ESP32 Forum

Hello,
I have an external RTC connected to the ESP32 via an i2c port. I want to use this time/date as the ESP32 time reference. I need to update the ESP32 time/date at boot with this external RTC value. I also have an sdcard interface and I want to be able to create a file and have that file time/date info match the RTC time/date. Currently I'm using POSIX commands such as fopen() and when a file or directory is created I get the default time/date which is something like 11:00pm, January 1, 1979. I know that I need to initialize the ESP32 time and date from the RTC at boot and have looked at the comments/examples on the web for this with no luck. Most of the info seems to be using an internet retreived time/date. My device only uses AP mode and I have no internet connection hence the need for the RTC.
Can any one provide an example of setting the time/date of the ESP32 based on the following strings(that I get from my i2c connected RTC chipset)
time: 14:48:22
date: 04/26/2022

I have the current time/date, just need to know how to initialize the ESP32 timer system with that value at boot so when a user creates a file on the sd card from a client connected device it will have the correct date.
Any help would be appreciated.
Thanks

You probably want to use settimeofday() to update the systems idea of the current time.

Ok, so if you need to set the ESP32 system time and date at boot from an RTC(connected to the serial port), here's a method that works. Runtime.hour, minute, second, etc. is updated by reading the RTC via serial commands before calling this routine. Hopes this helps.

void SetESP32SysTime(void)
{
struct tm tm;
char tmpcmd[TX_BUF_SIZE];

//Get current time from the RTC
memset(tmpcmd, '\0', TX_BUF_SIZE);
//Now put the command to get douts into the tx buffer
sprintf(&tmpcmd[0], "%s", "gtime\r");

//Ship out the command to the STM32
sendData(TX_TASK_TAG, tmpcmd);

//Wait 50ms for the response
vTaskDelay(50/portTICK_RATE_MS);
ESP_LOGI(TAG, "System time %d:%d:%d", Runtime.hour, Runtime.minute, Runtime.second);

//Get current date from the RTC
memset(tmpcmd, '\0', TX_BUF_SIZE);
//Now put the command to get douts into the tx buffer
sprintf(&tmpcmd[0], "%s", "gdate\r");

//Ship out the command to the STM32
sendData(TX_TASK_TAG, tmpcmd);

//Wait 50ms for the response
vTaskDelay(50/portTICK_RATE_MS);
ESP_LOGI(TAG, "System date %d/%d/%d", Runtime.month, Runtime.day, Runtime.year);

tm.tm_year = (Runtime.year + 2000) - 1900;
tm.tm_mon = Runtime.month - 1;
tm.tm_mday = Runtime.day;
tm.tm_hour = Runtime.hour;
tm.tm_min = Runtime.minute;
tm.tm_sec = Runtime.second;
time_t t = mktime(&tm);
ESP_LOGI(TAG, "Setting System Time: %s", asctime(&tm));
struct timeval now = { .tv_sec = t };
settimeofday(&now, NULL);
}

The year in this code is Runtime.year = 22 just to be clear.