VBUS usage by bootloader.

re.wolff9 · ‎2016-02-16

Posted on February 16, 2016 at 10:36

I have a board that has an STM32F405 with the USB pins routed to the USB connector. I had problems getting that board to boot, and I was unable to get it to work as DFU device on USB.

One of the possible causes is that the DFU firmware uses VBUSSENSE. That would mean that the device waits for vbus before activating the USB interface. Could that be the case? I have not hooked up the VBUSSENSE line to the CPU.

Does anybody know if the F405 uses VBUSSENSE in the DFU bootloader?

waclawek.jan · ‎2016-02-16

Posted on February 16, 2016 at 14:06

Shouldn't this information be in AN2606 ?

JW

re.wolff9 · ‎2016-02-16

Posted on February 16, 2016 at 23:14

I agree it defintively should!

waclawek.jan · ‎2016-02-16

Posted on February 17, 2016 at 06:51

Okay, so once VBUS isn't mentioned in the AN, couldn't we infer that it is not used in the default USB DFU bootloader? Can't the source of your trouble be of another origin - power supply stability/rise time, instable/inappropriate clock, bootloader inadvertently starting with another peripheral (USART, SPI, I2C) due to externally-driven activity at bootloader-related pins?

JW

re.wolff9 · ‎2016-02-20

Posted on February 20, 2016 at 11:24

Yeah, but the board in question is still quite ''bare'' in that I haven't yet connected the hardware that it is supposed to be driving later on. And the design is copied from a board where the DFU bootloader is shown-to-work, albeit maybe not for the F405.

This issue was ''important'' because I couldn't get the board to work at all. I.e. no reply from either the debugger or DFU.... The debugger started working, so I can now program the chip and proceed with the project. But still it would be nice to know if the DFU bootloader is supposed to work. If it does, I could sell the boards and know that my clients have the hardware to program the chips (i.e. nothing needed beyond an USB cable)....

re.wolff9 · ‎2016-02-22

Posted on February 22, 2016 at 13:56

OK! Update for those following this....

I had a short under the USB connector. That's why it wouldn't boot from USB. So I now have confirmation: the bootloader uses ''NOVBUSSENS'' and will work without a VBUS sense line connected.

(the other board didn't have the short, but I didn't modify it for ''boot from USB'').

waclawek.jan · ‎2016-02-24

Posted on February 25, 2016 at 03:01

Thanks for coming back with that piece of info.

JW