ESP32 32kHz晶振为什么无法找到？

问题如下：最近外挂了一个外部32kHz晶振，sdkconfig中宏定义：#define CONFIG_BTDM_LPCLK_SEL_EXT_32K_XTAL 1

bt.c 部分代码如下：
#if CONFIG_BTDM_LPCLK_SEL_EXT_32K_XTAL
    // check whether or not EXT_CRYS is working
    if (rtc_clk_slow_freq_get() == RTC_SLOW_FREQ_32K_XTAL) {
        btdm_lpclk_sel = BTDM_LPCLK_SEL_XTAL32K; // set default value
#ifdef CONFIG_PM_ENABLE
        s_btdm_allow_light_sleep = true;
#endif
    } else {
        ESP_LOGW(BTDM_LOG_TAG, "32.768kHz XTAL not detected, fall back to main XTAL as Bluetooth sleep clockn"
                 "light sleep mode will not be able to apply when bluetooth is enabled");
        btdm_lpclk_sel = BTDM_LPCLK_SEL_XTAL; // set default value
    }

开机logo如下：
[14:42:52.219]收←◆[0;33mW (1826) clk: 32 kHz XTAL not found, switching to internal 150 kHz oscillator[0m

[14:42:52.361]收←◆[0;31mE (2090) DBY?[0;33mW (2095) BTDM_INIT: 32.768kHz XTAL not detected, fall back to main XTAL as Bluetooth sleep clock
light sleep mode will not be able to apply when bluetooth is enabled[0m

为什么找不到32kHz的晶振，我还需要做什么另外的操作吗？外挂晶振电路图是按照硬件指导做的。