Question
What is the correct systemClock_Config to use in order to have USB OTG FS with a 48MHz external cristal as the clock source ?
Hi,
I am working with a STM32H743 and I am trying to use USB OTG FS with the best clock configuration possible. I would like to have a SYSCLK at 480MHz and use the USB OTG FS with the external clock source HSE at 48MHz.
The frequency of the external cristal is 48MHz.
Currently, i have the USB working while using the internal 48MHz clock HSI48 and the SYSCLK at 64MHz using HSI.
Howerver it seem that the moment I switch either the SYSCLK or the USB OTG FS source frequency problems appears.
- If i choose to use the external clock as the source clock for the USB, my device isn't recognized by the computer at all.
- If i choose to use the external clock as the source clock for the SYSCLK, my device is recognized by the computer but is unable to start.
Either way, if i use the external clock, it doesn't seem to work.
Am I forgetting something in the systemClock_Config ?
Exemple of systemClock_Config with the external clock as the source clock for the SYSCLK :
RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE0);
while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI48|RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.HSIState = RCC_HSI_DIV1;
RCC_OscInitStruct.HSI48State = RCC_HSI48_ON;
RCC_OscInitStruct.CSIState = RCC_CSI_OFF;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = 5;
RCC_OscInitStruct.PLL.PLLN = 100;
RCC_OscInitStruct.PLL.PLLP = 2;
RCC_OscInitStruct.PLL.PLLQ = 10;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_3;
RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
RCC_OscInitStruct.PLL.PLLFRACN = 0;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB buses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2|RCC_CLOCKTYPE_D3PCLK1|RCC_CLOCKTYPE_D1PCLK1;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV2;
RCC_ClkInitStruct.APB3CLKDivider = RCC_APB3_DIV2;
RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV2;
RCC_ClkInitStruct.APB2CLKDivider = RCC_APB2_DIV2;
RCC_ClkInitStruct.APB4CLKDivider = RCC_APB4_DIV2;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
{
Error_Handler();
}
PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_SPI6|RCC_PERIPHCLK_SPI123|RCC_PERIPHCLK_I2C1|RCC_PERIPHCLK_USB;
PeriphClkInitStruct.PLL2.PLL2M = 32;
PeriphClkInitStruct.PLL2.PLL2N = 128;
PeriphClkInitStruct.PLL2.PLL2P = 3;
PeriphClkInitStruct.PLL2.PLL2Q = 3;
PeriphClkInitStruct.PLL2.PLL2R = 2;
PeriphClkInitStruct.PLL2.PLL2RGE = RCC_PLL2VCIRANGE_0;
PeriphClkInitStruct.PLL2.PLL2VCOSEL = RCC_PLL2VCOWIDE;
PeriphClkInitStruct.PLL2.PLL2FRACN = 0;
PeriphClkInitStruct.Spi123ClockSelection = RCC_SPI123CLKSOURCE_PLL2;
PeriphClkInitStruct.Spi6ClockSelection = RCC_SPI6CLKSOURCE_PLL2;
PeriphClkInitStruct.UsbClockSelection = RCC_USBCLKSOURCE_HSI48;
PeriphClkInitStruct.I2c123ClockSelection = RCC_I2C123CLKSOURCE_HSI;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
{
Error_Handler();
}