1

GND

(Pin 1 is in the corner close to the xtal and away from antenna)

2

NC

3

UTXD

SPICS1, GPIO1, CLK_RTC

Typically used as serial uart0 TX

4

URXD

I2SO_DATA, GPIO3, CLK_XTAL

Typically used as serial uart0 RX

5

GPIO16

XPD_DCDC, RTC_GPIO0, EXT_WAKEUP, DEEPSLEEP

Connected to XPD_DCDC ESP pin, can also be connected to ESP EXT_RSTB (reset) pin by closing jumper near pin 8; Reset pin is active low and has an internal weak pull-up; Connecting jumper is required to wake-up ESP from deep-sleep: RTC produces pulse on XPD_DCDC pin that needs to be fed into EXT_RSTB pin

6

CH_PD

Power-down: low input powers down chip, high powers up; tie high for normal operation or module will not function

7

ANT

Wifi Antenna, do not connect

8

VCC

3.3V input (pin 8 is between antenna and ESP chip)

9

GPIO14

MTMS, I2SI_WS, SP_CLK

10

GPIO12

MTDI, I2SI_DATA, MISO

11

GPIO13

MTCK, I2SI_BCK, MOSI

12

GPIO15

MTDO, I2SO_BCK, SP_CS

At boot: must be low to enter flash or normal boot (high enters special boot modes)

13

GPIO2

I2SO_WS, U1TXD, U0TXD

At boot: must be high to enter flash or normal boot (low enters special boot modes); Typically is used as uart1 TX for debug logging

14

GPIO0

SPICS2, CLK_OUT

At boot: low causes bootloader to enter flash upload mode; high causes normal boot