Trying to set the STM32c031 clock to 48MHz. Target is not responding, retrying...

[houseman]

I have a STM32C031C6 and I’m trying to set the clock to be 48MHz

 

It works when I have the for loops in there, but its not supposed to have them and I want to get it working properly without needing them.

If I comment out 1 of the for loops, then after that it gives me this error 

I’m not sure what I am doing wrong, I think I’m not waiting properly for something, but I don’t know what that is.

Error in executing 'cont' command ...

Target is not responding, retrying...

Target is not responding, retrying...

Shutting down...

Target is not responding, retrying…

 

This is the code.

#include "stm32c031xx.h"

void speed_up_to_48mhz(void){


        //	1. ENABLE HSI and wait for the HSI to become Ready
        RCC->CR |= (1U << 8);

        while (!(RCC->CR & (1U << 10)));


        for(volatile int i =0; i<1000000; i++){}


        //bit 8 is prefetch 
        //bit 9 is instruction cache 


//1 wait state
        FLASH->ACR =  (1U << 9) | (1U << 0);

        FLASH->ACR &=~ (1U << 8);

        volatile uint32_t acr = FLASH->ACR;



        //ahb prescalar
        RCC->CFGR &=~ (1U << 11);
        RCC->CFGR &=~ (1U << 10);
        RCC->CFGR &=~ (1U << 9);
        RCC->CFGR &=~ (1U << 8);


        //apb prescalar

        RCC->CFGR &=~ (1U << 14);
        RCC->CFGR &=~ (1U << 13);
        RCC->CFGR &=~ (1U << 12);


    RCC->CR &=~ (1U<<11);
    RCC->CR &=~ (1U<<12);
    RCC->CR &=~ (1U<<13);


            while (!(RCC->CR & (1U<<10)));



    for(volatile int i =0; i<1000000; i++){}



}

 

[Carlo Ramirez]

I’d check the clock source and PLL configuration first, especially the ready/status flags and the order in which you switch SYSCLK. The delay loops may be masking a timing or synchronization issue rather than actually fixing it. Also, make sure the FLASH wait-state configuration is applied before increasing the CPU clock. The exact point where execution stops would help narrow it down.

[houseman]

thanks, I needed to apply the flash wait state before increasing the clock.

 

 

[Nathri]

Your clock source switch is missing. You enable HSI but never tell the MCU to actually use it.

After your FLASH ACR config, add:

********

RCC->CFGR = (RCC->CFGR & ~(0b11 << 0)) | (0b01 << 0);

while ((RCC->CFGR & (0b11 << 2)) != (0b01 << 2));

********

The SWS bits confirm the switch is done.

[houseman]

thanks, I needed to apply the flash wait state before increasing the clock.