AN4157

Peripheral firmware examples description

Doc ID 023629 Rev 1

13/24

Stop mode

●

RTC clocked by LSI

●

Regulator in low-power mode

●

HSI and HSE OFF. LSI if not used as RTC clock source

●

No IWDG

●

Flash memory in deep power-down mode

●

Automatic Wakeup using RTC clocked by LSI

Standby mode

●

RTC OFF

●

IWDG and LSI OFF

●

Wakeup using Wakeup Pin (PA.00)

Standby mode with RTC clocked by LSI

●

RTC clocked by LSI

●

IWDG OFF and LSI OFF if not used as RTC clock source

●

Automatic Wakeup using RTC clocked by LSI

3.13

Standby mode example

3.13.1

Purpose

This example shows how to put the STM32F30x/31x in Standby mode and wake it up from

this mode using RTC Alarm A external reset.

3.13.2

Description

In this example:

●

The SysTick timer is initialized.

●

The SysTick timer interrupt is enabled in the NVIC.

●

The SysTick timer/counter starts in free running mode to generate periodic interrupts.

The SysTick timer interrupt is triggered every 250 ms. In the SysTick interrupt handler,

LED3 is toggled; this is used to indicate whether the MCU is in Standby or Run mode.

●

The EXTI line 0 is configured to generate an interrupt on each rising/falling edge

detected on the PA0 pin. The external interrupt is generated every time the PA0

changes level (GND or VDD).

When a falling or rising edge is detected on the EXTI line, an interrupt is generated. In

the EXTI handler routine, the RTC is configured to generate an Alarm event in 3

seconds, after which the system enters Standby mode and LED3 is Off.

After waking-up from Standby mode, the program execution restarts in the same way as

after a reset; the RTC configuration (clock source, prescaler) is kept and LED3 toggles

again. As a result, there is no need to configure the RTC.