tinyusb/stm32_fsdev: Add dcd_connect/dcd_disconnect #3536
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STM32F1/F3 do not have internal pull-up resistor on D+ line that can be automatically attached. Many board have external pull-up resistor that is connected all the time. So far when USB_DP_HAS_EXTERNAL_PULL_UP was 1 (default) code was shorting D+ line to the ground as GPIO output for a wile during startup. It is possible to have external pull-up resistor that is switchable at runtime (via transistor or resistor is just sourced from one of the GPIO pins). For this purpose now dcd_connect and dcd_disconnect functions are provided that can enabled pull-up resistor in several ways. With such setup device that is connected to USB just for power does not have to be detected by host system as broken one. Signed-off-by: Jerzy Kasenberg <[email protected]>
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STM32F1/F3 do not have internal pull-up resistor on D+ line that can be automatically attached.
Many board have external pull-up resistor that is
connected all the time.
So far when USB_DP_HAS_EXTERNAL_PULL_UP was 1 (default) code was shorting D+ line to the ground as GPIO output for a wile during startup.
It is possible to have external pull-up resistor that is switchable at runtime (via transistor or resistor is just sourced from one of the GPIO pins).
For this purpose now dcd_connect and dcd_disconnect functions are provided that can enabled pull-up resistor in several ways.
With such setup device that is connected to USB just for power does not have to be detected by host system as broken one.