I had already done this (cut the RESET-EN traces and soldered some wires back to the pads and other ends to a switch. However, I later discovered that my time reset problems stemmed from the code as there is code to program the RTC initially, and then certain language needs to be removed, commented out, or buried deep in some 'if' tests to resync it to something else. Here is a function that a friend shared with me and I was able to change it around to suit my project and RTC (DS1307 or DS3231). Because I also use Blynk with my project, the code has a lot of Blynk/Arduino language, but ultimately re-syncs my RTC every 5 minutes or so
Code: Select all
void syncRTCHardware()
{
char currentTime[16];
char currentDate[16];
sprintf(currentDate, "%02d/%02d/%04d", month(), day(), year());
sprintf(currentTime, "%02d:%02d:%02d", hour(), minute(), second());
Serial.print("Server Time: ");
Serial.print(currentDate);
Serial.print (" ");
Serial.println(currentTime);
DateTime now = RTC.now(); // reads time at beginning of loop
byte HOUR = now.hour();
byte twelveHour = now.hour() - 12; // Variable used to display 13+ hours in 12 hour format
byte zeroHour = 12; // Variable use to convert "0" zero hour to display it as 12:00+
byte displayHour;
byte MIN = now.minute();
byte SEC = now.second();
char* meridian;
if (now.hour() == 0) // First we test if the hour reads "0"
{
displayHour = zeroHour;
meridian = "AM";
}
else if (now.hour() >= 13) // if no, Second we test if the hour reads "13 or more"
{
displayHour = twelveHour;
meridian = "PM";
}
else
{
displayHour = now.hour();
meridian = "AM";
}
char stamp[16];
lcdA.clear();
sprintf(stamp, "%02d:%02d:%02d-%02s", displayHour, MIN, SEC, meridian);
lcdA.print(3, 0, stamp);
sprintf(stamp, "%02d/%02d/%04d", now.month(), now.day(), now.year());
lcdA.print(3, 1, stamp);
// time library is synchronized by the Blynk WidgetRTC
if (Blynk.connected())
{
if (now.hour() != hour() || now.minute() != minute() || now.second() != second())
{
Serial.println("Resynching RTC Time...");
terminal.println("Resynching RTC Time...");
RTC.adjust(DateTime(year(), month(), day(), hour(), minute(), second()));
terminal.flush();
}
}
}
BLYNK_CONNECTED()
{
rtcWidget.begin(); // Synchronize with widget (server) time on connection
setSyncInterval(5 * 60); // subsequent time sync interval in seconds (5 minutes)
}
. Despite careful soldering (and resoldering) and continuity testing, the RTC on the Mega resets when powering up (battery ok and onboard). I have only connected the GND, VCC, SDA, and SDL on the RTC to the matching pads right next to the prototyping area. It sits there very nicely - but it just resets after each power down/up. No other modules attached, only running the bog standard TestRTC sketch, which clean compiles and uploads. I can then set TIME and DATE (although TEMP says "temp not available"). TIME and DATE continue to tick over and are accessible and update properly, until I power off the board. Restart a minute later and the time and date are back to 09:00:00. 
