cancel
Showing results for 
Search instead for 
Did you mean: 

STM32F407VET PLL problem

kareemkna
Associate II
Posted on July 07, 2015 at 17:00

I used STM32 cube for the PLL configuration

// Enable HSE Oscillator and activate PLL with HSE as source
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
// This assumes the HSE_VALUE is a multiple of 1MHz. If this is not
// your case, you have to recompute these PLL constants.
RCC_OscInitStruct.PLL.PLLM = (HSE_VALUE/1000000u);
RCC_OscInitStruct.PLL.PLLN = 336;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 7;
HAL_RCC_OscConfig(&RCC_OscInitStruct);
// 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;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5);
And used this function to get the system clock
Sys_Freq=HAL_RCC_GetSysClockFreq();
Sys_Freq after calling this function = 168, so the initialization is correct

used this function to rout system clock on MCO1,,, the GPIO also made with STM32Cube
HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_PLLCLK, RCC_MCODIV_2);

the logic analyser shows only 9 Mhz on MCO1 where it should be 84Mhz.. So my Question is, WHAT I AM MISSING ??????

I would very much appreciate any help or suggestion, its been 3 days and didnt have any luck solving this problem :(

11 REPLIES 11
kareemkna
Associate II
Posted on July 07, 2015 at 18:36

done,,, it shows 9.6 Mhz o.O ::    The scope is 500Mhz

Posted on July 07, 2015 at 18:49

If you've been doing this for 3 days, you should probably go talk through the issues and design with a more senior member of staff.

You should probably start looking at other aspects of your design, the supplies, and the voltages, capacitors, on the VCAPx pins.

Tips, Buy me a coffee, or three.. PayPal Venmo
Up vote any posts that you find helpful, it shows what's working..