Backup registers controller

[Shuya Nakagawa]

Hello,

I'm currently working to use the backup registers in STM32L452REI6's RTC and I couldn't find any method about those registers.
The code below is my simple test code which is based on the 'SimpleRTC' example.
This seems to work well only on the L452RE, however I didn't test any other STM32 chips because I don't have others.

Is it possible to support such methods to set backup registers with STM32RTC.h, or do they already exists?

#include <STM32RTC.h>

/* Get the rtc object */
STM32RTC& rtc = STM32RTC::getInstance();

/* Change these values to set the current initial time */
const byte seconds = 0;
const byte minutes = 0;
const byte hours = 16;

/* Change these values to set the current initial date */
/* Monday 15th June 2015 */
const byte weekDay = 1;
const byte day = 15;
const byte month = 6;
const byte year = 15;

uint32_t rtc_read_backup_reg(uint32_t BackupRegister) {
    RTC_HandleTypeDef RtcHandle;
    RtcHandle.Instance = RTC;
    return HAL_RTCEx_BKUPRead(&RtcHandle, BackupRegister);
}
 
void rtc_write_backup_reg(uint32_t BackupRegister, uint32_t data) {
    RTC_HandleTypeDef RtcHandle;
    RtcHandle.Instance = RTC;
    HAL_PWR_EnableBkUpAccess();
    HAL_RTCEx_BKUPWrite(&RtcHandle, BackupRegister, data);
    HAL_PWR_DisableBkUpAccess();
}

void setup()
{
  Serial.begin(9600);

  // Select RTC clock source: LSI_CLOCK, LSE_CLOCK or HSE_CLOCK.
  // By default the LSI is selected as source.
  //rtc.setClockSource(STM32RTC::LSE_CLOCK);

  rtc.begin(); // initialize RTC 24H format

  // Set the time
  rtc.setHours(hours);
  rtc.setMinutes(minutes);
  rtc.setSeconds(seconds);

  // Set the date
  rtc.setWeekDay(weekDay);
  rtc.setDay(day);
  rtc.setMonth(month);
  rtc.setYear(year);

  // you can use also
  //rtc.setTime(hours, minutes, seconds);
  //rtc.setDate(weekDay, day, month, year);
}

void loop()
{
  // Print date...
  Serial.printf("%02d/%02d/%02d ", rtc.getDay(), rtc.getMonth(), rtc.getYear());

  // ...and time
  Serial.printf("%02d:%02d:%02d.%03d\n", rtc.getHours(), rtc.getMinutes(), rtc.getSeconds(), rtc.getSubSeconds());

  rtc_write_backup_reg(0, 123);
  Serial.print(rtc_read_backup_reg(0));

  delay(1000);
}

[Frederic Pillon]

I guess you are looking for that in the core:
https://github.com/stm32duino/Arduino_Core_STM32/blob/master/cores/arduino/stm32/backup.h

[Shuya Nakagawa]

@fpistm Thank you so much!