mbed-os/targets/TARGET_STM/TARGET_STM32F4/TARGET_STM32F401xE/system_clock.c

/* mbed Microcontroller Library
 * SPDX-License-Identifier: BSD-3-Clause
 ******************************************************************************
 *
 * Copyright (c) 2015-2021 STMicroelectronics.
 * All rights reserved.
 *
 * 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
 *
 ******************************************************************************
 */

/**
  * This file configures the system clock as follows:
  *-----------------------------------------------------------------------------
  * System clock source | 1- USE_PLL_HSE_EXTC (external 8 MHz clock)
  *                     | 2- USE_PLL_HSE_XTAL (external 8 MHz xtal)
  *                     | 3- USE_PLL_HSI (internal 16 MHz)
  *-----------------------------------------------------------------------------
  * SYSCLK(MHz)         | 84
  * AHBCLK (MHz)        | 84
  * APB1CLK (MHz)       | 42
  * APB2CLK (MHz)       | 84
  * USB capable         | YES
  *-----------------------------------------------------------------------------
**/

#include "stm32f4xx.h"
#include "mbed_error.h"

// clock source is selected with CLOCK_SOURCE in json config
#define USE_PLL_HSE_EXTC     0x8  // Use external clock (ST Link MCO)
#define USE_PLL_HSE_XTAL     0x4  // Use external xtal (X3 on board - not provided by default)
#define USE_PLL_HSI          0x2  // Use HSI internal clock


#if ( ((CLOCK_SOURCE) & USE_PLL_HSE_XTAL) || ((CLOCK_SOURCE) & USE_PLL_HSE_EXTC) )
uint8_t SetSysClock_PLL_HSE(uint8_t bypass);
#endif /* ((CLOCK_SOURCE) & USE_PLL_HSE_XTAL) || ((CLOCK_SOURCE) & USE_PLL_HSE_EXTC) */

#if ((CLOCK_SOURCE) & USE_PLL_HSI)
uint8_t SetSysClock_PLL_HSI(void);
#endif /* ((CLOCK_SOURCE) & USE_PLL_HSI) */


/*
 * @brief  Configures the System clock source, PLL Multiplier and Divider factors,
 *               AHB/APBx prescalers and Flash settings
 * @note   This function should be called only once the RCC clock configuration
 *         is reset to the default reset state (done in SystemInit() function).
 * @param  None
 * @retval None
 */

MBED_WEAK void SetSysClock(void)
{
#if ((CLOCK_SOURCE) & USE_PLL_HSE_EXTC)
    /* 1- Try to start with HSE and external clock */
    if (SetSysClock_PLL_HSE(1) == 0)
#endif
    {
#if ((CLOCK_SOURCE) & USE_PLL_HSE_XTAL)
        /* 2- If fail try to start with HSE and external xtal */
        if (SetSysClock_PLL_HSE(0) == 0)
#endif
        {
#if ((CLOCK_SOURCE) & USE_PLL_HSI)
            /* 3- If fail start with HSI clock */
            if (SetSysClock_PLL_HSI() == 0)
#endif
            {
                {
                    error("SetSysClock failed\n");
                }
            }
        }
    }

    /* Output clock on MCO2 pin(PC9) for debugging purpose */
    //HAL_RCC_MCOConfig(RCC_MCO2, RCC_MCO2SOURCE_SYSCLK, RCC_MCODIV_4);
}

#if ( ((CLOCK_SOURCE) & USE_PLL_HSE_XTAL) || ((CLOCK_SOURCE) & USE_PLL_HSE_EXTC) )
/******************************************************************************/
/*            PLL (clocked by HSE) used as System clock source                */
/******************************************************************************/
MBED_WEAK uint8_t SetSysClock_PLL_HSE(uint8_t bypass)
{
    RCC_OscInitTypeDef RCC_OscInitStruct;
    RCC_ClkInitTypeDef RCC_ClkInitStruct;

    /* 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_RCC_PWR_CLK_ENABLE();
    __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE2);

    /* Get the Clocks configuration according to the internal RCC registers */
    HAL_RCC_GetOscConfig(&RCC_OscInitStruct);

    /* PLL could be already configured by bootlader */
    if (RCC_OscInitStruct.PLL.PLLState != RCC_PLL_ON) {

        // Enable HSE oscillator and activate PLL with HSE as source
        RCC_OscInitStruct.OscillatorType      = RCC_OSCILLATORTYPE_HSE;
        if (bypass == 0) {
            RCC_OscInitStruct.HSEState          = RCC_HSE_ON; // External 8 MHz xtal on OSC_IN/OSC_OUT
        } else {
            RCC_OscInitStruct.HSEState          = RCC_HSE_BYPASS; // External 8 MHz clock on OSC_IN
        }

        RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
        RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
        RCC_OscInitStruct.PLL.PLLM            = 8;             // VCO input clock = 1 MHz (8 MHz / 8)
        RCC_OscInitStruct.PLL.PLLN            = 336;           // VCO output clock = 336 MHz (1 MHz * 336)
        RCC_OscInitStruct.PLL.PLLP            = RCC_PLLP_DIV4; // PLLCLK = 84 MHz (336 MHz / 4)
        RCC_OscInitStruct.PLL.PLLQ            = 7;             // USB clock = 48 MHz (336 MHz / 7) --> OK for USB
        if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
            return 0; // FAIL
        }
    }

    // Select PLL 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_PLLCLK; // 84 MHz
    RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;         // 84 MHz
    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;           // 42 MHz
    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;           // 84 MHz
    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK) {
        return 0; // FAIL
    }

    /* Output clock on MCO1 pin(PA8) for debugging purpose */
    /*
    if (bypass == 0)
      HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_HSE, RCC_MCODIV_2); // 4 MHz
    else
      HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_HSE, RCC_MCODIV_1); // 8 MHz
    */

    return 1; // OK
}
#endif /* ((CLOCK_SOURCE) & USE_PLL_HSE_XTAL) || ((CLOCK_SOURCE) & USE_PLL_HSE_EXTC) */

#if ((CLOCK_SOURCE) & USE_PLL_HSI)
/******************************************************************************/
/*            PLL (clocked by HSI) used as System clock source                */
/******************************************************************************/
uint8_t SetSysClock_PLL_HSI(void)
{
    RCC_OscInitTypeDef RCC_OscInitStruct;
    RCC_ClkInitTypeDef RCC_ClkInitStruct;

    /* 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_RCC_PWR_CLK_ENABLE();
    __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE2);

    // Enable HSI oscillator and activate PLL with HSI as source
    RCC_OscInitStruct.OscillatorType      = RCC_OSCILLATORTYPE_HSI | RCC_OSCILLATORTYPE_HSE;
    RCC_OscInitStruct.HSIState            = RCC_HSI_ON;
    RCC_OscInitStruct.HSEState            = RCC_HSE_OFF;
    RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
    RCC_OscInitStruct.PLL.PLLState        = RCC_PLL_ON;
    RCC_OscInitStruct.PLL.PLLSource       = RCC_PLLSOURCE_HSI;
    RCC_OscInitStruct.PLL.PLLM            = 16;            // VCO input clock = 1 MHz (16 MHz / 16)
    RCC_OscInitStruct.PLL.PLLN            = 336;           // VCO output clock = 336 MHz (1 MHz * 336)
    RCC_OscInitStruct.PLL.PLLP            = RCC_PLLP_DIV4; // PLLCLK = 84 MHz (336 MHz / 4)
    RCC_OscInitStruct.PLL.PLLQ            = 7;             // USB clock = 48 MHz (336 MHz / 7) --> freq is ok but not precise enough
    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
        return 0; // FAIL
    }

    /* Select PLL 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_PLLCLK; // 84 MHz
    RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;         // 84 MHz
    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;           // 42 MHz
    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;           // 84 MHz
    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK) {
        return 0; // FAIL
    }

    /* Output clock on MCO1 pin(PA8) for debugging purpose */
    //HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_HSI, RCC_MCODIV_1); // 16 MHz

    return 1; // OK
}
#endif /* ((CLOCK_SOURCE) & USE_PLL_HSI) */