Sometimes my STM32L152 device in DFU mode is not recognized by Windows 10 (64bits)

[Francois Fustin]

Posted on March 10, 2017 at 14:27

Hello everyone,

I am working on a project with a STM32L151 microcontroller.

I want to be able to upgrade its firmware via DFU mode.

The DFU driver is well installed, the device goes well in DFU mode when needed, I can well erase and download a new firmware to the device without problem with the DFUse demo program.

Except sometimes when DFU device is not recognized by Windows 10 and I don't know why.

With Beagle (USB hardware tracer) I can clearly see that device doesn't answer to the first SETUP packet sent by Windows.

But why this happens 1 times on 10 and how to avoid this problem?

Is somebody already had this problem? It could be interesting to have some clues to not have this annoying behavior.

[Nesrine M_O]

Posted on March 15, 2017 at 12:24

Hi

fustin.francois

,

this happens 1 times on 10

• is this sestimaticly happens afer 10 times,
• To be compliant with the USB 2.0 full speed electrical specification, the USB_DP (D+) pin should be pulled up with a 1.5 kΩ resistor to a 3.0-to-3.6 V voltage range.
• Please refer to

  http://www.st.com/content/ccc/resource/technical/document/application_note/b9/9b/16/3a/12/1e/40/0c/CD001675pdf/files/CD001675pdf/jcr:content/translations/en.CD001675pdf

  and

  http://www.st.com/content/ccc/resource/technical/document/application_note/6a/17/92/02/58/98/45/0c/CD00264pdf/files/CD00264pdf/jcr:content/translations/en.CD00264pdf

-Nesrine-

[Francois Fustin]

Posted on March 15, 2017 at 12:45

Hello Nesrine, thank you for your reply. I sent also a message to the STM online support and someone answered me.

We have found the problem.

In fact our device sometimes boot in USART mode.

In STM32L151VE MCU, USART1 RX pin used in Bootloader is the PA10. For our design we use the same connector for USB or RS485 communications. And USB+ data line is connected to the PA10 (via a trans-receiver) and one other pin dedicated to USB communication.

That means if we go in DFU mode while device is USB connected, as soon as there are activities on the USB+ data line, the Bootloader do a bad interpretation and goes in USART mode.

If we go in DFU mode without USB cable plugged, we don't have this problem. Enumeration device is always successful in Windows 10.

Thus it is finally more a electronic design error.

Best regards,

François