LwIP_HTTP_Server_Netconn_RTOS on STM32F767-Nucleo not compliant with RCC / PLL spec.

[Johi]

Hello,

I am using nucleo F767zi to run LwIP_HTTP_Server_Netconn_RTOS.

According to the MX configurator and according to DocID029041 Rev 6 (SM32F767xx Electrical characteristics) page 143 Fpll_should be [0,95-2,1Mhz].

The mentioned example generates (IMHO) .32 Mhz well outside the forementioned interval.

Details:

/* 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;
  RCC_OscInitStruct.PLL.PLLM = 25;
  RCC_OscInitStruct.PLL.PLLN = 400;  
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 9;
  RCC_OscInitStruct.PLL.PLLR = 7;
 
// so => Fpllin = 8 Mhz / M = 8 Mhz / 25 = 0,32

MX configurator comes to the same conclusion:

It is a bit strange that an ST example designed (?) for the 767zi board does not comply with the specs?

In the same line the example specifies: (main .c line 72)

/* Configure the system clock to 200 MHz */
SystemClock_Config();   

Whereas, according to the code fPllout = fpllin * 400/2 = 64Mhz.

Could it be that I am missing something, because it seems a bit odd (provided my analysis is correct) for ST to provide examples that are outside the specs?

My intention is to use the example as a starting point for my application, but therefore I would assume that the example is compliant with the board, but at first sight it seems not the case?

[Piranha · Accepted solution]

Obviously it's a copy-paste from the boards with a 25 MHz HSE clock, like this one. And there is another bug - both of these boards are using an external clock signal, not a crystal. Therefore for both of these the .PLL.PLLState must be set to RCC_HSE_BYPASS.

For unmodified NUCLEO-F767ZI board the best setting for the maximum speed is:

8 MHz / 4 * 216 / 2 = 216 MHz.

Just in case you don't know:

https://community.st.com/s/question/0D50X0000BOtfhnSQB/how-to-make-ethernet-and-lwip-working-on-stm32

@Imen DAHMEN​, and another way the examples are broken...

[MSG_ST]

Hi,

Thank you for your contribution.

Internal ticket number: 146455

(This is an internal tracking number and is not accessible or usable by customers).

Will be fixed in next F7 maintenance release.

Regards

Mahdy