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https://github.com/espressif/esp-idf.git
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66 lines
3.3 KiB
Plaintext
66 lines
3.3 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_RC
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help
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Choose which clock is used as RTC clock source.
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- "Internal 90kHz oscillator" option provides lowest deep sleep current
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consumption, and does not require extra external components. However
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frequency stability with respect to temperature is poor, so time may
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drift in deep/light sleep modes.
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- "External 32kHz crystal" provides better frequency stability, at the
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expense of slightly higher (1uA) deep sleep current consumption.
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- "External 32kHz oscillator" allows using 32kHz clock generated by an
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external circuit. In this case, external clock signal must be connected
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to 32K_XN pin. Amplitude should be <1.2V in case of sine wave signal,
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and <1V in case of square wave signal. Common mode voltage should be
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0.1 < Vcm < 0.5Vamp, where Vamp is the signal amplitude.
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Additionally, 1nF capacitor must be connected between 32K_XP pin and
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ground. 32K_XP pin can not be used as a GPIO in this case.
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- "Internal 8MHz oscillator divided by 256" option results in higher
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deep sleep current (by 5uA) but has better frequency stability than
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the internal 90kHz oscillator. It does not require external components.
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config RTC_CLK_SRC_INT_RC
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bool "Internal 90kHz RC oscillator"
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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_XN pin"
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select ESP_SYSTEM_RTC_EXT_OSC
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config RTC_CLK_SRC_INT_8MD256
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bool "Internal 8MHz oscillator, divided by 256 (~32kHz)"
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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_8MD256
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default 576 if RTC_CLK_SRC_INT_RC
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range 0 125000
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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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- 90000 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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config RTC_XTAL_CAL_RETRY
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int "Number of attempts to repeat 32k XTAL calibration"
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default 3
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depends on RTC_CLK_SRC_EXT_CRYS
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help
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Number of attempts to repeat 32k XTAL calibration
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before giving up and switching to the internal RC.
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Increase this option if the 32k crystal oscillator
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does not start and switches to internal RC.
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