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38 lines
1.7 KiB
Plaintext
38 lines
1.7 KiB
Plaintext
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choice RTC_CLK_SRC
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prompt "RTC clock source"
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default RTC_CLK_SRC_INT_RC32K
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help
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Choose which clock is used as RTC clock source.
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config RTC_CLK_SRC_EXT_CRYS
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bool "External 32kHz crystal"
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select ESP_SYSTEM_RTC_EXT_XTAL
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config RTC_CLK_SRC_EXT_OSC
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bool "External 32kHz oscillator at 32K_XP pin"
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select ESP_SYSTEM_RTC_EXT_OSC
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config RTC_CLK_SRC_INT_RC32K
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bool "Internal 32kHz RC oscillator"
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endchoice
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config RTC_CLK_CAL_CYCLES
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int "Number of cycles for RTC_SLOW_CLK calibration"
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default 3000 if RTC_CLK_SRC_EXT_CRYS || RTC_CLK_SRC_EXT_OSC || RTC_CLK_SRC_INT_RC32K
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default 1024 if RTC_CLK_SRC_INT_RC
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range 0 27000 if RTC_CLK_SRC_EXT_CRYS || RTC_CLK_SRC_EXT_OSC || RTC_CLK_SRC_INT_RC32K
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range 0 32766 if RTC_CLK_SRC_INT_RC
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help
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When the startup code initializes RTC_SLOW_CLK, it can perform
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calibration by comparing the RTC_SLOW_CLK frequency with main XTAL
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frequency. This option sets the number of RTC_SLOW_CLK cycles measured
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by the calibration routine. Higher numbers increase calibration
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precision, which may be important for applications which spend a lot of
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time in deep sleep. Lower numbers reduce startup time.
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When this option is set to 0, clock calibration will not be performed at
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startup, and approximate clock frequencies will be assumed:
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- 136000 Hz if internal RC oscillator is used as clock source. For this use value 1024.
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- 32768 Hz if the 32k crystal oscillator is used. For this use value 3000 or more.
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In case more value will help improve the definition of the launch of the crystal.
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If the crystal could not start, it will be switched to internal RC.
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