/**
* @brief USB Clock Configuration: Enable Resources
* @param None
* @retval None
*/
void USBClock_Enable(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_PeriphCLKInitTypeDef PeriphClkInitStruct;
static RCC_CRSInitTypeDef RCC_CRSInitStruct;
/* Enable HSI48 Oscillator to be used as USB clock source */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI48;
RCC_OscInitStruct.HSI48State = RCC_HSI48_ON;
HAL_RCC_OscConfig(&RCC_OscInitStruct);
/* Select HSI48 as USB clock source */
PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_USB;
PeriphClkInitStruct.UsbClockSelection = RCC_USBCLKSOURCE_HSI48;
HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct);
/*Configure the clock recovery system (CRS)**********************************/
/*Enable CRS Clock*/
__HAL_RCC_CRS_CLK_ENABLE();
/* Default Synchro Signal division factor (not divided) */
RCC_CRSInitStruct.Prescaler = RCC_CRS_SYNC_DIV1;
/* Set the SYNCSRC[1:0] bits according to CRS_Source value */
RCC_CRSInitStruct.Source = RCC_CRS_SYNC_SOURCE_USB;
/* HSI48 is synchronized with USB SOF at 1KHz rate */
RCC_CRSInitStruct.ReloadValue = __HAL_RCC_CRS_RELOADVALUE_CALCULATE(48000000, 1000);
RCC_CRSInitStruct.ErrorLimitValue = RCC_CRS_ERRORLIMIT_DEFAULT;
/* Set the TRIM[5:0] to the default value*/
RCC_CRSInitStruct.HSI48CalibrationValue = 0x20;
/* Start automatic synchronization */
HAL_RCCEx_CRSConfig (&RCC_CRSInitStruct);
}
/**
* @brief Main program
* @param None
* @retval None
*/
int main(void)
{
/* STM32F0xx HAL library initialization:
- Configure the Flash prefetch
- 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
*/
RCC_CRSSynchroInfoTypeDef syncinfo = {0};
HAL_Init();
/* Configure LED1, LED2, LED4 and LED3 */
BSP_LED_Init(LED1);
BSP_LED_Init(LED2);
BSP_LED_Init(LED4);
BSP_LED_Init(LED3);
/* Enable HSE oscillator and configure the PLL to reach the max system frequency (48 MHz)
when using HSE oscillator as PLL clock source. */
SystemClock_Config();
/* CRS initialization (enable HSI48 and LSE oscillators and then enable CRS clock */
/* Enable RCC_CRS interuption*/
CRS_Init();
/* HSI48 Synchronization without synchronization frequency (source set to GPIO */
/* which is not configured)*/
CRSInitStruct.Prescaler = RCC_CRS_SYNC_DIV1;
CRSInitStruct.Source = RCC_CRS_SYNC_SOURCE_GPIO;
CRSInitStruct.Polarity = RCC_CRS_SYNC_POLARITY_FALLING;
/* F(LSE)=32.768kHz then Reload=(f(Target)/f(LSE))-1= 0x5B7*/
CRSInitStruct.ReloadValue = __HAL_RCC_CRS_RELOADVALUE_CALCULATE(48000000,32768);
CRSInitStruct.ErrorLimitValue = RCC_CRS_ERRORLIMIT_DEFAULT;
/* Change the HSI trimming value to see the automatic calibration performed by CRS */
CRSInitStruct.HSI48CalibrationValue = 0x00;
/* Start automatic synchronization*/
HAL_RCCEx_CRSConfig(&CRSInitStruct);
/* Enable RCC_CRS Interuptions */
__HAL_RCC_CRS_ENABLE_IT(RCC_CRS_IT_SYNCOK | RCC_CRS_IT_SYNCWARN | RCC_CRS_IT_ERR | RCC_CRS_IT_ESYNC);
/* Simulate a SYNC EVENT which will raise a SYNC_MISS EVENT */
HAL_RCCEx_CRSSoftwareSynchronizationGenerate();
/* Infinite loop */
while (1)
{
/* Perform a new configuration to LSE when SYNC MISS is detected. */
if (CRSSyncStatus == 2)
{
/* Delay to see the LED power on switch from LED4 to LED1 */
HAL_Delay(1000);
/* Retrieve synchronization information if needed */
HAL_RCCEx_CRSGetSynchronizationInfo(&syncinfo);
/* Change source to LSE and restart synchronization */
CRSInitStruct.Source = RCC_CRS_SYNC_SOURCE_LSE;
HAL_RCCEx_CRSConfig(&CRSInitStruct);
/* Enable RCC_CRS Interuptions */
__HAL_RCC_CRS_ENABLE_IT(RCC_CRS_IT_SYNCOK | RCC_CRS_IT_SYNCWARN | RCC_CRS_IT_ERR | RCC_CRS_IT_ESYNC);
}
}
}
