Electronic – STM32: Minimal USB bootloader circuit

bootloaderstm32usb

I would like to use the builtin USB DFU bootloader of STM32F107 chip. My MCU is powered by the device, I don't need to use 5V from the USB.

So far I have connected pins PA11, PA12 and GND directly to a USB cable, but the computer does nothing when I attach the device (I have the BOOT0 pin tied to 3V3).

STM32F107 pin assignments taken from datasheet

When I was studying STM32 bootloader details, I noticed that the bootloader also uses OTG_FS_VBUS pin PA9 – probably to detect connection of USB cable.
On the other hand, another guy here uses pin PA10 to do the same thing. Now I am a bit confused.

What pins should I connect to be able to use USB DFU bootloader? Also sometimes there is a pull-up resistor at DP line in schematics from the internet. Is it necessary?

Thank you for your suggestions, have a nice time 🙂
Klasyc

Best Answer

Can't comment so putting here as an answer. AN2606, page 15 states:

If DFU is used to connect to the bootloader: the USART1_RX (PA10), USART2_RX (PD6) and CAN2_RX (PB5) pins have to be kept at a high or low level and must not be left floating during the detection phase.

Also BOOT1 shall be tied LOW (page 8).

USB DP shall be controlled by MCU - bootloader sets USB DFU Device mode so pullup R should be unnecessary.

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