Pin assignment BOOT_0 / 1 and USB_DM / DP

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Hello everyone,

I'm working on STM32F401RE and I'm in the middle of designing a circuit.

I have 2 questions:

1- Is it possible to use the USB_DP & USB_DM (PA_11 / PA_12) pins in serial TX & RX mode in addition to the USB_DFU mode? I mean, can I physically have 2 functions on the same pin? As the USB_DFU only injects the .bin when BOOT_0 is pressed.

2 Is it possible to use the BOOT_0 & BOOT_1 (BOOT_0/ PB_2) pins in IO once the MCU has started up? I specify that I use these pins to start the MCU in DFU mode?

Thank you in advance for your reply.

Antoine

[TDK · Accepted solution]

You can use PA11/PA12 as USB for bootloader, and UART in your program, provided that your pullup scheme for UART is compatible with USB. I doubt an external pullup will be acceptable here.

It's not possible to use BOOT0 as a GPIO. You can use PB2 normally after startup.

This chip doesn't have a BOOT1 pin per the datasheet. Could be an omission, could mean BOOT1=0 always.