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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/library/pyb.RTC.rst | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/docs/library/pyb.RTC.rst b/docs/library/pyb.RTC.rst index eeefa100ce..cd4b28eabd 100644 --- a/docs/library/pyb.RTC.rst +++ b/docs/library/pyb.RTC.rst @@ -57,3 +57,19 @@ Methods start up. - Bit 0x10000 is set if a power-on reset occurred. - Bit 0x20000 is set if an external reset occurred + +.. method:: rtc.calibration(cal) + + Get or set RTC calibration. + + With no arguments, ``calibration()`` returns the current calibration + value, which is an integer in the range [-511 : 512]. With one + argument it sets the RTC calibration. + + The RTC Smooth Calibration mechanism addjusts the RTC clock rate by + adding or subtracting the given number of ticks from the 32768 Hz + clock over a 32 second period (corresponding to 2^20 clock ticks.) + Each tick added will speed up the clock by 1 part in 2^20, or 0.954 + ppm; likewise the RTC clock it slowed by negative values. The + usable calibration range is: + (-511 * 0.954) ~= -487.5 ppm up to (512 * 0.954) ~= 488.5 ppm |