Improve adjtime() functionality #10827
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Based on the samv7 implementation, adjusts systick period.
1) Previously adjustments less than 1 microsecond per tick would be completely ignored. Now they are applied over a shorter period at a rate of 1 us per tick. 2) Previously CLOCK_ADJTIME_PERIOD was in units of 1/100th of second. Change to milliseconds to be more generally useful unit. Change setting name to CLOCK_ADJTIME_PERIOD_MS to make the unit change easier to notice. 3) Previously CLOCK_ADJTIME_SLEWLIMIT was in percentage. Most clock crystals have better accuracy than 1%, so the minimum slew rate was excessive. Change to CLOCK_ADJTIME_SLEWLIMIT_PPM with setting value in parts per million. 4) No need to use floating point math in clock_adjtime.c.
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xiaoxiang781216
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Summary
Prior pull request #9084 and issue #8858 added basic adjtime() support for the SAMv7 platform.
This pull request adds support for STM32 platform.
In addition I have made a few changes to the adjtime() configuration options:
Impact
Users who have used
CLOCK_ADJTIME_PERIODandCLOCK_ADJTIME_SLEWLIMITsettings should update their configuration. NewCLOCK_ADJTIME_PERIOD_MSis 10x the old period value, and newCLOCK_ADJTIME_SLEWLIMIT_PPMis 10000 times the old slewlimit.Testing
Tested on custom STM32 board with the
adjtimeexample program.Questions
@michallenc I couldn't find the significance of the
Should be between 0.95 and 0.99.comment that was previously in help text forCLOCK_ADJTIME_PERIOD. To me it appears that the desirable value for this setting will depend entirely on what code will be callingadjtime()and how often.