tom dunigan / Mbed 2 deprecated driftrtc

LPC1768 RTC frequency check with WDT. Compare RTC against MCU's microsecond Timer.

Dependencies:   mbed

Check LPC1768 RTC crystal frequency using WDT. Measure with MCU's microsecond Timer. The MCU's crystal may be off a bit as well. I measured the RTC frequency error at 22 ppm. The spec for the RTC crystal is 20 ppm. Using NTP and a GPS, I had measured the MCU's crystal frequency error at -2 ppm.

Frequency measurements for other MCU/RTC cyrstals at

https://github.com/manitou48/crystals/blob/master/crystals.txt

History

LPC1768 RTC freq check with WDT default tip

2015-11-16, by manitou [Mon, 16 Nov 2015 16:56:32 +0000] rev 0

LPC1768 RTC freq check with WDT