1choice RTC_CLK_SRC 2 prompt "RTC clock source" 3 default RTC_CLK_SRC_INT_RC 4 help 5 Choose which clock is used as RTC clock source. 6 7 - "Internal 90kHz oscillator" option provides lowest deep sleep current 8 consumption, and does not require extra external components. However 9 frequency stability with respect to temperature is poor, so time may 10 drift in deep/light sleep modes. 11 - "External 32kHz crystal" provides better frequency stability, at the 12 expense of slightly higher (1uA) deep sleep current consumption. 13 - "External 32kHz oscillator" allows using 32kHz clock generated by an 14 external circuit. In this case, external clock signal must be connected 15 to 32K_XP pin. Amplitude should be <1.2V in case of sine wave signal, 16 and <1V in case of square wave signal. Common mode voltage should be 17 0.1 < Vcm < 0.5Vamp, where Vamp is the signal amplitude. 18 - "Internal 8MHz oscillator divided by 256" option results in higher 19 deep sleep current (by 5uA) but has better frequency stability than 20 the internal 90kHz oscillator. It does not require external components. 21 22 config RTC_CLK_SRC_INT_RC 23 bool "Internal 90kHz RC oscillator" 24 config RTC_CLK_SRC_EXT_CRYS 25 bool "External 32kHz crystal" 26 select ESP_SYSTEM_RTC_EXT_XTAL 27 config RTC_CLK_SRC_EXT_OSC 28 bool "External 32kHz oscillator at 32K_XN pin" 29 select ESP_SYSTEM_RTC_EXT_OSC 30 config RTC_CLK_SRC_INT_8MD256 31 bool "Internal 8MHz oscillator, divided by 256 (~32kHz)" 32endchoice 33 34config RTC_CLK_CAL_CYCLES 35 int "Number of cycles for RTC_SLOW_CLK calibration" 36 default 3000 if RTC_CLK_SRC_EXT_CRYS || RTC_CLK_SRC_EXT_OSC || RTC_CLK_SRC_INT_8MD256 37 default 576 if RTC_CLK_SRC_INT_RC 38 range 0 8190 if RTC_CLK_SRC_EXT_CRYS || RTC_CLK_SRC_EXT_OSC || RTC_CLK_SRC_INT_8MD256 39 range 0 32766 if RTC_CLK_SRC_INT_RC 40 help 41 When the startup code initializes RTC_SLOW_CLK, it can perform 42 calibration by comparing the RTC_SLOW_CLK frequency with main XTAL 43 frequency. This option sets the number of RTC_SLOW_CLK cycles measured 44 by the calibration routine. Higher numbers increase calibration 45 precision, which may be important for applications which spend a lot of 46 time in deep sleep. Lower numbers reduce startup time. 47 48 When this option is set to 0, clock calibration will not be performed at 49 startup, and approximate clock frequencies will be assumed: 50 51 - 90000 Hz if internal RC oscillator is used as clock source. For this use value 1024. 52 - 32768 Hz if the 32k crystal oscillator is used. For this use value 3000 or more. 53 In case more value will help improve the definition of the launch of the crystal. 54 If the crystal could not start, it will be switched to internal RC. 55 56config RTC_XTAL_CAL_RETRY 57 int "Number of attempts to repeat 32k XTAL calibration" 58 default 3 59 depends on RTC_CLK_SRC_EXT_CRYS 60 help 61 Number of attempts to repeat 32k XTAL calibration 62 before giving up and switching to the internal RC. 63 Increase this option if the 32k crystal oscillator 64 does not start and switches to internal RC. 65