PWR STANDBY Mode Example

  ******************** (C) COPYRIGHT 2014 STMicroelectronics *******************
  * @file    PWR/PWR_STANDBY/readme.txt 
  * @author  MCD Application Team
  * @version V1.4.0
  * @date    24-July-2014
  * @brief   Description of the PWR STANDBY Mode Example.
  ******************************************************************************
  *
  * Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");
  * You may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *        http://www.st.com/software_license_agreement_liberty_v2
  *
  * Unless required by applicable law or agreed to in writing, software 
  * distributed under the License is distributed on an "AS IS" BASIS, 
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  ******************************************************************************
   

PWR/PWR_STANDBY example Description

This example shows how to enter the system to STANDBY mode and wake-up from this mode either with the RESET or using RTC Alarm.

In the associated software, the system clock is set to 48 MHz, the SysTick is programmed to generate an interrupt each 250 ms. In the SysTick interrupt handler, the LED3 is toggled, this is used to indicate whether the MCU is in STANDBY or RUN mode.

When a falling edge is detected on the PC13(pressing on tamper button), the RTC is configured to generate an Alarm event in 3 seconds then the system enters STANDBY mode causing the LED3 to stop toggling. An external RESET will wake-up the system from STANDBY. If within 3 seconds an external RESET is not generated, the RTC Alarm will wake-up the system.

After wake-up from STANDBY mode, program execution restarts in the same way as after a RESET, the LED3 is toggling again,the RTC configuration(clock source, enable, prescaler,...) is kept. As result there is no need to configure the RTC.

Led LED3 is used to monitor the system state as following:

• LED3 toggling: system in RUN mode
• LED3 off : system in STANDBY mode

To cope with the LSI clock inaccuracy, routine of LSI measurement is implemented as follow:

• Configure the TIM14 to remap internally the TIM14 Channel 1 Input Capture to the LSI clock output.
• Enable the TIM14 Input Capture interrupt: after one cycle of LSI clock, the period value is stored in a variable and compared to the HCLK clock to get its real value.
• The RTC prescaler is adjusted with this LSI frequency value so that the RTC CK_SPRE value become more accurate.

Directory contents

• PWR/PWR_STANDBY/stm32f0xx_conf.h Library Configuration file
• PWR/PWR_STANDBY/stm32f0xx_it.c Interrupt handlers
• PWR/PWR_STANDBY/stm32f0xx_it.h Interrupt handlers header file
• PWR/PWR_STANDBY/main.c Main program
• PWR/PWR_STANDBY/main.h Header for main.c module
• PWR/PWR_STANDBY/system_stm32f0xx.c STM32F0xx system source file

Note:

The "system_stm32f0xx.c" is generated by an automatic clock configuration tool and can be easily customized to meet user application requirements. To select different clock setup, use the "STM32F0xx_Clock_Configuration_VX.Y.Z.xls" provided with the AN4055 package available on ST Microcontrollers

Hardware and Software environment

• This example runs on STM32F0xx devices.

• This example has been tested with STMicroelectronics STM320518-EVAL and STM32072B-EVAL including respectively STM32F051R8T6 and STM32F072VBT6 devices and can be easily tailored to any other supported device and development board

• STM320518-EVAL Set-up
  • Use the Tamper push-button connected to PC13 pin

• STM32072B-EVAL Set-up
  • Use the Tamper push-button connected to PC13 pin

How to use it ?

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

• Copy all source files from this example folder to the template folder under Project
• Open your preferred toolchain
• If the used device is STM32F051R8T6 choose STM32F051 project
  • Add the following files to the project source list
    • Utilities\STM32_EVAL\STM320518_EVAL\stm320518_eval.c
• If the used device is STM32F072VBT6 choose STM32F072 project
  • Add the following files to the project source list
    • Utilities\STM32_EVAL\STM32072B_EVAL\stm32072b_eval.c
• Rebuild all files and load your image into target memory
• Run the example

© COPYRIGHT STMicroelectronics