very strange STM32F40x RTC issue

[CBerg]

I have a very strange issue with an STM32F405RG/407VG regarding the RTC: it only works, when I am in debugging mode and add the “hrtc�? struct into live expression and the instance handle is open!

My code is pretty simple:

I have 2 globals:

RTC_TimeTypeDef st = {0,};
uint32_t sysTime = 0;

which are globals for debugging purposes,

Hardware Initialisation in main():

/* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_CRC_Init();
  MX_I2C1_Init();
  MX_RNG_Init();
  MX_RTC_Init();
  MX_USB_DEVICE_Init();
  /* USER CODE BEGIN 2 */
  uint16_t led = 500;
  uint32_t sled = 0;
  /* USER CODE END 2 */

a function, that gets the Time from the RTC in *USER CODE 4*:

void GetTime(void) {
	HAL_RTC_GetTime(&hrtc, &st, RTC_FORMAT_BIN);
	sysTime = (((((uint32_t)st.Hours) * 60) + ((uint32_t)st.Minutes)) * 60) + (uint32_t)st.Seconds;
}

And a simple main loop:

while(1) {
	  	if(led) led--;
	  	else {
	  		led = 500;
	  		HAL_GPIO_TogglePin(LED1_GPIO_Port, LED1_Pin);
	  	}
	  	if(sysTime != sled) {
	  		HAL_GPIO_TogglePin(LED2_GPIO_Port, LED2_Pin);
	  		sled = sysTime;
	  	}
 
	  	GetTime();
	  	HAL_Delay(1);
}

The intended behaviour is:

a)   Toggle the LED1 to indicate the program is running

b)   Toggle the LED2 when the “sysTime�? variable has changed.

But what happens instead is:

When I am in debugging mode, and have hrtc->Instance open in the “Live Expressions Window�? LED1 and LED2 toggle as intended.

hrtc->Instance closed => "sysTime" is not updated

 

hrtc->Instance open in Live Expressions => "sysTime" is updated

When I close the debugging mode LED1 keeps toggling, but LED2 stops toggling, which means that “sysTime�? is no longer updated.

Has anyone an idea, what’s going on here?

I am using CubeID 1.9 with F4 Drivers “STM32Cube_FW_F4_V1.27.0�?

Some Additional Info:

This issue popped up in a bigger project with an STM32F407VE. For debugging purposed I build this simple programm on an F405RE, where i could reproduce the behavior.

When I close CubeIDE, remove the power from my test board, and power it up again after a few seconds, the LED2 does not toggle. This means the RTC is dead, except I am in Debuggin mode and having a probe set on hrtc->Instance

The same Code is working well on a Bluepill (F103C8).

[waclawek.jan · Accepted solution]

After reading time, you have to read date too.

JW

[PHolt.1]

There is an additional complication if one reads fractional seconds... a long thread on EEVBLOG and I think here too.

[CBerg]

@JW thank you very much! This did the trick!

My GetTime() function now looks like this:

void GetTime(void) {
	RTC_TimeTypeDef st;
	HAL_RTC_GetTime(&hrtc, &st, RTC_FORMAT_BIN);
        #ifdef __STM32F4xx_HAL_H
	RTC_DateTypeDef sd;
	HAL_RTC_GetDate(&hrtc, &sd, RTC_FORMAT_BIN);
	UNUSED(sd);
        #endif
	sysTime = (((((uint32_t)st.Hours) * 60) + ((uint32_t)st.Minutes)) * 60) + (uint32_t)st.Seconds;
}

@PHolt: luckily i don't need fractional seconds ATM, my "complication bucket" is full for today ;) - but thanks for the warning!