Patch to support optional use of the Pico RTC for filesystem timestamps

[xoblite]

Hi all,

I can't issue a proper pull request at the moment, but it's a really simple patch for tf_card.c so I'll just put it here for now:

DWORD get_fattime (void)
{
	datetime_t t;
	if (rtc_get_datetime(&t))
	{
		return (((t.year - 1980) << 25) + (t.month << 21) + (t.day << 16) + (t.hour << 11) + (t.min << 5) + (t.sec >> 1));
	}
	else
	{
		// Quoting the FatFs documentation, see http://elm-chan.org/fsw/ff/doc/fattime.html :
		// "The get_fattime function shall return any valid time even if the system does not support
		// a real time clock. If a zero is returned, the file will not have a valid timestamp."
		return (((2024 - 1980) << 25) + (1 << 21) + (1 << 16)); // -> 2024, January 1, 00:00:00
	}
}

...plus the associated Pico SDK #include and target_link_library for hardware_rtc elsewhere of course.

Thanks,

BR//Karl @xoblite

[elehobica]

Hello @xoblite
Thank you for raising this.

Since get_fattime is defined with weak attribute, you can override it as you like without changing the library itself.

Following is an example that I did almost same thing. (Please focus at tf_card_override.c itself and ignore other parts)

https://github.com/elehobica/pico_spdif_recorder/blob/main/lib/pico_fatfs_customized/tf_card_override.c

Usually it should be okay to just put tf_card_override.c on your project local and compile.

I'm going to add guide on README.

Hope this helps you