CODEWITHSUNDEEP
stm32system-clockstm32ldiscovery
Chethan Singh
Chethan Singh

Reputation: 11

My code gets stuck in while loop at comment number 7 when waiting for status to to select the system clock as PLL clock?

#define TIMEOUT 1000000  // Timeout value to avoid infinite loops
/* System Clock Configuration */
void cfg_sys_clock()
{
        uint32_t timeout;

        //select 8khz as MSI
        MODIFY_REG(RCC->CR, RCC_CR_MSIRANGE, _VAL2FLD(RCC_CR_MSIRANGE, 0x7)); 

        // 1. Enable MSI
        SET_BIT(RCC->CR, RCC_CR_MSION);

        // 2. Wait for HSI Ready
        timeout = TIMEOUT;
        while (!(READ_BIT(RCC->CR, RCC_CR_MSIRDY)) && --timeout);
        if (timeout == 0) while (1); // Hang in case of failure

        // 3. Configure PLL
        MODIFY_REG(RCC->PLLCFGR,
            RCC_PLLCFGR_PLLSRC | RCC_PLLCFGR_PLLM | RCC_PLLCFGR_PLLN |RCC_PLLCFGR_PLLR,
        RCC_PLLCFGR_PLLSRC_MSI | _VAL2FLD(RCC_PLLCFGR_PLLM, 1) |
        _VAL2FLD(RCC_PLLCFGR_PLLN, 24) | _VAL2FLD(RCC_PLLCFGR_PLLR, 2)
        );

        // 4. Enable PLL
        SET_BIT(RCC->CR, RCC_CR_PLLON);

        // 5. Wait for PLL Ready
        timeout = TIMEOUT;
        while (!(READ_BIT(RCC->CR, RCC_CR_PLLRDY)) && --timeout);
        if (timeout == 0) while (1); // Hang in case of failure

        // 6. Set PLL as system clock
        MODIFY_REG(RCC->CFGR, RCC_CFGR_SW, RCC_CFGR_SW_PLL);

        // 7. Wait until PLL is used as system clock
        timeout = TIMEOUT;
        while ((READ_BIT(RCC->CFGR, RCC_CFGR_SWS) != RCC_CFGR_SWS_PLL) && --timeout);
        if(timeout == 0) while (1); // Hang in case of failure

        // 8. Set AHB and APB prescalers (No division)
        MODIFY_REG(RCC->CFGR, RCC_CFGR_HPRE, RCC_CFGR_HPRE_DIV1);
        MODIFY_REG(RCC->CFGR, RCC_CFGR_PPRE1, RCC_CFGR_PPRE1_DIV1); 
        MODIFY_REG(RCC->CFGR, RCC_CFGR_PPRE2, RCC_CFGR_PPRE2_DIV1); 
}

flash latency is correctly set to 4ws , and board using is B-L4S5I-IOT01A stm32 controller - STM32L4S5VIT6, My code gets stuck in while loop at comment number 7 when waiting for status to to select the system clock as PLL clock ?

Upvotes: 1

Views: 50

Answers (1)

wek
wek

Reputation: 1213

Always start debugging with reading out content of relevant registers (here besides RCC also the register setting FLASH waitstates) and checking their content.

My guess is, that you don't have RCC_PLLCFGR.PLLREN set.

Upvotes: 0

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