This application demonstrates the use of FreeRTOS tickless low power mode and semaphores.
The system relies on a low power timer to wake up from its low power state.
The thread blocks on a semaphore. This causes the system to start the low power timer and enter STOP mode.
Once the timer expires, an interrupt is triggered and the CPU returns to RUN mode. The semaphore is released in the timer's interrupt handler. The thread resumes execution and toggles the blue LED.
The green LED is connected to PC7 which is configured to go HIGH whenever the system is in stop mode. In order to reduce power consumption, PC7 can be disabled.
Successful operation is marked by the blue LED toggling every second. The green LED should be ON.
On failure, the red LED is ON.
None
None
To measure the current consumption remove JP5 jumper and connect an ammeter to JP5 to measure IDD current.
This example can not be used in DEBUG mode due to the fact that the Cortex-M33 core is no longer clocked during low power mode so debugging features are disabled.
It is possible to reduce power consumption even further by configuring all pins as analog pins and disabling their clocks.
The FreeRTOS heap size configTOTAL_HEAP_SIZE defined in FreeRTOSConfig.h is set accordingly to the OS resources memory requirements of the application with +10% margin and rounded to the upper Kbyte boundary.
For more details about FreeRTOS implementation on STM32Cube, please refer to UM1722 "Developing Applications on STM32Cube with RTOS".
FreeRTOS, RTOS, LowPower, LPTIM
- This application runs on STM32U575xx devices.
- This application has been tested with STMicroelectronics NUCLEO-U575ZI board MB1549 Rev. C01 and can be easily tailored to any other supported device and development board.
In order to make the program work, you must do the following :
- Open the project in your preferred toolchain
- Rebuild all files and load your image into target memory
- Run the application