Nucleo-STM32H563ZI RTC SSR Value Jump Back

[floatsky]

I am programming a Nucleo-STM32H563ZI and get a problem while trying to get subseconds value in RTC.

Below is the main code:

  unsigned prev_ssr = 0;
  char print_buf[32] = { 0 };
  unsigned this_ssr;
  int count;
  while (1)
  {
	  this_ssr = READ_REG(RTC->SSR);
	  if (this_ssr != prev_ssr) {
		  count = sprintf(print_buf, "%05u-->%05u\n", prev_ssr, this_ssr);
		  HAL_UART_Transmit(&huart3, (uint8_t const*)print_buf, count, 10);
		  prev_ssr = this_ssr;
	  }
  }

SSR SynchPrediv is 255 as default. It takes about 3.9ms to decrease by 1.

UART baudrate is 115200. It takes about 1.2ms to send a data package which has 14 bytes.

So this program could catch every normal change of SSR value. And the UART output data verify this.

But in the UART output data, I found some lines like this:

00030-->00029
00029-->00028
00028-->00031
00031-->00027
00027-->00026
00026-->00025

That tells us the SSR value would jump back sometimes.

And it happens about 3 or 4 times per second! I don't know whether some jumps escape.

The jump back value is always 3 (31-8= 3).

Do I take some mistake in STM32CubeIDE project or my code?

[Peter BENSCH]

Welcome @floatsky, to the community!

You are reading a shadow register. Your problem has already been discussed e.g. here, probably that will help you too?

Regards
/Peter

[floatsky]

@Peter BENSCHThanks for attention.

I read the topic you mentioned. I get the knowledge that CR.BYPSHAD and ICSR.RSF work together to synchronize the 3 registers: SSR, TR, DR. Thank you for your information.

The problem in that topic looks like the same with mine. But they are not.

In my program, I read only one register, SSR, not all of the 3.

I modify my program as below:

1. Verify that BYPSHAD is 0, which is default.

2. Clear RSF and wait until it's set again by RTC hardware.

3. Read the 3 registers in the order of SSR, TR, DR.

  /* USER CODE BEGIN WHILE */
	unsigned prev_ssr = 0;
	unsigned this_ssr, tick, tr, dr;
	int count;
	char print_buf[32] = { 0 };
	while (1) {
		/* Unlock write protection */
		WRITE_REG(RTC->WPR, 0xCA);
		WRITE_REG(RTC->WPR, 0x53);
		/* Clear Registers Synchronization Flag(RSF) */
		CLEAR_BIT(RTC->ICSR, (1U << 5));
		/* Reactivate write protection */
		WRITE_REG(RTC->WPR, 0x11);
		/* Wait for hardware setting RSF to 1 */
		while ((READ_REG(RTC->ICSR) & (1U << 5)) == 0)
			;
		/* Read all 3 registers. */
		this_ssr = READ_REG(RTC->SSR);
		tr = READ_REG(RTC->TR);
		dr = READ_REG(RTC->DR);

		tick = HAL_GetTick();
		if (this_ssr != prev_ssr) {
			count = sprintf(print_buf, "%05u:%08u\n", this_ssr, tick);
			HAL_UART_Transmit(&huart3, (uint8_t const*) print_buf, count, 10);
			prev_ssr = this_ssr;
		}
    /* USER CODE END WHILE */

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

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But the result does not change. I'm not sure I've wrote the right code. If there is something wrong in it, please let me know.

I also try another way: set BYPSHAD to 1:

  /* USER CODE BEGIN WHILE */
	unsigned prev_ssr = 0;
	unsigned this_ssr, tick;
	int count;
	char print_buf[32] = { 0 };
	/* Unlock write protection */
	WRITE_REG(RTC->WPR, 0xCA);
	WRITE_REG(RTC->WPR, 0x53);
	/* Set BYPSHAD to 1 */
	SET_BIT(RTC->CR, (1U << 5));
	/* Reactivate write protection */
	WRITE_REG(RTC->WPR, 0x11);
	while (1) {
		this_ssr = READ_REG(RTC->SSR);
		tick = HAL_GetTick();
		if (this_ssr != prev_ssr) {
			count = sprintf(print_buf, "%05u:%08u\n", this_ssr, tick);
			HAL_UART_Transmit(&huart3, (uint8_t const*) print_buf, count, 10);
			prev_ssr = this_ssr;
		}
    /* USER CODE END WHILE */

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

Jumps much fewer than that while BYPSHAD equals 0. But in idea, there should be none. And indeed there's none in Nucleo-F030R8 and STM32F746G-DISCO.

I wrote a python script to assist analyzing serial output.

import re
from serial import Serial
from sys import stderr

# Usage:
# 1. Give a correct serial port name to the variable "port" below.
# 2. Plug development board to PC.
# 3. Debug the program using your prefer IDE. Pause at the entry main function.
# 3. Run this script. Wait until it output "Let's go!" to console.
# 4. Resume the program and keep it running.

pattern = re.compile(r'(\d+):(\d+)')
port = '/dev/ttyACM0'
serial = Serial(port, baudrate=115200, timeout=1)
count = 10000
prev_ssr = 0
summer = dict()
total = 0
log = open('SSR.log', 'w')
# skip garbage data
while serial.read_until(b'\n') != b'':
    pass
print("Let's go!")
serial.timeout = None
for i in range(count):
    line = serial.read_until(b'\n').decode().strip()
    log.write(f'{i:05}:{line}\n')
    match = re.match(pattern, line)
    if not match:
        print(f'Corrupted data line:[{line}]', file=stderr)
        break
    ssr_s, tick_s = match.groups()
    ssr = int(ssr_s)
    if ssr != prev_ssr:
        diff = prev_ssr - ssr
        if diff == 1 or (prev_ssr == 0 and ssr == 255):
            pass
        else:
            total += 1
            summer[diff] = summer.get(diff, 0) + 1
            message = f'NO.{total:05} Jump. Prev: {prev_ssr:05}, Curr: {ssr:05}, Diff: {diff:05}, Line: {i:05}'
            print(message, file=stderr)
        prev_ssr = ssr
    else:
        message = f'Same value neighbors, at line {i:05}'
        print(message, file=stderr)

log.close()
serial.close()

print(f'Total jumps: {total}.')
print(summer)

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And I find that I make a mistake in my first post: the jump back value is not always 3. Most of them are 3, not all.

Below is the main source code.

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2024 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <stdio.h>
/* 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 ---------------------------------------------------------*/

DCACHE_HandleTypeDef hdcache1;

RTC_HandleTypeDef hrtc;

UART_HandleTypeDef huart3;

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_ICACHE_Init(void);
static void MX_RTC_Init(void);
static void MX_USART3_UART_Init(void);
static void MX_DCACHE1_Init(void);
/* 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();
  MX_ICACHE_Init();
  MX_RTC_Init();
  MX_USART3_UART_Init();
  MX_DCACHE1_Init();
  /* USER CODE BEGIN 2 */

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
	unsigned prev_ssr = 0;
	unsigned this_ssr, tick, tr, dr;
	int count;
	char print_buf[32] = { 0 };
	while (1) {
		/* Unlock write protection */
		WRITE_REG(RTC->WPR, 0xCA);
		WRITE_REG(RTC->WPR, 0x53);
		/* Clear Registers Synchronization Flag(RSF) */
		CLEAR_BIT(RTC->ICSR, (1U << 5));
		/* Reactivate write protection */
		WRITE_REG(RTC->WPR, 0x11);
		/* Wait for hardware setting RSF to 1 */
		while ((READ_REG(RTC->ICSR) & (1U << 5)) == 0)
			;
		/* Read all 3 registers. */
		this_ssr = READ_REG(RTC->SSR);
		tr = READ_REG(RTC->TR);
		dr = READ_REG(RTC->DR);

		tick = HAL_GetTick();
		if (this_ssr != prev_ssr) {
			count = sprintf(print_buf, "%05u:%08u\n", this_ssr, tick);
			HAL_UART_Transmit(&huart3, (uint8_t const*) print_buf, count, 10);
			prev_ssr = this_ssr;
		}
    /* USER CODE END WHILE */

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

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Configure the main internal regulator output voltage
  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE0);

  while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}

  /** Configure LSE Drive Capability
  */
  HAL_PWR_EnableBkUpAccess();
  __HAL_RCC_LSEDRIVE_CONFIG(RCC_LSEDRIVE_LOW);

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSE|RCC_OSCILLATORTYPE_CSI;
  RCC_OscInitStruct.LSEState = RCC_LSE_ON;
  RCC_OscInitStruct.CSIState = RCC_CSI_ON;
  RCC_OscInitStruct.CSICalibrationValue = RCC_CSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLL1_SOURCE_CSI;
  RCC_OscInitStruct.PLL.PLLM = 1;
  RCC_OscInitStruct.PLL.PLLN = 125;
  RCC_OscInitStruct.PLL.PLLP = 2;
  RCC_OscInitStruct.PLL.PLLQ = 2;
  RCC_OscInitStruct.PLL.PLLR = 2;
  RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1_VCIRANGE_2;
  RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1_VCORANGE_WIDE;
  RCC_OscInitStruct.PLL.PLLFRACN = 0;
  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_PLLCLK;
  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_5) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief DCACHE1 Initialization Function
  * @param None
  * @retval None
  */
static void MX_DCACHE1_Init(void)
{

  /* USER CODE BEGIN DCACHE1_Init 0 */

  /* USER CODE END DCACHE1_Init 0 */

  /* USER CODE BEGIN DCACHE1_Init 1 */

  /* USER CODE END DCACHE1_Init 1 */
  hdcache1.Instance = DCACHE1;
  hdcache1.Init.ReadBurstType = DCACHE_READ_BURST_WRAP;
  if (HAL_DCACHE_Init(&hdcache1) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN DCACHE1_Init 2 */

  /* USER CODE END DCACHE1_Init 2 */

}

/**
  * @brief ICACHE Initialization Function
  * @param None
  * @retval None
  */
static void MX_ICACHE_Init(void)
{

  /* USER CODE BEGIN ICACHE_Init 0 */

  /* USER CODE END ICACHE_Init 0 */

  ICACHE_RegionConfigTypeDef pRegionConfig = {0};

  /* USER CODE BEGIN ICACHE_Init 1 */

  /* USER CODE END ICACHE_Init 1 */

  /** Configure and enable region 0 for memory remapping
  */
  pRegionConfig.BaseAddress = 0x10000000;
  pRegionConfig.RemapAddress = 0x60000000;
  pRegionConfig.Size = ICACHE_REGIONSIZE_2MB;
  pRegionConfig.TrafficRoute = ICACHE_MASTER1_PORT;
  pRegionConfig.OutputBurstType = ICACHE_OUTPUT_BURST_WRAP;
  if (HAL_ICACHE_EnableRemapRegion(_NULL, &pRegionConfig) != HAL_OK)
  {
    Error_Handler();
  }

  /** Enable instruction cache in 1-way (direct mapped cache)
  */
  if (HAL_ICACHE_ConfigAssociativityMode(ICACHE_1WAY) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_ICACHE_Enable() != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN ICACHE_Init 2 */

  /* USER CODE END ICACHE_Init 2 */

}

/**
  * @brief RTC Initialization Function
  * @param None
  * @retval None
  */
static void MX_RTC_Init(void)
{

  /* USER CODE BEGIN RTC_Init 0 */

  /* USER CODE END RTC_Init 0 */

  RTC_PrivilegeStateTypeDef privilegeState = {0};
  RTC_TimeTypeDef sTime = {0};
  RTC_DateTypeDef sDate = {0};

  /* USER CODE BEGIN RTC_Init 1 */

  /* USER CODE END RTC_Init 1 */

  /** Initialize RTC Only
  */
  hrtc.Instance = RTC;
  hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
  hrtc.Init.AsynchPrediv = 127;
  hrtc.Init.SynchPrediv = 255;
  hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
  hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
  hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
  hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
  hrtc.Init.OutPutPullUp = RTC_OUTPUT_PULLUP_NONE;
  hrtc.Init.BinMode = RTC_BINARY_NONE;
  if (HAL_RTC_Init(&hrtc) != HAL_OK)
  {
    Error_Handler();
  }
  privilegeState.rtcPrivilegeFull = RTC_PRIVILEGE_FULL_NO;
  privilegeState.backupRegisterPrivZone = RTC_PRIVILEGE_BKUP_ZONE_NONE;
  privilegeState.backupRegisterStartZone2 = RTC_BKP_DR0;
  privilegeState.backupRegisterStartZone3 = RTC_BKP_DR0;
  if (HAL_RTCEx_PrivilegeModeSet(&hrtc, &privilegeState) != HAL_OK)
  {
    Error_Handler();
  }

  /* USER CODE BEGIN Check_RTC_BKUP */

  /* USER CODE END Check_RTC_BKUP */

  /** Initialize RTC and set the Time and Date
  */
  sTime.Hours = 12;
  sTime.Minutes = 34;
  sTime.Seconds = 56;
  sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
  sTime.StoreOperation = RTC_STOREOPERATION_RESET;
  if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BIN) != HAL_OK)
  {
    Error_Handler();
  }
  sDate.WeekDay = RTC_WEEKDAY_SUNDAY;
  sDate.Month = RTC_MONTH_FEBRUARY;
  sDate.Date = 29;
  sDate.Year = 24;

  if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BIN) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN RTC_Init 2 */

  /* USER CODE END RTC_Init 2 */

}

/**
  * @brief USART3 Initialization Function
  * @param None
  * @retval None
  */
static void MX_USART3_UART_Init(void)
{

  /* USER CODE BEGIN USART3_Init 0 */

  /* USER CODE END USART3_Init 0 */

  /* USER CODE BEGIN USART3_Init 1 */

  /* USER CODE END USART3_Init 1 */
  huart3.Instance = USART3;
  huart3.Init.BaudRate = 115200;
  huart3.Init.WordLength = UART_WORDLENGTH_8B;
  huart3.Init.StopBits = UART_STOPBITS_1;
  huart3.Init.Parity = UART_PARITY_NONE;
  huart3.Init.Mode = UART_MODE_TX_RX;
  huart3.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart3.Init.OverSampling = UART_OVERSAMPLING_16;
  huart3.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart3.Init.ClockPrescaler = UART_PRESCALER_DIV1;
  huart3.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart3) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_UARTEx_SetTxFifoThreshold(&huart3, UART_TXFIFO_THRESHOLD_1_8) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_UARTEx_SetRxFifoThreshold(&huart3, UART_RXFIFO_THRESHOLD_1_8) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_UARTEx_DisableFifoMode(&huart3) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART3_Init 2 */

  /* USER CODE END USART3_Init 2 */

}

/**
  * @brief GPIO Initialization Function
  * @param None
  * @retval None
  */
static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 */

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOF_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOG_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(YELLOW_GPIO_Port, YELLOW_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GREEN_GPIO_Port, GREEN_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(RED_GPIO_Port, RED_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin : Button_Pin */
  GPIO_InitStruct.Pin = Button_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(Button_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : YELLOW_Pin */
  GPIO_InitStruct.Pin = YELLOW_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(YELLOW_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : GREEN_Pin */
  GPIO_InitStruct.Pin = GREEN_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GREEN_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : RED_Pin */
  GPIO_InitStruct.Pin = RED_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(RED_GPIO_Port, &GPIO_InitStruct);

/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @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 */
  __disable_irq();
  while (1)
  {
  }
  /* 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(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

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Appreciate for any help.