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8ccb2a4990
Small changes to clock calibration value will cause increasing errors
the longer the device runs. Consider the case of deep sleep, assuming
that RTC counter is used for timekeeping:
- before sleep:
time_before = rtc_counter * calibration_val
- after sleep:
time_after = (rtc_counter + sleep_count) * (calibration_val + epsilon)
where 'epsilon' is a small estimation error of 'calibration_val'.
The apparent sleep duration thus will be:
time_after - time_before = sleep_count * (calibration_val + epsilon)
+ rtc_counter * epsilon
Second term on the right hand side is the error in time difference
estimation, it is proportional to the total system runtime (rtc_counter).
To avoid this issue, this change makes RTC_SLOW_CLK calibration value
persistent across restarts. This allows the calibration value update to
be preformed, while keeping time after update same as before the update.
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| .. | ||
| aes.h | ||
| bigint.h | ||
| cache.h | ||
| crc.h | ||
| efuse.h | ||
| ets_sys.h | ||
| gpio.h | ||
| libc_stubs.h | ||
| lldesc.h | ||
| md5_hash.h | ||
| miniz.h | ||
| queue.h | ||
| rtc.h | ||
| secure_boot.h | ||
| sha.h | ||
| spi_flash.h | ||
| tbconsole.h | ||
| tjpgd.h | ||
| uart.h | ||