Change STM32F103 Frequency at run time

[pkumar1883]

Posted on February 17, 2017 at 06:28

Hi,

I am using STM32F103. I have configured my clock at 72 MHz as shown in the below code--

RCC_DeInit(); msDelay(10); RCC_HSEConfig(RCC_HSE_OFF); msDelay(10); RCC_HSEConfig(RCC_HSE_ON); while(1){ HSEStartUpStatus = RCC_WaitForHSEStartUp(); if(HSEStartUpStatus == SUCCESS) break; } if(HSEStartUpStatus == SUCCESS) { RCC_PLLCmd(DISABLE); RCC_HCLKConfig(RCC_SYSCLK_Div1); RCC_PCLK2Config(RCC_HCLK_Div1); RCC_PCLK1Config(RCC_HCLK_Div2); FLASH_SetLatency(FLASH_Latency_2); FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable); if(HSE_VALUE==16000000){ RCC_PLLConfig(RCC_PLLSource_HSE_Div2,RCC_PLLMul_9); } else{ RCC_PLLConfig(RCC_PLLSource_HSE_Div1,RCC_PLLMul_9); } RCC_PLLCmd(ENABLE); while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET){} RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK); while(RCC_GetSYSCLKSource() != 0x08){} Flag_SYS_SPEED_72=SET; Flag_HSE_Active=SET; } else { RCC_HSIConfiguration(); Flag_HSI_Active=SET; }

Now I want to reconfigure my system clock at run time. I want to run my system at 8MHz. Please suggest how to do this.

[pkumar1883]

Posted on February 17, 2017 at 06:34

Please see my code is as below-

     RCC_DeInit();

        msDelay(10);        RCC_HSEConfig(RCC_HSE_OFF);        msDelay(10);        RCC_HSEConfig(RCC_HSE_ON);              while(1){                  HSEStartUpStatus = RCC_WaitForHSEStartUp();                  if(HSEStartUpStatus == SUCCESS)                      break;              }            if(HSEStartUpStatus == SUCCESS)            {                RCC_PLLCmd(DISABLE);                RCC_HCLKConfig(RCC_SYSCLK_Div1);                RCC_PCLK2Config(RCC_HCLK_Div1);                RCC_PCLK1Config(RCC_HCLK_Div2);                FLASH_SetLatency(FLASH_Latency_2);                FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);                if(HSE_VALUE==16000000){                    RCC_PLLConfig(RCC_PLLSource_HSE_Div2,RCC_PLLMul_9);                }                else{                    RCC_PLLConfig(RCC_PLLSource_HSE_Div1,RCC_PLLMul_9);                }                RCC_PLLCmd(ENABLE);                while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET){}                RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);                while(RCC_GetSYSCLKSource() != 0x08){}                Flag_SYS_SPEED_72=SET;                Flag_HSE_Active=SET;

            }

            else {                RCC_HSIConfiguration();                Flag_HSI_Active=SET;            }