M5Stamp PLC Controller with M5StampS3 cannot write and read current Date and Time

[MCU1536]

Hi,

When M5Stamp PLC Controller with M5StampS3 got the power supply.
It can write and read the current Date and Time.
But after I turned of the power supply for 1 day.

The PLC shown "Sunday, 0 Jan 2090 33:20:39"
It is not the current Date and Time.

Could you recommend me to solve this?

Thank you

[robski]

This post is deleted!

[felmue]

Hello @MCU1536

assuming you are using Arduino and the M5StamPLC library then it is clear as to why the date and time are not retained. There is no code in the M5StamPLC library to enable charging the RTC backup battery.

I created a PR which enables RTC backup battery charging.

Thanks
Felix

[MCU1536]

Hello felmue,

After downloaded it and unzipped.
I copied 3 files as below and then replace them.

1. M5StamPLC.cpp at C:\Users\xxx\Documents\Arduino\libraries\M5StamPLC\src
2. rx8130.cpp at C:\Users\xxx\Documents\Arduino\libraries\M5StamPLC\src\utils\rx8130
3. rx8130.h at C:\Users\xxx\Documents\Arduino\libraries\M5StamPLC\src\utils\rx8130

It works well.
Thank you very much for your help.

[MCU1536]

Hello felmue,

When PLC was disconnected the power supply.
time.tm_wday cannot remember. Other are correct.

But PLC got the power supply.
It worked normally as below code.

---

char Text[100];
static struct tm time;
char DayOfWeek[7][10] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
char MonthOfYear[12][4] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};

sprintf(Text, "%s, %d %s %d %02d:%02d:%02d",
DayOfWeek[time.tm_wday],
time.tm_mday,
MonthOfYear[time.tm_mon],
time.tm_year + 1902,
time.tm_hour,
time.tm_min,
time.tm_sec);

Serial.print(Text);

---

Result

Wednesday, 19 Nov 2025 16:38:35

Thank you