esp-open-rtos/examples/fatfs_rtc/README.md

This example shows how to use real-time clock (e.g. ds1307) with FatFs for real timestamps on the filesystem objects.

1. Set FATFS_FS_NORTC to 0 (it's 1 by default) in application makefile.
2. Define function uint32_t get_fattime() which will return current time in timestamp format:

Bits	Date part
0..4	Second / 2 (0..29)
5..10	Minute (0..59)
11..15	Hour (0..23)
16..20	Day (1..31)
21..24	Month (1..12)
25..31	Year origin from 1980 (0..127)