PWR_SLEEP Example Description

How to enter the Sleep mode and wake up from this mode by using an interrupt.

In the associated software, the system clock is set to 48 MHz. an EXTI line is connected to the Joystick Selection push-button through PA.04 and configured to generate an interrupt on falling edge upon key press. The SysTick is programmed to generate an interrupt each 1 ms and in the SysTick interrupt handler, LED1 is toggled in order to indicate whether the MCU is in SLEEP mode or RUN mode.

5 seconds after start-up, the system automatically enters SLEEP mode and LED1 stops toggling.

LED1 is used to monitor the system state as follows:

These steps are repeated in an infinite loop.

Notes

  1. This example can not be used in DEBUG mode due to the fact that the Cortex-M0+ core is no longer clocked during low power mode so debugging features are disabled.

  2. Care must be taken when using HAL_Delay(), this function provides accurate delay (in milliseconds) based on variable incremented in SysTick ISR. This implies that if HAL_Delay() is called from a peripheral ISR process, then the SysTick interrupt must have higher priority (numerically lower) than the peripheral interrupt. Otherwise the caller ISR process will be blocked. To change the SysTick interrupt priority you have to use HAL_NVIC_SetPriority() function.

  3. The application needs to ensure that the SysTick time base is always set to 1 millisecond to have correct HAL operation.

Keywords

Power, PWR, EXTI, Sleep mode, Interrupt, Wakeup, External reset

Directory contents

Hardware and Software environment

How to use it ?

In order to make the program work, you must do the following :