC_OscInitStruct.MSICalibrationValue=0x00;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct)!= HAL_OK)
{
/* Initialization Error */
while(1);
}
/* Select MSI as system clock source and configure the HCLK, PCLK1 and PCLK2
clocks dividers */
RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0)!= HAL_OK)
{
/* Initialization Error */
while(1);
}
/* Enable Power Control clock */
__HAL_RCC_PWR_CLK_ENABLE();
/* The voltage scaling allows optimizing the power consumption when the device is
clocked below the maximum system frequency, to update the voltage scaling value
regarding system frequency refer to product datasheet. */
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE3);
}
/**
* @brief This function is executed in case of error occurrence.
* @PAram None
* @retval None
*/
void Error_Handler(void)
{
while (1)
{
}
}
/**
* @brief Configure the RTC peripheral by selecting the clock source.
* @PAram None
* @retval None
*/
static void RTC_Config(void)
{
/*##-1- Configure the RTC peripheral #######################################*/
/* Configure RTC prescaler and RTC data registers */
/* RTC configured as follows:
- Hour Format = Format 24
- Asynch Prediv = Value according to source clock
- Synch Prediv = Value according to source clock
- OutPut = Output Disable
- OutPutPolarity = High Polarity
- OutPutType = Open Drain */
RtcHandle.Instance = RTC;
RtcHandle.Init.HourFormat = RTC_HOURFORMAT_24;
RtcHandle.Init.AsynchPrediv = RTC_ASYNCH_PREDIV; /* 0x7F */
RtcHandle.Init.SynchPrediv = RTC_SYNCH_PREDIV; /* (39KHz / 128) - 1 = 0x130 */
RtcHandle.Init.OutPut = RTC_OUTPUT_DISABLE;
RtcHandle.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
RtcHandle.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
if(HAL_RTC_Init(&RtcHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/*##-2- Check if data stored in BackUp register1: Wakeup timer enable #######*/
/* Read the Back Up Register 1 Data */
if (HAL_RTCEx_BKUPRead(&RtcHandle, RTC_BKP_DR1) == WAKEUP_TIMER_ENABLE)
{
/* if the wakeup timer is enabled then deactivate it to disable the wakeup timer interrupt */
if(HAL_RTCEx_DeactivateWakeUpTimer(&RtcHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
}
/*##-3- Configure the RTC Wakeup peripheral #################################*/
/* Setting the Wakeup time to 1 s
If RTC_WAKEUPCLOCK_CK_SPRE_16BITS is selected, the frequency is 1Hz,
this allows to get a wakeup time equal to 1 s if the counter is 0x0 */
HAL_RTCEx_SetWakeUpTimer_IT(&RtcHandle, 0x0, RTC_WAKEUPCLOCK_CK_SPRE_16BITS);
/*##-4- Write 'wakeup timer enabled' tag in RTC Backup data Register 1 #######*/
HAL_RTCEx_BKUPWrite(&RtcHandle, RTC_BKP_DR1, WAKEUP_TIMER_ENABLE);
}
/**
* @brief Configures TIM21 to measure the LSI oscillator frequency.
* @PAram None
* @retval LSI Frequency
*/
static uint32_t GetLSIFrequency(void)
{
TIM_IC_InitTypeDef TIMInput_Config;
/* Configure the TIM peripheral *********************************************/
/* Set TIMx instance */
Input_Handle.Instance = TIM21;
/* TIM21 configuration: Input Capture mode ---------------------
The LSI oscillator is connected to TIM21 TIM_CHANNEL_1.
The Rising edge is used as active edge.
The TIM21 Capture/Compare register associated to TIM_CHANNEL_1
is used to compute the frequency value.
------------------------------------------------------------ */
Input_Handle.Init.Prescaler = 0;
Input_Handle.Init.CounterMode = TIM_COUNTERMODE_UP;
Input_Handle.Init.Period = 0xFFFF;
Input_Handle.Init.ClockDivision = 0;
if(HAL_TIM_IC_Init(&Input_Handle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/* Connect internally the TIM21 Input Capture of TIM_CHANNEL_1 to the LSI clock output */
HAL_TIMEx_RemapConfig(&Input_Handle, TIM21_TI1_LSI);
/* Configure the Input Capture of TIM_CHANNEL_1 */
TIMInput_Config.ICPolarity = TIM_ICPOLARITY_RISING;
TIMInput_Config.ICSelection = TIM_ICSELECTION_DIRECTTI;
TIMInput_Config.ICPrescaler = TIM_ICPSC_DIV8;
TIMInput_Config.ICFilter = 0;
if(HAL_TIM_IC_ConfigChannel(&Input_Handle, &TIMInput_Config, TIM_CHANNEL_1) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/* Start the TIM Input Capture measurement in interrupt mode */
if(HAL_TIM_IC_Start_IT(&Input_Handle, TIM_CHANNEL_1) != HAL_OK)
{
Error_Handler();
}
/* Wait until the TIM21 gets 2 LSI edges */
while(uwCaptureNumber != 2)
{
}
/* Disable TIM21 Capture/Compare channel Interrupt Request */
HAL_TIM_IC_Stop_IT(&Input_Handle, TIM_CHANNEL_1);
/* Deinitialize the TIM21 peripheral registers to their default reset values */
HAL_TIM_IC_DeInit(&Input_Handle);
return uwLsiFreq;
}
/**
* @brief Input Capture callback in non blocking mode
* @PAram htim : TIM IC handle
* @retval None
*/
void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim)
{
/* Get the Input Capture value */
tmpCCTIM_CHANNEL_1[uwCaptureNumber++] = HAL_TIM_ReadCapturedValue(&Input_Handle, TIM_CHANNEL_1);
if (uwCaptureNumber >= 2)
{
if ( tmpCCTIM_CHANNEL_1[0] > tmpCCTIM_CHANNEL_1[1] )
{
/* Compute the period length */
uwPeriodValue = (uint16_t)(0xFFFF - tmpCCTIM_CHANNEL_1[0] + tmpCCTIM_CHANNEL_1[1] + 1);
}
else
{
/* Compute the period length */
uwPeriodValue = (uint16_t)(tmpCCTIM_CHANNEL_1[1] - tmpCCTIM_CHANNEL_1[0]);
}
/* Frequency computation */
uwLsiFreq = (uint32_t) SystemCoreClock / uwPeriodValue;
uwLsiFreq *= 8;
}
}
/**
* @brief RTC wakeup timer callback
* @PAram htim : TIM IC handle
* @retval None
*/
void HAL_RTCEx_WakeUpTimerEventCallback(RTC_HandleTypeDef *hrtc)
{
/* Toggle LED3 */
BSP_LED_Toggle(LED3);
}
#ifdef 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)
{
}
}
#endif
/**
* @}
*/
/**
* @}
*/
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
This is my clock configuration:
My timer21 configuration:
/* USER CODE END TIM21_Init 1 */
htim21.Instance = TIM21;
htim21.Init.Prescaler = 0;
htim21.Init.CounterMode = TIM_COUNTERMODE_UP;
htim21.Init.Period = 65535;
htim21.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim21.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
if (HAL_TIM_Base_Init(&htim21) != HAL_OK)
{
Error_Handler();
}
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
if (HAL_TIM_ConfigClockSource(&htim21, &sClockSourceConfig) != HAL_OK)
{
Error_Handler();
}
if (HAL_TIM_IC_Init(&htim21) != HAL_OK)
{
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim21, &sMasterConfig) != HAL_OK)
{
Error_Handler();
}
sConfigIC.ICPolarity = TIM_INPUTCHANNELPOLARITY_RISING;
sConfigIC.ICSelection = TIM_ICSELECTION_DIRECTTI;
sConfigIC.ICPrescaler = TIM_ICPSC_DIV8;
sConfigIC.ICFilter = 0;
if (HAL_TIM_IC_ConfigChannel(&htim21, &sConfigIC, TIM_CHANNEL_1) != HAL_OK)
{
Error_Handler();
}
if (HAL_TIMEx_RemapConfig(&htim21, TIM21_TI1_LSI) != HAL_OK)
{
Error_Handler();
}
