pub fn rtc_calib_init_code(_unit: u8, atten: Attenuation) -> Option<u16> {
        let version = Self::rtc_calib_version();

        if version != 1 {
            return None;
        }

        // See <https://github.com/espressif/esp-idf/blob/903af13e8/components/efuse/esp32c3/esp_efuse_table.csv#L176-L179>
        let init_code: u16 = Self::read_field_le(match atten {
            Attenuation::_0dB => ADC1_INIT_CODE_ATTEN0,
            Attenuation::_2p5dB => ADC1_INIT_CODE_ATTEN1,
            Attenuation::_6dB => ADC1_INIT_CODE_ATTEN2,
            Attenuation::_11dB => ADC1_INIT_CODE_ATTEN3,
        });

        Some(init_code + 1000) // version 1 logic
    }
Get ADC initial code for specified attenuation from efuse

see <https://github.com/espressif/esp-idf/blob/903af13e8/components/efuse/esp32c3/esp_efuse_rtc_calib.c#L25>
esp-hal/src/soc/esp32c3/efuse/mod.rs