feat(PeriphDrivers): MAX32657 clock calibration #1468
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| { | ||
| static const int CAL_MS = 10; | ||
| /* IPO_FREQ / ERTCOCC_FREQ, integer divide, rounded */ | ||
| static const int AUTOCAL2_DIV = (IPO_FREQ + (ERTCO_FREQ - 1)) / ERTCO_FREQ; |
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This comes out to 1526 if my math is correct, should it not be 3662? Even if 1526 was left shifted it would come out to 3052.
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3662 and 3051 are based on different IPO frequencies. There is a typo in the documentation. 1526 = 50 MHz / 32768
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| /* Leaving the calibration hardware running will result in a more accurate frequency on average. | ||
| * Trim trim settings will oscillate around the ideal frequency. | ||
| */ | ||
| MXC_FCR->autocal0 &= ~(MXC_F_FCR_AUTOCAL0_RUN); |
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Is there any scenario where we might want a one-shot calibration and then shutdown the hardware, e.g. for power efficiency? If we want to leave the calibration hardware running, then should at least be documented in the header file for consumers, IMHO.
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Clearing the run bit here makes this a one-shot calibration.
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Description
Add pin configuration for RTC square wave output. Use a frequency counter to verify the RTC frequency. Adjust the trim values to get samples within crystal ppm specification.
Add IPO calibration function. Optionally leave the calibration procedure running to center the frequency. Each LSB of the trim value will be ~160 kHz.
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