Recently I was repeatedly plugging and unplugging a custom board based on the Teensy 4.1, and noticed the bootloader seemingly randomly activate (showing up via USB), despite the button not being pressed.
Further investigating, using a second MCU, I automated a process repeatedly enabling and disabling power to the board, while keeping the USB data lines and ground connected. This showed some extremely inconsistent behavior, where every 30~120 seconds, the bootloader would inexplicably appear via USB.
As a whole, this behavior is seemingly very random, and I have yet to come up with a consistent reproduction method. I have also been unable to reproduce the issue on a Teensy 4.1, though with the inconsistency around the issue, and my lack of knowledge on it, it's difficult to say that slightly changing the circumstances wouldn't make it occur.
Having listed the context (in case anyone has any ideas on the broader issue), are any cases where the bootloader should activate without the user having pressed the button?
Further investigating, using a second MCU, I automated a process repeatedly enabling and disabling power to the board, while keeping the USB data lines and ground connected. This showed some extremely inconsistent behavior, where every 30~120 seconds, the bootloader would inexplicably appear via USB.
As a whole, this behavior is seemingly very random, and I have yet to come up with a consistent reproduction method. I have also been unable to reproduce the issue on a Teensy 4.1, though with the inconsistency around the issue, and my lack of knowledge on it, it's difficult to say that slightly changing the circumstances wouldn't make it occur.
Having listed the context (in case anyone has any ideas on the broader issue), are any cases where the bootloader should activate without the user having pressed the button?