Espressif Systems ESP32 Technical Reference Manual page 66

4.13 Registers
31 27 53
0 0 0
RTCIO_EXT_WAKEUP0_SEL GPIO[0-17] can be used to wake up the chip when the chip is in sleep
mode. This register selects the pad source to wake up the chip in deep/light sleep mode. 0: select
GPIO0; 1: select GPIO2, etc. (R/W)
31 27 53
0 0 0
RTCIO_XTL_EXT_CTR_SEL Select the external crystal power down enable source in sleep
mode. 0: select GPIO0; 1: select GPIO2, etc.
CIO_RTC_EXT_XTAL_CONF_REG[30] is the crystal power down enable signal. (R/W)
31 30 29 28 55
0 0 0 0 0
RTCIO_SAR_I2C_SDA_SEL Selects a different pad as the RTC I2C SDA signal.
TOUCH_PAD[1]; 1: use pad TOUCH_PAD[3]. (R/W)
RTCIO_SAR_I2C_SCL_SEL Selects a different pad as the RTC I2C SCL signal.
TOUCH_PAD[1]; 1: use pad TOUCH_PAD[3]. (R/W)
Espressif Systems
Register 4.54: RTCIO_EXT_WAKEUP0_REG (0x002f)
0 0 0 0 0 0 0 0
Register 4.55: RTCIO_XTL_EXT_CTR_REG (0x0030)
0 0 0 0 0 0 0 0
Register 4.56: RTCIO_SAR_I2C_IO_REG (0x0031)
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
The input value on this pin XOR RT-
0 0 0 0 0 0 0 0
65 ESP32 Technical Reference Manual V1.0
4 IO_MUX AND GPIO MATRIX
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0: use pad
0: use pad
27
0 Reset
27
0 Reset
28
0 Reset