STM32F405 doesn't want to enter DFU mode using USB typeC.

[Taras_Burko]

Congratulations. I have such a problem. I've made 1000 PCB prototypes and 30% don't want to enter DFU mode. If you try to turn the PCB back on multiple times, the part will go into DFU.I'm using a USB Type-C connector, could that be the problem? Also tried changing the USB cable, but that didn't fix the problem.I use a microcontroller STM32F405RGT6TR.

What can this be related to?

[STOne-32]

Dear @Taras_Burko ,

 

Here are my thoughts :

1) remove the two 22 Ohm serial resistances R14 and R16 and replace by a 0Ohm .

2) Can you show the HSE Crystal and reference . Try to put a crystal with 8MHz or 4MHz on the failing parts and let us know if it improve the behavior .

Hope it helps you .

STOne-32

[Taras_Burko]

I replaced the resistors with 0 ohms. HSE Crystal stands at 8 mhz.Nothing has changed. The microcontroller refuses to enter DFU.

You need to try to connect the USB cable 10-30 times, and then you can enter DFU mode. If I go into DFU and download the firmware the microcontroller works fine and always connects to the PC via USB and runs the PC program. But does not want to enter DFU mode using the button. I checked the button, it works fine. That is, there is a problem of entering DFU mode using the button.

[STOne-32]

Dear @Taras_Burko ,

It is indeed a strange behavior.  can you try this 

How to optimize STM32 MCUs internal RC oscillator accuracy  

Try to connect via SWD/JTAG and program a simple program , then measure the HSI frequency that should be at 16MHz - you can output on MCO pin and send us the waveforms.   

Thank you

STOne-32.

[Pavel A.]

Now please send pictures from good boards.

 

[Taras_Burko]

Here is the frequency
prototypes that go into DFU. 

[Taras_Burko]

..

[Taras_Burko]

Hi. How do I solve this problem? I tried different USB cables and connected to another PC, but nothing helped
((((

[Pavel A.]

Looks like you need a USB bus analyzer (real, not software) and somebody who knows how to use it.

On the other hand you have 70% of good boards. Consider other 30% as defects ((