device descriptor request failed with STM32F207VT(100pins) custom board, same code is working fine with STM32F207ZGT(144 pins) nucleo board

[Pranay Dhuri]

Posted on June 05, 2018 at 19:57

Hi there,

I have generated USB CDC code from cubeMX  for STM32F207ZT (144 pins) nulcleo board and it is working fine USB device is getting listed in COM ports. 

Now I am flashing the same code with some minor clock changes (as my custom board is having 25MHz crystal and DK having 8MHz crystal) pin configurations are same (pins are assigned correctly to support both packages).

following are the clock initialization done for custom board:

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 = 240; RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2; RCC_OscInitStruct.PLL.PLLQ = 5;

After flashing code USB device is not getting detected , instead it is showing Device description request failed. I have seen similar queries on forum but in my case code is already working fine with development board. The difference in DK and custom board is just pin package and crystal that we are using.

Thanks in advance.

[Tesla DeLorean]

Posted on June 05, 2018 at 20:15

You might want to check the stepping of the parts being used here.

Check voltages on VCAP pins, and capacitors.

Check the HSE for accuracy, stability, and time to start.

Check the PLL via PA8 (MCO).

Review, critically, the design, component, and layout differences between the working design and your design.