LEDs and buttons on STM32 MPU boards

1 Introduction[edit]

STM32 MPU Evaluation boards and Discovery kits share the same usage for LEDs and buttons. The following paragraphs describe the functional mapping of the LEDs and buttons, so that you can refer to the respective board-hardware descriptions to determine to which GPIO each function is mapped:

2 Description[edit]

LED color Button label Purpose
- WAKE UP This button allows the platform to be woken from any low-power mode[1]
Green
(*)
USER1
(*)
This can be used at boot time as a button, by U-Boot, to enter USB programming mode with STM32CubeProgrammer. This avoids manipulation of the boot pins when a valid U-Boot image is already present in the board.

It can be used at runtime as:

  • a LED or a button for Linux examples
  • a button for STM32Cube examples
Red
(*)
USER2
(*)
This can be used at boot time as a button, by U-Boot, to enter Android Fastboot mode.

It is also used as a LED to show Cortex-A boot information[2], then it can be used, at runtime, as a button for Linux examples. It is not used by STM32Cube.

Blue - Linux heartbeat LED, which blinks as long as the Linux[3] is alive[2] on the Cortex-A
Orange - STM32Cube[4] examples verdict LED.
Warning.png (*) Both a LED and a button are connected to the same GPIO, with inverted logic for the LED control (so the LED is switched on when the GPIO output is set low).

3 References[edit]



Microprocessor Unit

General-Purpose Input/Output

Light-emitting diode

uniprocessor

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