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Using Bootloader Via USB With STM32F4

Question asked by ryan.robert on Mar 6, 2013
I am trying to establish a connection with the bootloader via USB using our prototype which has an STM32F407. I know the USB FS connection works because our firmware uses it to connect to the PC. Also, I can get the evaluation board to connect to the PC using USB and its bootloader, so the PC is working ok.

Our device can be powered from a battery or from the USB cable. When powered from the battery, I pull BOOT0 high while resetting, release the reset and then release BOOT0 (it goes back low). The previously loaded firmware does not execute and the processor appears to be in the bootloader. As soon as I plug the USB cable in, the processor appears to leave the bootloader and begins executing the old firmware.

If I disconnect the battery and run off of USB power, I pull BOOT0 high while resetting, release the reset and then release BOOT0 (it goes back low). As soon as I release BOOT0, the old firmware starts to execute.

Any idea what is going on here? I've seen some posts about problems with PA9 but that was a few years ago and appears to have only been and issue with the STM32F1 parts.

Bob

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