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Using a Stm32f078 controller, I want to achieve accuracy in RTC.

How to implement the RTC synchronisation in code or digital smooth calibration?

I don't want to use any external signal source.

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  • \$\begingroup\$ Define "accuracy" \$\endgroup\$ – Ron Beyer Mar 18 '20 at 14:15
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    \$\begingroup\$ What would you calibrate it against, if not an external signal? I'm a bit confused. \$\endgroup\$ – Marcus Müller Mar 18 '20 at 14:29
  • \$\begingroup\$ Do you at least have an HSE crystal? Without any crystals, the best you can reasonably do is a few percent accuracy, using the HSI oscillator. Needless to say, that's completely useless for any sort of timekeeping (order of magnitude of error: 1 second/minute). \$\endgroup\$ – swineone Mar 18 '20 at 14:42
  • \$\begingroup\$ There is an application note from ST which explains the calibration process. It always includes an external refernece. Only the counting of the clock can be done externally or uC internally by using a clock module (like it is done in the example code from ST). \$\endgroup\$ – A.R.C. Mar 19 '20 at 13:47

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