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J
JPortilha
Associate III
April 30, 2026
Question

STM32U5 Stop mode with FreeRTOS

  • April 30, 2026
  • 3 replies
  • 158 views

Hello,

I am using an STM32U585 with STOP mode and FreeRTOS in tickless idle mode. The datasheet says the current consumption should be around 4.5uA, however I am measuring 35uA on my custom board that only has the MCU and some decoupling capacitators. Can someone tell me if I need to add something in the code to lower consumption? Are the datasheet consumptions possible running an RTOS? I will leave my code and measurements in attach:

void PreSleepProcessing(uint32_t ulExpectedIdleTime)
{
/* place for user code */
	(void)ulExpectedIdleTime;
 __HAL_RCC_GPIOC_CLK_DISABLE();
 __HAL_RCC_GPIOH_CLK_DISABLE();
 __HAL_RCC_GPIOA_CLK_DISABLE();
 __HAL_RCC_GPIOB_CLK_DISABLE();
	HAL_ICACHE_Disable();
	HAL_SuspendTick();
	HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);
}

void PostSleepProcessing(uint32_t ulExpectedIdleTime)
{
/* place for user code */
	(void)ulExpectedIdleTime;
	SystemClock_Config();
	__HAL_RCC_GPIOC_CLK_ENABLE();
	__HAL_RCC_GPIOH_CLK_ENABLE();
	__HAL_RCC_GPIOA_CLK_ENABLE();
	__HAL_RCC_GPIOB_CLK_ENABLE();
	HAL_ICACHE_Enable();
	HAL_ResumeTick();
}

static void SystemPower_Config(void)
{

 /*
 * SRAM Power Down In Stop Mode Config
 */
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM1_PAGE1_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM1_PAGE2_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM1_PAGE3_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM2_PAGE1_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM2_PAGE2_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE1_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE2_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE3_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE4_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE5_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE6_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE7_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE8_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM4_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_ICACHE_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_DCACHE1_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_DMA2DRAM_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_PKA32RAM_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_PERIPHRAM_FULL_STOP_RETENTION);
/* USER CODE BEGIN PWR */
/* USER CODE END PWR */
}

void SystemClock_Config(void)
{
 RCC_OscInitTypeDef RCC_OscInitStruct = {0};
 RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

 /** Configure the main internal regulator output voltage
 */
 if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE4) != HAL_OK)
 {
 Error_Handler();
 }

 /** Initializes the CPU, AHB and APB buses clocks
 */
 RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSI|RCC_OSCILLATORTYPE_MSI;
 RCC_OscInitStruct.LSIState = RCC_LSI_ON;
 RCC_OscInitStruct.MSIState = RCC_MSI_ON;
 RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
 RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_4;
 RCC_OscInitStruct.LSIDiv = RCC_LSI_DIV1;
 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
 if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
 {
 Error_Handler();
 }

 /** Initializes the CPU, AHB and APB buses clocks
 */
 RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
 |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2
 |RCC_CLOCKTYPE_PCLK3;
 RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
 RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
 RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
 RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 RCC_ClkInitStruct.APB3CLKDivider = RCC_HCLK_DIV1;

 if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
 {
 Error_Handler();
 }

 /** Enable the force of MSIK in stop mode
 */
 __HAL_RCC_MSIKSTOP_ENABLE();
}

3 replies

S
Saket_Om
Technical Moderator
April 30, 2026

Hello @JPortilha 

To better isolate the source of the higher current consumption, could you please perform a first measurement in STOP2 mode without FreeRTOS enabled. 

"To give better visibility on the answered topics, please click on ""Accept as Solution"" on the reply which solved your issue or answered your question.Saket_Om"
J
JPortilhaAuthor
Associate III
April 30, 2026

Hello, I have used this code to measure STOP2 mode in bare metal.

 __HAL_RCC_PWR_CLK_ENABLE();

 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM1_PAGE1_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM1_PAGE2_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM1_PAGE3_STOP_RETENTION);
// HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM2_PAGE1_STOP_RETENTION);
// HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM2_PAGE2_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE1_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE2_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE3_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE4_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE5_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE6_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE7_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM3_PAGE8_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_SRAM4_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_ICACHE_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_DCACHE1_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_DMA2DRAM_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_PKA32RAM_FULL_STOP_RETENTION);
 HAL_PWREx_DisableRAMsContentStopRetention(PWR_PERIPHRAM_FULL_STOP_RETENTION);

 /* USER CODE END 2 */

 /* Infinite loop */
 /* USER CODE BEGIN WHILE */
 while (1)
 {
 /* USER CODE END WHILE */

	HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_12);
	HAL_SuspendTick();
	if (HAL_RTCEx_SetWakeUpTimer_IT(&hrtc, 40000, RTC_WAKEUPCLOCK_RTCCLK_DIV16, 0) != HAL_OK)
	{
		Error_Handler();
	}

	HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);

	SystemClock_Config();
	HAL_ResumeTick();

 /* USER CODE BEGIN 3 */
 }
 /* USER CODE END 3 */
}

I got around 12uA. This is way better than using FreeRTOS, however its still far from the 4.5uA advertised in the datasheet. Do you have any hints?
image (10).png

BR.

S
Saket_Om
Technical Moderator
April 30, 2026

Hello @JPortilha 

Please refer to the article below which cover the needed steps to use the FreeRTOS™ in tickless mode, specifically entering in STOP2 low-power mode with the STM32U5.

How to use STM32U5 with FreeRTOS™ in tickless mode - STMicroelectronics Community

"To give better visibility on the answered topics, please click on ""Accept as Solution"" on the reply which solved your issue or answered your question.Saket_Om"
J
JPortilhaAuthor
Associate III
May 4, 2026

Hello, I have already done all that and I still don´t get the consumptions advertised in the datasheet. What else can I do?

BR.

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