cancel
Showing results for 
Search instead for 
Did you mean: 

About the DFU mode on a WeAct "BlackPill V2.0" - stm32F411. On the website : DFU Mode: Use the data line to connect to the computer. If there is an unrecognized problem, you can heat the chip appropriately (25°C) and then re-enter the ISP mode ....

jlecl.1
Associate III

Could some one tell me explain why ?

1 ACCEPTED SOLUTION

Accepted Solutions

As Peter said above, the issue is related to HSI precision and frequency change with temperature, because HSI used to determine the crystal's frequency.

JW

View solution in original post

6 REPLIES 6
Peter BENSCH
ST Employee

Welcome, @jlecl.1​, to the community!

One can only assume, because this is a hint from WeActStudio and not from ST.

Presumably they pointed it out on their Github site because it detunes the crystal oscillator a little and they hope that the slightly changed frequency will cause the DFU mode to synchronise.

Does it answer your question?

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
jlecl.1
Associate III

The crystal detunes was my first idea. 

As the advice to maintain at 25° the µC and not the crytal,I would like to knwo is there i some advice for DFU that I haven't read :)

Well, that's in AN2606: STM32 microcontroller system memory boot mode, at the end of section 4.1:

For STM32 devices embedding bootloader using the DFU/CAN interface in which the external clock source (HSE) is required for DFU/CAN operations, the detection of the HSE value is done dynamically by the bootloader firmware and is based on the internal oscillator clock (HSI, MSI). When (because of temperature variations or other conditions) the internal oscillator precision is altered above the tolerance band (1% around the theoretical value), the bootloader might calculate a wrong HSE frequency value. In this case, the bootloader DFU/CAN interfaces might malfunction or not work at all.

I can only assume that WeActStudio hopes to get into the frequency band mentioned with the temperature change.

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
AScha.3
Chief III

maybe just a joke. (the chance to have a wrong setting pll is the reason for connection problem and some 25° clears this problem is about - try it at full moon. then it will work. )

if driver for usb/stm-dfu-device is on system, dfu device will be enumerated. otherwise - not.

heat up or freeze will change nothing.

If you feel a post has answered your question, please click "Accept as Solution".

As Peter said above, the issue is related to HSI precision and frequency change with temperature, because HSI used to determine the crystal's frequency.

JW

jlecl.1
Associate III

perfect, it's clear for me.

Thanks all !