Espressif Systems ESP8266EX Installation manual

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

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Espressif Systems
ESP8266EX Hardware User Guide
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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1. General Overview 5......................................................................................................
1.1. Introduction!5"......................................................................................................................
1.2. Features!6"...........................................................................................................................
1.3. Parameters!7".......................................................................................................................
1.4. Major Applications!8"...........................................................................................................
2. 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. 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............................................................................................
3. 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......................................................................................
4. 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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Table of Contents

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ESP8266EX Hardware User Guide
5. 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".....................................................................................................................
6. 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 controller-
based 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. Parameters
Categories
Items
Values
WiFi Paramters
Certificates
FCC/CE/TELEC/SRRC
WiFi Protocles
802.11 b/g/n
Frequency Range
2.4G-2.5G (2400M-2483.5M)
Tx Power
802.11 b: +20 dBm
802.11 g: +17 dBm
802.11 n: +14 dBm
Rx Sensitivity
802.11 b: -91 dbm (11 Mbps)
802.11 g: -75 dbm (54 Mbps)
802.11 n: -72 dbm (MCS7)
Types of Antenna
PCB Trace, External, IPEX Connector,
Ceramic Chip
Hardware
Paramaters
Peripheral Bus
UART/SDIO/SPI/I2C/I2S/IR Remote Control
GPIO/PWM
Operating Voltage
3.0~3.6V
Operating Current
Average value: 80mA
Operating Temperature Range
-40°~125°
Ambient Temperature Range
Normal temperature
Package Size
5x5mm
External Interface
N/A
Software
Parameters
Wi-Fi mode
station/softAP/SoftAP+station
Security
WPA/WPA2
Encryption
WEP/TKIP/AES
Firmware Upgrade
UART Download / OTA (via network)
Ssoftware Development
Supports Cloud Server Development / SDK
for custom firmware development
Network Protocols
IPv4, TCP/UDP/HTTP/FTP
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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
Categories
Items
Values
Software
Parameters
User Configuration
AT Instruction Set, Cloud Server, Android/
iOS App
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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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ESP8266EX Hardware User Guide
Pin
Name
Type
Function
1
VDDA
P
Analog Power 3.0 ~3.6V
2
LNA
I/O
RF Antenna Interface,
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
Chip Enable. High: On, chip works properly; Low: Off, small
current
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
Digital/IO Power Supply (1.8V~3.3V)
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
Digital/IO Power Supply (1.8V~3.3V)
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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Table 2 Attributes and Functions of Pins
Note: GPIO2, GPIO0, MTDO can be configurable as 3-bit SDIO mode.
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
Connect to crystal oscillator output, can be used to provide BT
clock input
28
XTAL_IN
I/O
Connect to crystal oscillator input
29
VDDD
P
Analog Power 3.0V~3.6V
30
VDDA
P
Analog Power 3.0V~3.6V
31
RES12K
I
Serial connection with a 12 kΩresistor and connect to the
ground
32
EXT_RSTB
I
External reset signal (Low voltage level: Active)
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2.2. 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 power-
supply 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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ESP8266EX Hardware User Guide
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<C1, C2<22pF if the crystal oscillator frequency is 40MHz.
Figure 7 ESP8266EX Crystal oscillators
Note: Defects in the craftsmanship of the crystal oscillators (for example, high frequency deviation,
unstable working temperature) may lead to the malfunction of ESP8266EX, resulting in the decrease
of overall performance.
2.2.5. RF
The output impedance of RF pin (Pin 2) is 50 ohm. Normally, when the antenna impedance
approaches 50 ohm, antenna matching is not necessary. However, low-price antenna commercially
available in the market does not feature 50 ohm impedance. Besides, the impedance in 2.4G to 2.5G
frequency band is rather scattered. Therefore, N-type matching network is essential in circuit design
to facilitate antenna matching.!
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Figure 8 ESP8266EX RF
2.2.6. External Resistor 12K
An external resistor that is connected to the ground should be added to ERS12K pin (Pin31), so as to
control the bias current in the circuit. Therefore, relatively high resistance value accuracy is required,
an accuracy of 12K±1% is recommended.
Figure 9 External Resistor
2.3. Layout Design
PCB layout design of products using chipset ESP8266EX is demonstrated in this part. Hereto we
mainly focus on two kinds of designs, one is ESP-WROOM serial to WiFi modules, and the other is
main board mounted with ESP8266EX WiFi module.
2.3.1. ESP-WROOM Module Design
• Module layout design and the key techniques:
This printed circuit board has four layers.
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The first layer is the TOP layer, signal lines and components are placed on the top of the printed
circuit board;
The second layer is the GND layer, no signal lines is laid so as to ensure an entire plain GND plane;
The third layer is the POWER layer, only power lines can be placed on this layer. However, there is
exceptional cases. When there is no other choice but to place some signal lines on this layer, it is
acceptable.
The forth layer is the BOTTOM layer, only signal lines are designed on this layer, no components
shall be placed on this layer.
• On design of the power-supply part
The power supply voltage of those signal lines highlighted in yellow is 3.3V. The total width of the
power line shall be larger than 15 mil.
Before the power line reaches the analog power-supply pins (including Pin 1, 3, 4, 28, 29) of
ESP8266EX, a 10uF capacitor with 0603 or 0805 package needs to be added, as is illustrated in Fig.
10. C6, which is the capacitor, should be placed adjacent to the analog power-supply pins of the
chipset.
Power lines should be placed on the third layer. When the power lines reached the pins of the
chipset, VIAs are needed so that the power lines can go through the layers to connect the pins of the
chipset on the TOP layer. The diameter of the VIA holes should exceed the width of power lines,
while the drill should be appropriate, a little bit larger than the radius of VIA is enough.
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Figure 10 ESP8266EX PCB Layout
• On design of the crystal oscillator
Crystal oscillator should be placed adjacent to the XTAL Pins, the connection lines shouldn’t be too
long, and should be wrapped up for shelter.
The input and output lines cannot be punched, cannot cross the layers or be crossed.
The input and output bypass capacitor should be located near the chip; never set it on the lines.
No high frequency digital signal lines shall be placed under the four layers of the crystal oscillators.
The best choice is that no signal lines is placed under the crystal oscillator. The TOP layer where is
crystal oscillator is placed should be as large as possible.
Magnetic components, such as high current inductors, should not be placed near to crystal oscillator,
a sensitive component.
Figure 11 ESP8266EX Crystal Oscillators PCB Layout
• On design of the RF part
The characteristic impedance that RF lines should control is 50Ω, in order to ensure the complete
board in the second layer. The surrounding drilled hole should be blocked and the lines should be
as short as possible. !
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A πmatching circuit near the RF Pin should be reserved in RF lines. RF lines connecting the chip and
antenna should not cover drills, which means cross layer lines are not allowed.
The width of RF lines should not be less than 6 mil and should keep up to10 mil.
RF lines should not be set at a vertical, or a 45-degree angle. Circular lines are allowed if necessary.
No signal lines of high frequency should be set near RF lines.
RF antenna should be set away from high frequency transmitting devices, such as crystal oscillators,
DDR, and certain high frequency clocks (SDIO_CLK, etc).
Figure 12 ESP8266EX RF PCB Layout
2.3.2. ESP8266EX as Slave Device
When ESP8266EX is matched with CPU as a slave unit, information integrity in layout design is more
important than that in analogue design.
Due to the system accountability, the increasing high frequency signals would result in interference
in ESP8266EX. Attentions should be paid to those interferences.
Main boards in PAD or TV BOX will be discussed.!
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