measure RTC crystal freqeuncy against MCU crystal

Dependencies:   mbed

This program uses the RTC 1-second interrupt to capture the Timer microsecond value to estimate the error in the RTC's 32KHz crystal. (the K64F MCU's crystal could be in error as well, though mine was within 20 ppm). This program measured the error at about 250 ppm, well out of the 20ppm spec for the RTC crystal???

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Files at revision 0:b30b04f4a2aa

Name Size Actions
main.cpp 785 Revisions Annotate
mbed.bld 65 Revisions Annotate