Foreword
Looking at knowledge routine STM32H743I-EVAL2 board. Counted, it seems to have more than 100 demo.
Now look RCC_ClockConfig routine. Which used an external interrupt demo of knowledge.
RCC_ClockConfig routine, external interrupt (button) in response to dynamically switching the clock source to the HSE, HSI, CSI.
Knowledge point of view to understand, but I do not know the scenario of this demo. There is no use CubeMx reconstruction works, just look at it, know of it.
So what demand will dynamically switch clock source it? Clock source is generally used with a good CubeMX generate initialization code is not changed.
. Routine by generating CubeMx SystemClock_Config (), called at the main function
of dynamically switching the clock source function: SystemClockCSI_Config (), SystemClockHSI_Config () , SystemClockHSE_Config ().
These four functions make a note of.
test
External interrupt pressing, to modify the order of the HSE clock source (the HSE clock source is initialized), press the button, the response function to dynamically modify the order of the external clock source interrupt HSE => HSI => CSI => HSE
/**
* @brief switch in system clock out of ISR context.
* @retval None
*/
static void SwitchSystemClock(void)
{
if (__HAL_RCC_GET_PLL_OSCSOURCE() == RCC_PLLSOURCE_HSI)
{
// 2. HSI => CSI
/* PLL source is HSI oscillator */
/* Set SYSCLK frequency to 400000000 Hz, coming from the PLL which is clocked by CSI */
SystemClockCSI_Config();
}
else if (__HAL_RCC_GET_PLL_OSCSOURCE() == RCC_PLLSOURCE_HSE)
{
// CubeMx配置的时钟源是HSE, 所以按下按键后，先执行的是这里 1. HSE => HSI
/* PLL source is HSE oscillator */
/* Set SYSCLK frequency to 400000000 Hz, coming from the PLL which is clocked by HSI */
SystemClockHSI_Config();
}
else if (__HAL_RCC_GET_PLL_OSCSOURCE() == RCC_PLLSOURCE_CSI)
{
/* PLL source is CSI oscillator */
/* Set SYSCLK frequency to 400000000 Hz, coming from the PLL which is clocked by HSE */
// 3. CSI => HSE 回到系统默认时钟源
SystemClockHSE_Config();
}
/* reset global variable */
SwitchClock = RESET;
}
Initialization clock source
/**
* @brief System Clock Configuration
* The system Clock is configured as follow :
* System Clock source = PLL (HSE)
* SYSCLK(Hz) = 400000000 (CPU Clock)
* HCLK(Hz) = 200000000 (AXI and AHBs Clock)
* AHB Prescaler = 2
* D1 APB3 Prescaler = 2 (APB3 Clock 100MHz)
* D2 APB1 Prescaler = 2 (APB1 Clock 100MHz)
* D2 APB2 Prescaler = 2 (APB2 Clock 100MHz)
* D3 APB4 Prescaler = 2 (APB4 Clock 100MHz)
* HSE Frequency(Hz) = 25000000
* PLL_M = 5
* PLL_N = 160
* PLL_P = 2
* PLL_Q = 4
* PLL_R = 2
* VDD(V) = 3.3
* Flash Latency(WS) = 4
* @param None
* @retval None
*/
static void SystemClock_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_OscInitTypeDef RCC_OscInitStruct;
/*!< Supply configuration update enable */
HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);
/* 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_SCALE1);
while ((PWR->D3CR & (PWR_D3CR_VOSRDY)) != PWR_D3CR_VOSRDY) {}
/* Enable HSE Oscillator and activate PLL with HSE as source */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE; // 默认是使用HSE晶振
// 只打开HSE, 关掉(HSI, CSI)
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.HSIState = RCC_HSI_OFF;
RCC_OscInitStruct.CSIState = RCC_CSI_OFF;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON; // 使用锁相环
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE; // 锁相环的源是HSE
// 锁相环参数可以打开CubeMx看一下
RCC_OscInitStruct.PLL.PLLM = 5;
RCC_OscInitStruct.PLL.PLLN = 160;
RCC_OscInitStruct.PLL.PLLFRACN = 0;
RCC_OscInitStruct.PLL.PLLP = 2;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLQ = 4;
RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
while(1) {}
}
// 设置外设通道时钟(指定经过PLL后的分频系数)
/* Select PLL as system clock source and configure bus clocks dividers */
RCC_ClkInitStruct.ClockType = (
RCC_CLOCKTYPE_SYSCLK
| RCC_CLOCKTYPE_HCLK
| RCC_CLOCKTYPE_D1PCLK1
| RCC_CLOCKTYPE_PCLK1
| RCC_CLOCKTYPE_PCLK2
| RCC_CLOCKTYPE_D3PCLK1);
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;
// 设置是外设时钟通道
// FLASH_LATENCY_4 为闪存延迟要4个时钟周期
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
{
while(1) {}
}
}
Switch the clock source from CSI => HSE
/**
* @brief Switch the PLL source from CSI to HSE , and select the PLL as SYSCLK
* The system Clock is configured as follow :
* System Clock source = PLL (HSE)
* SYSCLK(Hz) = 400000000 (CPU Clock)
* HCLK(Hz) = 200000000 (AXI and AHBs Clock)
* AHB Prescaler = 2
* D1 APB3 Prescaler = 2 (APB3 Clock 100MHz)
* D2 APB1 Prescaler = 2 (APB1 Clock 100MHz)
* D2 APB2 Prescaler = 2 (APB2 Clock 100MHz)
* D3 APB4 Prescaler = 2 (APB4 Clock 100MHz)
* HSE Frequency(Hz) = 25000000
* PLL_M = 5
* PLL_N = 160
* PLL_P = 2
* PLL_Q = 4
* PLL_R = 2
* VDD(V) = 3.3
* Flash Latency(WS) = 4
* @param None
* @retval None
*/
static void SystemClockHSE_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
// 现将时钟源切到CSI上, 才能修改时钟源(这是和第一次初始化时钟不一样的地方)
/* -1- Select CSI as system clock source to allow modification of the PLL configuration */
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_CSI;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/* -2- Enable HSE Oscillator, select it as PLL source and finally activate the PLL */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE; // 操作的时钟源为HSE
RCC_OscInitStruct.HSEState = RCC_HSE_ON; // HSE开
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON; // PLL开
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE; // PLL源为HSE
// 参照CubeMX图形化配置
RCC_OscInitStruct.PLL.PLLM = 5;
RCC_OscInitStruct.PLL.PLLN = 160;
RCC_OscInitStruct.PLL.PLLFRACN = 0;
RCC_OscInitStruct.PLL.PLLP = 2;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLQ = 4;
RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
// 设置设备通道时钟
/* Select PLL as system clock source and configure bus clocks clocks dividers */
RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK
| RCC_CLOCKTYPE_HCLK
| RCC_CLOCKTYPE_D1PCLK1
| RCC_CLOCKTYPE_PCLK1
| RCC_CLOCKTYPE_PCLK2
| RCC_CLOCKTYPE_D3PCLK1);
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)
{
/* Initialization Error */
Error_Handler();
}
// 只开HSE（关掉CSI, 因为上一个时钟源是CSI）
/* -4- Optional: Disable CSI Oscillator (if the HSI is no more needed by the application)*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_CSI; // 操作的时钟源为CSI
RCC_OscInitStruct.CSIState = RCC_CSI_OFF; // 关掉CSI
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE; // 断开CSI和PLL的连接
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
}
/**
* @brief Switch the PLL source from HSE to HSI, and select the PLL as SYSCLK
* source.
* System Clock source = PLL (HSI)
* SYSCLK(Hz) = 400000000 (CPU Clock)
* HCLK(Hz) = 200000000 (AXI and AHBs Clock)
* AHB Prescaler = 2
* D1 APB3 Prescaler = 2 (APB3 Clock 100MHz)
* D2 APB1 Prescaler = 2 (APB1 Clock 100MHz)
* D2 APB2 Prescaler = 2 (APB2 Clock 100MHz)
* D3 APB4 Prescaler = 2 (APB4 Clock 100MHz)
* HSI Frequency(Hz) = 64000000
* PLL_M = 16
* PLL_N = 200
* PLL_P = 2
* PLL_Q = 4
* PLL_R = 2
* VDD(V) = 3.3
* Flash Latency(WS) = 4
* @param None
* @retval None
*/
static void SystemClockHSI_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
// 先指定一个和要修改的目标时钟源不同的时钟源，才能修改目标时钟源
// e.g. 要修改HSI为最终要用的时钟源，那先将时钟源设定为空闲的时钟源(e.g. 现在的时钟源为HSE, 要修改时钟源为HSI)
/* -1- Select HSE as system clock source to allow modification of the PLL configuration */
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSE;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/* -2- Enable HSI Oscillator, select it as PLL source and finally activate the PLL */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
// 参照CubeMx图形化设置
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLM = 16;
RCC_OscInitStruct.PLL.PLLN = 200;
RCC_OscInitStruct.PLL.PLLFRACN = 0;
RCC_OscInitStruct.PLL.PLLP = 2;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLQ = 4;
RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/* Select PLL as system clock source and configure bus clocks clocks dividers */
// 设置设备时钟通道
RCC_ClkInitStruct.ClockType = (
RCC_CLOCKTYPE_SYSCLK
| RCC_CLOCKTYPE_HCLK
| RCC_CLOCKTYPE_D1PCLK1
| RCC_CLOCKTYPE_PCLK1
| RCC_CLOCKTYPE_PCLK2
| RCC_CLOCKTYPE_D3PCLK1);
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)
{
/* Initialization Error */
Error_Handler();
}
/* -4- Optional: Disable HSE Oscillator (if the HSE is no more needed by the application) */
// 关掉以前的时钟源(HSE).
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_OFF;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
}
/**
* @brief Switch the PLL source from HSI to CSI, and select the PLL as SYSCLK
* source.
* System Clock source = PLL (CSI)
* SYSCLK(Hz) = 400000000 (CPU Clock)
* HCLK(Hz) = 200000000 (AXI and AHBs Clock)
* AHB Prescaler = 2
* D1 APB3 Prescaler = 2 (APB3 Clock 100MHz)
* D2 APB1 Prescaler = 2 (APB1 Clock 100MHz)
* D2 APB2 Prescaler = 2 (APB2 Clock 100MHz)
* D3 APB4 Prescaler = 2 (APB4 Clock 100MHz)
* CSI Frequency(Hz) = 4000000
* PLL_M = 1
* PLL_N = 200
* PLL_P = 2
* PLL_Q = 4
* PLL_R = 2
* VDD(V) = 3.3
* Flash Latency(WS) = 4
* @param None
* @retval None
*/
static void SystemClockCSI_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
// 因为上一个时钟源是HSI(按钮按下的时钟源切换顺序为 HSE => HSI => CSI => HSE), 所以要先切到HSI
/* -1- Select HSI as system clock source to allow modification of the PLL configuration */
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/* -2- Enable CSI Oscillator, select it as PLL source and finally activate the PLL */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_CSI;
RCC_OscInitStruct.CSIState = RCC_CSI_ON;
RCC_OscInitStruct.CSICalibrationValue = RCC_CSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_CSI;
RCC_OscInitStruct.PLL.PLLM = 1;
RCC_OscInitStruct.PLL.PLLN = 200;
RCC_OscInitStruct.PLL.PLLFRACN = 0;
RCC_OscInitStruct.PLL.PLLP = 2;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLQ = 4;
RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/* Select PLL as system clock source and configure bus clocks clocks dividers */
RCC_ClkInitStruct.ClockType = (
RCC_CLOCKTYPE_SYSCLK
| RCC_CLOCKTYPE_HCLK
| RCC_CLOCKTYPE_D1PCLK1
| RCC_CLOCKTYPE_PCLK1
| RCC_CLOCKTYPE_PCLK2
| RCC_CLOCKTYPE_D3PCLK1);
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)
{
/* Initialization Error */
Error_Handler();
}
/* -4- Optional: Disable HSI Oscillator (if the HSI is no more needed by the application) */
// 关掉上一个时钟源HSI
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSEState = RCC_HSI_OFF;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
}
to sum up
This demo has little significance.
Without the aid of CubeMx, how to write clock initialization? Those frequency, the multiplication factor (less complex coefficient ...) how to fill?
The actual project board, clock sources are used in HSE crystal on external (for clock accuracy), then why should cut to the on-chip oscillator do?
If an external crystal is broken, as if to say on the document, STMCU automatically cut to the HSI (to maintain the system does not hang up, but the operating speed will be greatly reduced). Why would we cut it by hand to the on-chip oscillator do?
