I'm not sure what exactly you mean by 'display' (i.e., is it an LCD screen, a serial output-terminal, etc?).
In any case, the RTC is typically connected to the STM32 through an I2C bus, so you will need to initialize both controllers (RTC and I2C) before you can get/set the date and the time on the RTC.
**Here is how you can initialize the RTC controller:**
void rtc_init()
{
RTC_InitTypeDef RTC_InitStructure;
RTC_TimeTypeDef RTC_TimeStruct;
/* Enable the PWR clock */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR,ENABLE);
/* Allow access to RTC */
PWR_BackupAccessCmd(ENABLE);
/* Reset RTC Domain */
RCC_BackupResetCmd(ENABLE);
RCC_BackupResetCmd(DISABLE);
/* Enable the LSE OSC */
RCC_LSEConfig(RCC_LSE_ON);
/* Wait until LSE is ready */
while (RCC_GetFlagStatus(RCC_FLAG_LSERDY) == RESET);
/* Select the RTC Clock Source */
RCC_RTCCLKConfig(RCC_RTCCLKSource_LSE);
/* Configure the RTC data register and RTC prescaler */
RTC_InitStructure.RTC_AsynchPrediv = 0x7F;
RTC_InitStructure.RTC_SynchPrediv = 0xFF;
RTC_InitStructure.RTC_HourFormat = RTC_HourFormat_24;
RTC_Init(&RTC_InitStructure);
/* Set the time to 00h 00mn 00s AM */
RTC_TimeStruct.RTC_H12 = RTC_H12_AM;
RTC_TimeStruct.RTC_Hours = 0x00;
RTC_TimeStruct.RTC_Minutes = 0x00;
RTC_TimeStruct.RTC_Seconds = 0x00;
RTC_SetTime(RTC_Format_BCD,&RTC_TimeStruct);
}
**And here is how you can get/set the date and the time on the RTC, excluding day-of-the-week:**
In the header file:
typedef struct
{
unsigned char second;
unsigned char minute;
unsigned char hour;
unsigned char day;
unsigned char month;
unsigned char year;
}
rtc_data_t;
void rtc_get(rtc_data_t* rtc_data);
void rtc_set(rtc_data_t* rtc_data);
In the source file:
#define SENSOR_ADDRESS 0xD0 // or set this according to your HW configuration
#define HEX_2_DEC(val) (((val)/16)*10+((val)%16))
#define DEC_2_HEX(val) (((val)/10)*16+((val)%10))
typedef struct
{
unsigned char second;
unsigned char minute;
unsigned char hour;
unsigned char weekday;
unsigned char day;
unsigned char month;
unsigned char year;
}
raw_data_t;
void rtc_get(rtc_data_t* rtc_data)
{
raw_data_t raw_data;
i2c_polling_read(SENSOR_ADDRESS,0x00,sizeof(raw_data),(char*)&raw_data);
rtc_data->second = HEX_2_DEC(raw_data.second);
rtc_data->minute = HEX_2_DEC(raw_data.minute);
rtc_data->hour = HEX_2_DEC(raw_data.hour );
rtc_data->day = HEX_2_DEC(raw_data.day );
rtc_data->month = HEX_2_DEC(raw_data.month );
rtc_data->year = HEX_2_DEC(raw_data.year );
}
void rtc_set(rtc_data_t* rtc_data)
{
raw_data_t raw_data;
raw_data.second = DEC_2_HEX(rtc_data->second);
raw_data.minute = DEC_2_HEX(rtc_data->minute);
raw_data.hour = DEC_2_HEX(rtc_data->hour );
raw_data.day = DEC_2_HEX(rtc_data->day );
raw_data.month = DEC_2_HEX(rtc_data->month );
raw_data.year = DEC_2_HEX(rtc_data->year );
raw_data.weekday = RTC_Weekday_Monday; // or calculate the exact day
i2c_polling_write(SENSOR_ADDRESS,0x00,sizeof(raw_data),(char*)&raw_data);
}
In addition to the initialization of the I2C controller, you will also need to implement the read/write routines.
UPDATE:
-------
Given `rtc_data_t* rtc_data`, here is a Segger-GUI code for displaying `HH:MM:SS` on the LCD:
char text[16] = {0};
sprintf(text,"%.2u:%.2u:%.2u",rtc_data->hour,rtc_data->minute,rtc_data->second);
GUI_RECT gui_rect = {0,0,SCREEN_WIDTH-1,SCREEN_HEIGHT-1};
GUI_DispStringInRect(text,&gui_rect,GUI_TA_HCENTER|GUI_TA_VCENTER);
Of course, you will have to initialize the LCD controller itself...
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