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rtc_clk_cal() function
Measure RTC slow clock's period, based on main XTAL frequency This function will time out and return 0 if the time for the given number of cycles to be counted exceeds the expected time twice. This may happen if 32k XTAL is being calibrated, but the oscillator has not started up (due to incorrect loading capacitance, board design issue, or lack of 32 XTAL on board).
Syntax
Implemented in ![]()
rtc_time.c:129
Return value
average slow clock period in microseconds, Q13.19 fixed point format, or 0 if calibration has timed out
Notes
When 32k CLK is being calibrated, this function will check the accuracy of the clock. Since the xtal 32k or ext osc 32k is generally very stable, if the check fails, then consider this an invalid 32k clock and return 0. This check can filter some jamming signal.