How to put a FreeRTOS application in STOP2 mode (STM32L4)

[FGome]

In specific circunstances (power available, ...) I want to put the MCU in STOP2 mode. That decision is taken on a FreeRTOS task. I've tried some approaches but the MCU didn't stop at all. Is there any example available using FreeRTOS? The code I'm using (not working) is the following:

			/* suspend scheduler*/
			vTaskSuspendAll();
 
			/* disables Interrupt requests, interrupts will still be able to wake up the system*/
			__disable_irq();
 
			__HAL_RCC_PWR_CLK_DISABLE();
			__HAL_PWR_CLEAR_FLAG(PWR_FLAG_WU);
 
			HAL_SuspendTick();
			HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);
			HAL_ResumeTick();
 
			/* System sleeps here*/
 
			__HAL_PWR_CLEAR_FLAG(PWR_FLAG_WU);
			/* on wake up, restore system clock*/
			HAL_RCC_DeInit();
			SystemClock_Config();
 
			/* check interrupts now*/
			__enable_irq();
 
			/*resume scheduler*/
			xTaskResumeAll();

Do you have any suggestion to change? In the final code I want it to be able to wake up when some pins change state, and also using the RTC, but for now I was only focused on the MCU stop.

Thanks in advance

Fernando

[turboscrew]

You should look into FreeRTOS "tickless idle", but remember that it's not tickless unless you make it tickless (the name is a bit misleading). Basically, the tickless idle is called, when the OS sees that there is time to sleep (no task needs to run). The maximum sleeping time is given as parameter to the function, and it can also indicate "indefinite time".

Also, there should not be any interrupts pending. If there are, the processor refuses to go into stop mode (the 'wfi' is considered as 'nop').

The debugger can also keep the stop mode from taking place.

[FGome]

Thanks for your answer! Since I'm only using STOP2 mode because I need to wake up on generic GPIO pins but will do a device reset when it wakes (so the behavior is more like in standby mode), will it be possible to stop it even not using tickless idle mode, since I won't need FreeRTOS after waking-up because I'll reset the device?

Best regards

Fernando

[Mohamed Aymen HZAMI]

Hello,

I tried to start from an example that i created from CubeMx, this is the generated main with my modification to implement the STOP2 mode :

/* USER CODE BEGIN Header */
/**
 ******************************************************************************
 * @file : main.c
 * @brief : Main program body
 ******************************************************************************
 * @attention
 *
 * <h2><center>&copy; Copyright (c) 2020 STMicroelectronics.
 * All rights reserved.</center></h2>
 *
 * This software component is licensed by ST under Ultimate Liberty license
 * SLA0044, the "License"; You may not use this file except in compliance with
 * the License. You may obtain a copy of the License at:
 * www.st.com/SLA0044
 *
 ******************************************************************************
 */
/* USER CODE END Header */
 
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "cmsis_os.h"
 
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
 
/* USER CODE END Includes */
 
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
 
/* USER CODE END PTD */
 
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */
 
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
 
/* USER CODE END PM */
 
/* Private variables ---------------------------------------------------------*/
osThreadId defaultTaskHandle;
/* USER CODE BEGIN PV */
 
/* USER CODE END PV */
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
void StartDefaultTask(void const * argument);
 
/* USER CODE BEGIN PFP */
 
/* USER CODE END PFP */
 
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
 
/* USER CODE END 0 */
 
/**
 * @brief The application entry point.
 * @retval int
 */
int main(void)
{
 /* USER CODE BEGIN 1 */
 
 /* USER CODE END 1 */
 
 
 /* MCU Configuration--------------------------------------------------------*/
 
 /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
 HAL_Init();
 
 /* USER CODE BEGIN Init */
 
 /* USER CODE END Init */
 
 /* Configure the system clock */
 SystemClock_Config();
 
 /* USER CODE BEGIN SysInit */
 
 /* USER CODE END SysInit */
 
 /* Initialize all configured peripherals */
 MX_GPIO_Init();
 /* USER CODE BEGIN 2 */
 
 /* USER CODE END 2 */
 
 /* USER CODE BEGIN RTOS_MUTEX */
 /* add mutexes, ... */
 /* USER CODE END RTOS_MUTEX */
 
 /* USER CODE BEGIN RTOS_SEMAPHORES */
 /* add semaphores, ... */
 /* USER CODE END RTOS_SEMAPHORES */
 
 /* USER CODE BEGIN RTOS_TIMERS */
 /* start timers, add new ones, ... */
 /* USER CODE END RTOS_TIMERS */
 
 /* USER CODE BEGIN RTOS_QUEUES */
 /* add queues, ... */
	
	/* suspend scheduler*/
	HAL_Delay(1000);
		
 /* USER CODE END RTOS_QUEUES */
 
 /* Create the thread(s) */
 /* definition and creation of defaultTask */
 osThreadDef(defaultTask, StartDefaultTask, osPriorityNormal, 0, 128);
 defaultTaskHandle = osThreadCreate(osThread(defaultTask), NULL);
 
 /* USER CODE BEGIN RTOS_THREADS */
 /* add threads, ... */
 /* USER CODE END RTOS_THREADS */
 
 /* Start scheduler */
 osKernelStart();
 
 /* We should never get here as control is now taken by the scheduler */
 
 /* Infinite loop */
 /* USER CODE BEGIN WHILE */
 while (1)
 {
 /* USER CODE END WHILE */
 
 /* USER CODE BEGIN 3 */
		HAL_GPIO_WritePin(LD2_GPIO_Port,LD2_Pin,GPIO_PIN_SET);
		HAL_Delay(100);
		HAL_GPIO_WritePin(LD2_GPIO_Port,LD2_Pin,GPIO_PIN_RESET);
		HAL_Delay(100);
 }
 /* USER CODE END 3 */
}
 
/**
 * @brief System Clock Configuration
 * @retval None
 */
void SystemClock_Config(void)
{
 RCC_OscInitTypeDef RCC_OscInitStruct = {0};
 RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
 
 /** Initializes the CPU, AHB and APB busses clocks 
 */
 RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
 RCC_OscInitStruct.HSIState = RCC_HSI_ON;
 RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
 RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
 RCC_OscInitStruct.PLL.PLLM = 1;
 RCC_OscInitStruct.PLL.PLLN = 10;
 RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV7;
 RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
 RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
 if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
 {
 Error_Handler();
 }
 /** Initializes the CPU, AHB and APB busses clocks 
 */
 RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
 |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
 RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
 RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
 RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
 RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
 if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
 {
 Error_Handler();
 }
 /** Configure the main internal regulator output voltage 
 */
 if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1) != HAL_OK)
 {
 Error_Handler();
 }
}
 
/**
 * @brief GPIO Initialization Function
 * @param None
 * @retval None
 */
static void MX_GPIO_Init(void)
{
 GPIO_InitTypeDef GPIO_InitStruct = {0};
 
 /* GPIO Ports Clock Enable */
 __HAL_RCC_GPIOA_CLK_ENABLE();
 
 /*Configure GPIO pin Output Level */
 HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_RESET);
 
 /*Configure GPIO pin : PA0 */
 GPIO_InitStruct.Pin = GPIO_PIN_0;
 GPIO_InitStruct.Mode = GPIO_MODE_EVT_RISING;
 GPIO_InitStruct.Pull = GPIO_PULLDOWN;
 HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
 /*Configure GPIO pin : LD2_Pin */
 GPIO_InitStruct.Pin = LD2_Pin;
 GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
 HAL_GPIO_Init(LD2_GPIO_Port, &GPIO_InitStruct);
 
}
 
/* USER CODE BEGIN 4 */
 
/* USER CODE END 4 */
 
/* USER CODE BEGIN Header_StartDefaultTask */
/**
 * @brief Function implementing the defaultTask thread.
 * @param argument: Not used 
 * @retval None
 */
/* USER CODE END Header_StartDefaultTask */
void StartDefaultTask(void const * argument)
{
 /* USER CODE BEGIN 5 */
 /* Infinite loop */
	
	HAL_SuspendTick();
	HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFE);
	HAL_ResumeTick();
	HAL_RCC_DeInit();
	
 for(;;)
 {
 osDelay(1);
		HAL_GPIO_WritePin(LD2_GPIO_Port,LD2_Pin,GPIO_PIN_SET);
		osDelay(100);
		HAL_GPIO_WritePin(LD2_GPIO_Port,LD2_Pin,GPIO_PIN_RESET);
		osDelay(100);
 }
 /* USER CODE END 5 */ 
}
 
/**
 * @brief This function is executed in case of error occurrence.
 * @retval None
 */
void Error_Handler(void)
{
 /* USER CODE BEGIN Error_Handler_Debug */
 /* User can add his own implementation to report the HAL error return state */
 
 /* USER CODE END Error_Handler_Debug */
}
 
#ifdef USE_FULL_ASSERT
/**
 * @brief Reports the name of the source file and the source line number
 * where the assert_param error has occurred.
 * @param file: pointer to the source file name
 * @param line: assert_param error line source number
 * @retval None
 */
void assert_failed(char *file, uint32_t line)
{ 
 /* USER CODE BEGIN 6 */
 /* User can add his own implementation to report the file name and line number,
 tex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
 /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
 
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

In StartDefaultTask I put the Stop2 mode function, I also configured the GPIO_PIN PA0 as wake-up (PA0 --> 3.3V) pin.

Note : this example for STM32L476-nucleo board.

Best Regards,

Mohamed Aymen.

[zsellera]

Hi,

I just solved this problem recently using FreeRTOS's configPRE_SLEEP_PROCESSING hooks. I created a blog post about it:

https://kucu.io/2021/03/stm32-deepsleep-modes-stop-stop2-standby-freertos/

Source: https://gist.github.com/zsellera/21ad396f35852a039444c782a69e142e

Best,