diff --git a/components/esp32/Kconfig b/components/esp32/Kconfig index 545b99b4d..1540d4549 100644 --- a/components/esp32/Kconfig +++ b/components/esp32/Kconfig @@ -928,6 +928,16 @@ menu "ESP32-specific" In case more value will help improve the definition of the launch of the crystal. If the crystal could not start, it will be switched to internal RC. + config ESP32_RTC_XTAL_CAL_RETRY + int "Number of attempts to repeat 32k XTAL calibration" + default 1 + depends on ESP32_RTC_CLOCK_SOURCE_EXTERNAL_CRYSTAL + help + Number of attempts to repeat 32k XTAL calibration + before giving up and switching to the internal RC. + Increase this option if the 32k crystal oscillator + does not start and switches to internal RC. + config ESP32_RTC_XTAL_BOOTSTRAP_CYCLES int "Bootstrap cycles for external 32kHz crystal" depends on ESP32_RTC_CLOCK_SOURCE_EXTERNAL_CRYSTAL diff --git a/components/esp32/clk.c b/components/esp32/clk.c index c965511cb..096933bbc 100644 --- a/components/esp32/clk.c +++ b/components/esp32/clk.c @@ -40,8 +40,19 @@ */ #define SLOW_CLK_CAL_CYCLES CONFIG_ESP32_RTC_CLK_CAL_CYCLES +#ifdef CONFIG_ESP32_RTC_XTAL_CAL_RETRY +#define RTC_XTAL_CAL_RETRY CONFIG_ESP32_RTC_XTAL_CAL_RETRY +#else +#define RTC_XTAL_CAL_RETRY 1 +#endif + #define MHZ (1000000) +/* Lower threshold for a reasonably-looking calibration value for a 32k XTAL. + * The ideal value (assuming 32768 Hz frequency) is 1000000/32768*(2**19) = 16*10^6. + */ +#define MIN_32K_XTAL_CAL_VAL 15000000L + /* Indicates that this 32k oscillator gets input from external oscillator, rather * than a crystal. */ @@ -167,6 +178,11 @@ static void select_rtc_slow_clk(slow_clk_sel_t slow_clk) { rtc_slow_freq_t rtc_slow_freq = slow_clk & RTC_CNTL_ANA_CLK_RTC_SEL_V; uint32_t cal_val = 0; + /* number of times to repeat 32k XTAL calibration + * before giving up and switching to the internal RC + */ + int retry_32k_xtal = RTC_XTAL_CAL_RETRY; + do { if (rtc_slow_freq == RTC_SLOW_FREQ_32K_XTAL) { /* 32k XTAL oscillator needs to be enabled and running before it can @@ -185,7 +201,10 @@ static void select_rtc_slow_clk(slow_clk_sel_t slow_clk) // When SLOW_CLK_CAL_CYCLES is set to 0, clock calibration will not be performed at startup. if (SLOW_CLK_CAL_CYCLES > 0) { cal_val = rtc_clk_cal(RTC_CAL_32K_XTAL, SLOW_CLK_CAL_CYCLES); - if (cal_val == 0 || cal_val < 15000000L) { + if (cal_val == 0 || cal_val < MIN_32K_XTAL_CAL_VAL) { + if (retry_32k_xtal-- > 0) { + continue; + } ESP_EARLY_LOGW(TAG, "32 kHz XTAL not found, switching to internal 150 kHz oscillator"); rtc_slow_freq = RTC_SLOW_FREQ_RTC; }