How to enter the Standby mode and wake up from this mode by using an external reset or the WKUP pin.
In the associated software, the system clock is set to 48 MHz, an EXTI line is connected to the pin PC.13 and configured to generate an interrupt on falling edge. 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 Standby or Run mode.
When a falling edge is detected on the EXTI line, an interrupt is generated and the system wakes up the program then checks and clears the standby flag. After clearing the standby flag, the software enables wake-up pin PWR_WAKEUP_PIN2 connected to PC.13, then the corresponding flag indicating that a wakeup event was received from the PWR_WAKEUP_PIN2 is cleared. Finally, the system enters again Standby mode causing LED1 to stop toggling.
Next, the user can wake-up the system in pressing the User push-button which is connected to the wake-up pin PWR_WAKEUP_PIN2. A falling edge on WKUP pin will wake-up the system from Standby. Alternatively, an external RESET of the board will lead to a system wake-up as well.The application needs to ensure that the SysTick
After wake-up from Standby mode, program execution restarts in the same way as after a RESET and LED1 restarts toggling.
LED1 is used to monitor the system state as follows:
To measure the current consumption in Standby mode, remove JP5 jumper and connect an amperemeter to JP5 to measure IDD current.
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.
The application needs to ensure that the SysTick time base is always set to 1 millisecond to have correct HAL operation.
Power, PWR, Standby mode, Interrupt, EXTI, Wakeup, Low Power, External reset
- PWR/PWR_STANDBY/Inc/stm32c0xx_conf.h HAL Configuration file
- PWR/PWR_STANDBY/Inc/stm32c0xx_it.h Header for stm32c0xx_it.c
- PWR/PWR_STANDBY/Inc/main.h Header file for main.c
- PWR/PWR_STANDBY/Src/system_stm32c0xx.c STM32C0xx system clock configuration file
- PWR/PWR_STANDBY/Src/stm32c0xx_it.c Interrupt handlers
- PWR/PWR_STANDBY/Src/main.c Main program
- PWR/PWR_STANDBY/Src/stm32c0xx_hal_msp.c HAL MSP module
This example runs on STM32C071RBTx devices
This example has been tested with STMicroelectronics NUCLEO-C071RB board and can be easily tailored to any other supported device and development board.
NUCLEO-C071RB Set-up
In order to make the program work, you must do the following :