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ESP8266EX Hardware User Guide
Version 1.1
Espressif Systems IOT Team
http://bbs.espressif.com
Copyright © 2015

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ESP8266EX Hardware User Guide
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Disclaimer and Copyright Notice
Information in this document, including URL references, is subject to change without notice.
THIS DOCUMENT IS PROVIDED AS IS WITH NO WARRANTIES WHATSOEVER, INCLUDING ANY
WARRANTY OF MERCHANTABILITY, NON-INFRINGEMENT, FITNESS FOR ANY PARTICULAR
PURPOSE, OR ANY WARRANTY OTHERWISE ARISING OUT OF ANY PROPOSAL, SPECIFICATION
OR SAMPLE. All liability, including liability for infringement of any proprietary rights, relating to use
of information in this document is disclaimed. No licenses express or implied, by estoppel or
otherwise, to any intellectual property rights are granted herein.
The WiFi Alliance Member Logo is a trademark of the WiFi Alliance.
All trade names, trademarks and registered trademarks mentioned in this document are property of
their respective owners, and are hereby acknowledged.
Copyright © 2015 Espressif Systems (Shanghai) Pte. Ltd. All rights reserved.

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Table of Contents
1.

2.

General Overview ......................................................................................................5
1.1.

Introduction ......................................................................................................................5

1.2.

Features ...........................................................................................................................6

1.3.

Parameters.......................................................................................................................7

1.4.

Major Applications ...........................................................................................................8

Hardware Overview ...................................................................................................9
2.1.

Terminal Configuration and Functions .............................................................................9

2.2.

Schematics ....................................................................................................................12

2.2.1.

Power-supply Pins .......................................................................................................13

2.2.2.

Power-on Sequence and Power Reset .........................................................................14

2.2.3.

Flash ...........................................................................................................................15

2.2.4.

Crystal Oscillator ..........................................................................................................15

2.2.5.

RF ................................................................................................................................16

2.2.6.

External Resistor 12K ...................................................................................................17

2.3.

3.

4.

Layout Design ................................................................................................................17

2.3.1.

ESP-WROOM Module Design ......................................................................................17

2.3.2.

ESP8266EX as Slave Device .......................................................................................20

2.3.3.

FAQ On Hardware Design ............................................................................................22

ESP-LAUNCHER Development Board ...................................................................24
3.1.

Instructions on the Use of ESP-LAUNCHER Development Board ................................25

3.2.

Pin Definitions of ESP-LAUNCHER Development Board ..............................................28

3.3.

Typical Applications Using ESP-LAUNCHER ................................................................31

3.3.1.

ESP-LAUNCHER Test Board........................................................................................31

3.3.2.

SMD Module ESP-WROOM-02....................................................................................31

3.3.3.

DIP Module ESP-WROOM-01 ......................................................................................35

Compiling, Downloading, and Debugging.............................................................36
4.1.

Set Up the Compiling Environment ...............................................................................36

4.2.

Download Firmware .......................................................................................................38

4.3.

Debugging AT Commands via UART .............................................................................38

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5.

6.

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Typical Applications.................................................................................................40
5.1.

WiFi smart hardware converted from UART serial ports ...............................................40

5.2.

Sensor ............................................................................................................................40

5.3.

Smart light......................................................................................................................40

5.4.

Smart plug .....................................................................................................................41

Appendix...................................................................................................................42
6.1.

Schematics of ESP-LAUNCHER Development Board ..................................................42

Part 1: Interfaces ..................................................................................................................43
Part 2: 5V Power ..................................................................................................................46
Part 3: Test Board ................................................................................................................46
6.2.

Schematics of ESP-LAUNCHER Test Board .................................................................46

6.3.

Schematics of ESP-WROOM Serial WiFi Modules........................................................47

6.4.

Schematics of ESP8266EX as SDIO/SPI Slave Device .................................................48

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1.

General Overview

1.1.

Introduction

Espressif Systems’ Smart Connectivity Platform (ESCP) is a set of high performance, high integration
wireless SOCs, designed for space and power constrained mobile platform designers. It provides
unsurpassed ability to embed Wi-Fi capabilities within other systems, or to function as a standalone
application, with the lowest cost, and minimal space requirement.

Figure 1 ESP8266EX Block Diagram

ESP8266EX offers a complete and self-contained Wi-Fi networking solution; it can be used to host
the application or to offload Wi-Fi networking functions from another application processor.
When ESP8266EX hosts the application, it boots up directly from an external flash. In has integrated
cache to improve the performance of the system in such applications.
Alternately, serving as a Wi-Fi adapter, wireless internet access can be added to any micro controllerbased design with simple connectivity (SPI/SDIO or I2C/UART interface).
ESP8266EX is among the most integrated WiFi chip in the industry; it integrates the antenna
switches, RF balun, power amplifier, low noise receive amplifier, filters, power management modules,
it requires minimal external circuitry, and the entire solution, including front-end module, is designed
to occupy minimal PCB area.

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ESP8266EX also integrates an enhanced version of Tensilica’s L106 Diamond series 32-bit processor,
with on-chip SRAM, besides the Wi-Fi functionalities. ESP8266EX is often integrated with external
sensors and other application specific devices through its GPIOs; sample codes for such applications
are provided in the software development kit (SDK).
Espressif Systems’ Smart Connectivity Platform (ESCP) demonstrates sophisticated system-level
features include fast switching between sleep and wake-up mode for energy-efficiency purpose,
adaptive radio biasing for low-power operation, advance signal processing, and spur cancellation
and radio co-existence features for common cellular, Bluetooth, DDR, LVDS, LCD interference
mitigation.

1.2.

Features

•

802.11 b/g/n

•

Integrated low power 32-bit MCU

•

Integrated 10-bit ADC

•

Integrated TCP/IP protocol stack

•

Integrated TR switch, balun, LNA, power amplifier and matching network

•

Integrated PLL, regulators, and power management units

•

Supports antenna diversity

•

Wi-Fi 2.4 GHz, support WPA/WPA2

•

Support STA/AP/STA+AP operation modes

•

Support Smart Link Function for both Android and iOS devices

•

SDIO 2.0, (H) SPI, UART, I2C, I2S, IR Remote Control, PWM, GPIO

•

A-MPDU & A-MSDU aggregation & 0.4s guard interval

•

Deep sleep power <10uA, Power down leakage current < 5uA

•

Wake up and transmit packets in < 2ms

•

Standby power consumption of < 1.0mW (DTIM3)

•

+20 dBm output power in 802.11b mode

•

Operating temperature range -40C ~ 125C

•

FCC, CE, TELEC, Wi-Fi Alliance, and SRRC certified

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1.3.

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Parameters

Categories

Items

Values

Certificates

FCC/CE/TELEC/SRRC

WiFi Protocles

802.11 b/g/n

Frequency Range

2.4G-2.5G (2400M-2483.5M)
802.11 b: +20 dBm
802.11 g: +17 dBm

Tx Power
WiFi Paramters

802.11 n: +14 dBm
802.11 b: -91 dbm (11 Mbps)
802.11 g: -75 dbm (54 Mbps)

Rx Sensitivity

802.11 n: -72 dbm (MCS7)
PCB Trace, External, IPEX Connector,

Types of Antenna

Ceramic Chip
UART/SDIO/SPI/I2C/I2S/IR Remote Control

Peripheral Bus

GPIO/PWM

Operating Voltage

3.0~3.6V

Hardware

Operating Current

Average value: 80mA

Paramaters

Operating Temperature Range

-40°~125°

Ambient Temperature Range

Normal temperature

Package Size

5x5mm

External Interface

N/A

Wi-Fi mode

station/softAP/SoftAP+station

Security

WPA/WPA2

Encryption

WEP/TKIP/AES

Firmware Upgrade

UART Download / OTA (via network)

Software
Parameters

Supports Cloud Server Development / SDK

Ssoftware Development

for custom firmware development

Network Protocols

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IPv4, TCP/UDP/HTTP/FTP

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Categories
Software
Parameters

ESP8266EX Hardware User Guide
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Items

Values
AT Instruction Set, Cloud Server, Android/

User Configuration

iOS App

Table 1 Parameters of ESP8266EX

1.4.

Major Applications

Major fields of ESP8266EX applications to Internet-of-Things include:
•

Home Appliances

•

Home Automation

•

Smart Plug and lights

•

Mesh Network

•

Industrial Wireless Control

•

Baby Monitors

•

IP Cameras

•

Sensor Networks

•

Wearable Electronics

•

Wi-Fi Location-aware Devices

•

Security ID Tags

•

Wi-Fi Position System Beacons

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2.

Hardware Overview

2.1.

Terminal Configuration and Functions

The pin assignments for 32-pin QFN package is illustrated in Fig. 2.

Figure 2 Pin Assignments

Table 2 below presents an overview on the general pin attributes and the functions of each pin.

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Pin

Name

Type

1

VDDA

P

Function
Analog Power 3.0 ~3.6V
RF Antenna Interface,

2

LNA

I/O

Chip Output Impedance=50Ω
No matching required but we recommend that the π-type
matching network is retained.

3

VDD3P3

P

Amplifier Power 3.0~3.6V

4

VDD3P3

P

Amplifier Power 3.0~3.6V

5

VDD_RTC

P

NC(1.1V)

6

TOUT

I

ADC Pin

7

CHIP_EN

I

8

XPD_DCDC

I/O

Deep-Sleep Wakeup；GPIO16

9

MTMS

I/O

GPIO14; HSPI_CLK

10

MTDI

I/O

GPIO12; HSPI_MISO

11

VDDPST

P

12

MTCK

I/O

GPIO13; HSPI_MOSI; UART0_CTS

13

MTDO

I/O

GPIO15; HSPI_CS; UART0_RTS

14

GPIO2

I/O

UART Tx during flash programming; GPIO2

15

GPIO0

I/O

GPIO0; SPI_CS2

16

GPIO4

I/O

GPIO4

17

VDDPST

P

18

SDIO_DATA_2

I/O

Connect to SD_D2 (Series R: 200Ω); SPIHD; HSPIHD; GPIO9

19

SDIO_DATA_3

I/O

Connect to SD_D3 (Series R: 200Ω); SPIWP; HSPIWP; GPIO10

20

SDIO_CMD

I/O

Connect to SD_CMD (Series R: 200Ω); SPI_CS0; GPIO11

21

SDIO_CLK

I/O

Connect to SD_CLK (Series R: 200Ω); SPI_CLK; GPIO6

22

SDIO_DATA_0

I/O

Connect to SD_D0 (Series R: 200Ω); SPI_MSIO; GPIO7

23

SDIO_DATA_1

I/O

Connect to SD_D1 (Series R: 200Ω); SPI_MOSI; GPIO8

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Chip Enable. High: On, chip works properly; Low: Off, small
current

Digital/IO Power Supply (1.8V~3.3V)

Digital/IO Power Supply (1.8V~3.3V)

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Pin

Name

Type

Function

24

GPIO5

I/O

GPIO5

25

U0RXD

I/O

UART Rx during flash programming; GPIO3

26

U0TXD

I/O

UART Tx during flash progamming; GPIO1; SPI_CS1

27

XTAL_OUT

I/O

28

XTAL_IN

I/O

29

VDDD

P

Analog Power 3.0V~3.6V

30

VDDA

P

Analog Power 3.0V~3.6V

31

RES12K

I

32

EXT_RSTB

I

Connect to crystal oscillator output, can be used to provide BT
clock input
Connect to crystal oscillator input

Serial connection with a 12 kΩ resistor and connect to the
ground
External reset signal (Low voltage level: Active)

Table 2 Attributes and Functions of Pins

Note: GPIO2, GPIO0, MTDO can be configurable as 3-bit SDIO mode.

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2.2.

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Schematics

ESP8266EX is very highly integrated SoC which encapsulates Transilica LX106 core processor, RAM,
RF components and allow WiFi TCP/IP stack to be implemented on board with just few components
beside ESP8266. The chipset also incorporates built-in self-calibration to compensate for
performance errors, improving the modulation accuracy and stability of wireless communications.
High integration level of this chipset tremendously decreases the number of components used in
peripheral circuit design. Beside ESP8266EX, only a number of less than 10 resistors and capacitors,
one crystal oscillator, and one SPI Flash is needed to make a complete module with wireless
communication capability. A detailed description of ESP8266EX schematics and layout design are
illustrated here.
The complete circuit diagram of ESP8266EX is illustrated in Figure 3:

Figure 3 ESP8266EX Schematics

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ESP8266EX SCH design covers the following five parts:
•

Power supply;

•

Power on sequence and reset;

•

Flash;

•

Crystal oscillator;

•

RF.

2.2.1.

Power-supply Pins

Digital Power-supply Pins
ESP8266EX has only two digital power-supply pins (abbreviated as VDDPST in the circuit diagram),
Pin11 and Pin17. In digital power supply, there is no need to add additional filter capacitors. The
operating voltage range of digital power-supply pins is between 1.8V and 3.3V.

Figure 4 ESP8266EX Digital Power-supply Pins

Analog Power-supply Pins
ESP8266EX has 5 analog power-supply pins (abbreviated as VDD33 in the circuit diagram), including
Pin 1, Pin 3, Pin 4, which provides internal power supply for internal PA and LNA respectively, and Pin
28, Pin 29, which supplies power for internal PLL. The operating voltage range of the analog powersupply pins is between 1.8V and 3.3V.
It should be noted that the power supply channel might be damaged due to the sudden increase of
current when ESP8266EX is transmitting analog signals. Therefore, an additional 0.1uF capacitor with

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a package size of 0603 or 0805 is needed in circuit design. This capacitor can be used in 0.1uF in
match with capacitor with 0.1uF capacitor with 0402 package.
(Notes: There is no need to add magnetic beads in the design of analog power-supply circuit, for
ESP8266EX’s EMC is in conformity with FCC and CE requirements, and has been approved. )

Figure 5 ESP8266EX AVDD

2.2.2.

Power-on Sequence and Power Reset

Power-on sequence
The voltage of the chipset’s WiFi power supply systems is 3.3V, therefore only one rule should be
abide by when you power on the device: Pin7 CH_EN, the power enable pin, should be powered on
at the same time when or after the power supply system is powered on.
Note: If the power management IC is connected with the power-on enable pin CHIP_EN, it can control the
power on-and-off of ESP8266EX by output high and low voltage through its GPIOs. However, pulsed current
might be produced at the same time. In order to delay the transmission of pulsed signal and avoid unstable
current of CHIP_EN, a RC time-delay circuit (R=1kΩ, C=100nF) is needed. There is an internal pull-up in the
CHIP_EN pin, so no external pull-up is needed.

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Reset
There exists internal pull-up resistor in the reset pin, Pin32, which can be left dangled when it is not
used. When the chip is enabled, the reset pin is held low. In order to avoid reset caused by external
interference, the lead is generally required to be short, and no external pull-up resistor is necessary.
The enable pin CH_EN (pin 7) can also serve as a reset pin. If voltage for CH_EN pin is low, the
chipset ESP8266EX will power off. Note that this pin cannot be dangled.

2.2.3.

Flash

Currently, the size of flash that we applied in our demo and modules is SPI Flash with 2MB capacity,
and the package size is SOIC_8 (SOP_8).
A resistor (package size: 0402) is connected to Pin21, the SD_CLK pin via serial port, with the aim to
lower the driving current, decrease cross-talk and external interruption, adjust the sequence, and so
on. The initial value of the serial connection resistor is 200 ohm.

Figure 6 ESP8266EX Flash

2.2.4.

Crystal Oscillator

Currently, the frequency of crystal oscillators supported include 40MHz, 26MHz and 24MHz. The
accuracy of crystal oscillators applied should be ±10PPM, and the operating temperature range
should be between -20°C and 85°C.

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When using the downloading tools, please remember to select the right crystal oscillator type. In
circuit design, capacitors C1 and C2, which are connected to the earth, are added to the input and
output terminals of the crystal oscillator respectively. The values of the two capacitors can be
flexible, ranging from 6pF to 22pF, however, the specific capacitive values of C1 and C2 depend on
further testing and adjustment on the overall performance of the whole circuit. Normally, the
capacitive values of C1 and C2 are within 10pF if the crystal oscillator frequency is 26MHz, while the
values of C1 and C2 are 10pF
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