Thu Sep 5 21:46:34 EDT 2019

USB disconnect

Let's try to get that USB pullup resistor off.

EDIT: It is R11 on the recent batch of bluepill boards.  Easy to check
by plugging it into one of the cheap USB hubs that has D+ D- easily
accessible, and then just beeping it out.

EDIT: R11 is the one that is connected to D+, but it is not the pullup.

How to mod the board?  Take off R10, and flip it over to the nearest
GPIO which is B3.  I hope that's not the LED.  Nope that's C13.

Dammit B3 is part of debug interface.
B5 is the closest one.

Ok that works.

But it doesn't come back up after reset.

STM32F4 usb can do a 'soft disconnect'  OTG_FS_DCTL SDIS

Peripheral states

EDIT: A11 (D-) and A12 (D+) are actually just on the pins.

Currently I don't have a good solution for reset.  I don't understand
why it doesn't re-enumerate on reset.  Also when I just replug the
micro usb it doesn't re-enumerate ether.

But that works in the other hub.

And there reset also works.

Odd, the back side ports of that amazon hub do work ok.

So now it just needs a reset.  Watchdog is probably simplest.