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STM32F407 change to 25MHz usart3 baud rate problem

Question asked by Elliott Li on Oct 5, 2017
Latest reply on Oct 8, 2017 by Elliott Li

Hi all,

 

I am using STM32F407VET6 with 25MHz crystal by STM32Cube_FW_F4_V1.16. I have changed HSE_VALUE to 25000000 in system_stm32f4xx.c and RCC_OscInitStruct.PLL.PLLM = 25 in SystemClock_Config main.c, but I found that usart3 baud rate is not correct. I set the baud rate to 9600, but I got 30075 from Oscilloscope. The method I used is in http://www.st.com/content/ccc/resource/technical/document/application_note/group0/66/fa/62/a2/5c/75/48/a8/DM00327191/fil…  Page 9.

Here is my result.

 

Please help me. Thank you

 

Regards,

Elliott

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