RTC is inaccurate

[joebirch]

The RTC is about .02% off (11 secs after 15hrs)

I am using the KSDK2.0 rtc_func demo ("C:\Freescale\KSDK_2.0\boards\frdmk22f\demo_apps\rtc_func").

I have tried it on 2 different FRDM-K22F eval boards

Board 1: 11 secs fast after 15.5 hrs

Board 2: 7 secs after 15hrs,  22 secs after 40hrs

The FRDM-K22F BOM shows the osc is 20PPM

Am I doing something wrong?

I know the RTC can be adjusted but it is unacceptable to have to customize this for each board.

Please help

Joe

[ivadorazinova]

Hi joe birch​,

please use external clk for RTC because internal oscillator is not very accurate.

You can trim accuracy by using external capacitors.

I hope this helps you.

Have a nice day.

Iva

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[joebirch · Accepted solution]

Iva

I am using the FRDM-K22 board and the the KSDK2.0 rtc_func demo ("C:\Freescale\KSDK_2.0\boards\frdmk22f\demo_apps\rtc_func").

This uses the eternal 32.768k osc.

But maybe the osc is not 20PPM as advertised.

I realize this is not a KSDK topic so I will mark this as corrected.

Thanks

Joe