STM32F103C8T6 Bluepill giving Windows "Device Descriptor Request Failed"

Question

Hi all,Total newbie here.I am seeing this error in Windows 11 Device Manager: "Device Descriptor Request Failed", when I plug the Bluepill to a PC using Bluepill's onboard micro-USB PortAlthough the Bluepill looks like it is running OK with the previously flashed program (Blink PC13) with power supplied via the Bluepill's onboard micro-USB, Windows is giving this error. Being a "perferctionist", I would like to see the Windows error eliminated.I have check few "solutions" on youtube and none of them seems to apply to STM32, and thus not working. Can any kindly soul please help. Sorry if this has been asked before, but being a newbie to this site, I can't find anything suitable.

Thomas8 · Accepted Answer

How do you know his blue pill has a fake chip soldered? There are lot of BP boards with chips from other manufacturer. Moreover this error also happens with a original chip. Thats because ST simply forgot to integrate a switchable 1k5 connect resistor. So the BP adds a 1K5 resistor from PA12 to V3.3.

The downside of this is the host sees a new connected USB device and tries to enumerate it. This of course fails when no usb firmware is loaded.

There are 2 possible solutions:

1. use a usb cable with VBUS and GND only so there are no D+ and D- connection. (Charge only cable) to power the BluePill board.

2. set PA12 to output and PA12 to low so the host cant see the 1k5 resistor

 // Pin PA12 as Open Drain Output 
 GPIOA->CRH &= ~(0b1111 << 16);
 GPIOA->CRH |= (0b0110 << 16);
 // set PA12 low
 GPIOA->ODR &= ~(1 << 12);

dont forget to set PA12 back to floading input before you want to use USB.

 GPIOA->CRH &= ~(0b1111 << 16);

thats all

Peter BENSCH · Answer

Welcome @JLHK01, to the community!If you use the search function of the community and search for ‘blue pill’, you will find a lot of similar questions. You will also very often find answers such as: ‘blue pill is not a product of STMicroelectronics and has only been using counterfeit STM32F103 for years’. This means that you should ask the manufacturer of the blue pill or the counterfeit, not the manufacturer of the original STM32F103.You can also convert the Blue Pill: simply unsolder the counterfeit and fit an original STM32F103C8T6 - you are immediately compatible and you will be gladly helped here.Good luck!/Peter

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