2018-09-01 10:03 AM
When I put 3.3V to boot0 and 0V to boot1 and then 0V to NRST,
I don't get DFU mode. I have to cycle power withboot0 HI to the MCU to get DFU mode.
The docs suggest different. have I misinterpreted the docs?
Thanks, John
2018-09-01 11:17 AM
The System Loader is entered when BOOT0=High
USB connectivity might be an issue if your external oscillator/clock source is slow to start properly.
The PC would also need to sense a change in state on the USB connection. VBUS would need to be able to pulse DP
AN2606 and AN3156 cover some of the details
On my F2/F4 boards a can jump into the ROM from a terminal console, and it connects via USB/DFU, so power cycling definitely isn't a requirement.
Other boards (Flight Controllers) I've had to press a BOOT button and plug in USB while holding it.