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Espressif Systems ESP8285 Hardware Design Manuallines

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ESP8266
Hardware Design Guidelines
Version 2.8
www.espressif.com

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Summary of Contents for Espressif Systems ESP8285

  • Page 1 ESP8266 Hardware Design Guidelines Version 2.8 www.espressif.com...

  • Page 2: Release Notes

    About This Guide This document provides product information of ESP8266EX series, including ESP8266EX chip, ESP-LAUNCHER development board and ESP8266EX modules. Release Notes Date Version Release Notes 2015.12 V1.3 Initial release. 2016.01 V1.4 Update Section 1.5.2, Section 1.5.3 and Section 1.6. 2016.06 V1.5 Update Section 3.1.
  • Page 3 Documentation Change Notification Espressif provides email notifications to keep customers updated on changes to technical documentation. Please subscribe at https://www.espressif.com/en/subscribe. Certification Download certificates for Espressif products from https://www.espressif.com/en/ certificates.

  • Page 4: Table Of Contents

    Table of Contents 1. ESP8266EX ..........................1 1.1. Overview ............................1 1.2. Specifications ..........................2 1.3. Pin Definitions ..........................3 1.4. Schematic Checklist ........................5 1.4.1. Power Supply .......................6 1.4.2. Power-on Sequence and Power Reset .................8 1.4.3. Flash ..........................8 1.4.4. Crystal Oscillator ......................9 1.4.5. RF ..........................10 1.4.6.
  • Page 5 Module ..........................29 3.1. ESP-WROOM-S2 ........................29 3.2. ESP-WROOM-02 ........................29 3.3. ESP-WROOM-02D/ESP-WROOM-02U ...................30...

  • Page 6: Esp8266Ex

    1. ESP8266EX ESP8266EX 1.1. Overview Espressif’s ESP8266EX delivers a highly integrated Wi-Fi SoC solution to meet the continuous demand for efficient power usage, compact design and reliable performance in the industry. With its complete and self-contained Wi-Fi networking capabilities, ESP8266EX can perform either as a standalone application, or as a slave to a host MCU.

  • Page 7: Specifications

    1. ESP8266EX Interface Analog receive receive UART Registers GPIO Analog transmit transmit SDIO Sequencers Accelerator Crystal Bias circuits SRAM Flash Figure 1-1. ESP8266EX Block Diagram 1.2. Specifications Table 1-1. ESP8266EX Specifications Categories Items Parameters Standard FCC/CE/TELEC/SRRC Protocols 802.11 b/g/n/e/i Frequency Range 2.4 G ~ 2.5 G (2400 M ~ 2483.5 M) 802.11 b: ＋...

  • Page 8: Pin Definitions

    1. ESP8266EX Categories Items Parameters Package size QFN32-pin (5 mm x 5 mm) External interface Wi-Fi mode Station/SoftAP/SoftAP+Station Security WPA/WPA2 Encryption WEP/TKIP/AES Firmware upgrade UART Download/OTA (via network) Software SDK for customized development/cloud server Software development development Network Protocols IPv4, TCP/UDP/HTTP/FTP User configuration AT Instruction Set, Cloud Server, Android/ iOS app 1.3.
  • Page 9 1. ESP8266EX Table 1-2. ESP8266EX Pin Definitions Name Type Function VDDA Analog Power 2.5 V ~ 3.6 V RF antenna interface Chip output impedance = 39 + j6 Ω. It is suggested that users retain the π-type matching network which matches the antenna. VDD3P3 Amplifier Power 2.5 V ~ 3.6 V VDD3P3...

  • Page 10: Schematic Checklist

    1. ESP8266EX Name Type Function GPIO5 GPIO 5 U0RXD UART Rx during flash programming; GPIO 3 U0TXD UART Tx during flash progamming; GPIO 1; SPI_CS1 Connects to crystal oscillator output, can be used to provide BT XTAL_OUT clock input XTAL_IN Connects to crystal oscillator input VDDD Analog Power 2.5 V ~ 3.6 V...

  • Page 11: Power Supply

    1. ESP8266EX The values of C1 and C2 vary with the selection of the crystal. The value of R4 varies with the actual PCB board. The initial value will be a 0 ohm RESISTOR. VDD33 1uF(NC) 26MHz±10ppm VDD33 4.3nH 12K±1% EXT_RSTB U0TXD U0RXD...
  • Page 12 1. ESP8266EX Figure 1-4. ESP8266EX Digital Power Supply Pins 1.4.1.2. Analog Power Supply ESP8266EX has five analog pins for power supply, including Pin1, Pin3, Pin4 that are the power supply for internal PA and LNA; and Pin29, Pin30 for the internal PLL. The operating voltage for analog power supply pins is 2.5 V ~ 3.6 V.

  • Page 13: Power-On Sequence And Power Reset

    1. ESP8266EX 1.4.2. Power-on Sequence and Power Reset 1.4.2.1. Power-on Sequence ESP8266EX uses a 3.3 V system power supply. The chip should be activated after the power rails have stabilized. This is achieved by delaying the activation of CH_EN (Pin7) by time T after the 3.3 V rails have been brought up.

  • Page 14: Crystal Oscillator

    1. ESP8266EX Figure 1-6. ESP8266EX Flash 1.4.4. Crystal Oscillator ESP8266EX can support 40 MHz, 26 MHz and 24 MHz crystal oscillators.Please select the right type of crystal oscillator that is used in the ESP Flash Download Tool. In circuit design, capacitors C1 and C2, which are connected to the ground are added to the input and output terminals of the crystal oscillator respectively.

  • Page 15: External Resistor 12K

    PCB board. The initial value will be a 0 ohm RESISTOR. VDD33 1. ESP8266EX 1uF(NC) 26MHz±10ppm VDD33 4.3nH 12K±1% 1.4.5. RF 10uF 0.1uF TBD(NC) The impedance of the ESP8266 PA output end is 39 + j6 Ω, so the matched impedance is 39-j6 Ω...
  • Page 16 1. ESP8266EX (GPIO15), U0CTS (GPIO13). After the exchange, GPIO15 and GPIO13 will be connected respectively to MCU_RXD and MCU_TXD as swapped U0TXD and U0RXD for serial communication. For reference design, please refer to Figure 1-10b. Figure 1-10b. ESP8266EX UART SWAP GPIO15, the strapping pin of ESP8266EX, needs to be at low-voltage level when the chip is powered on.
  • Page 17 1. ESP8266EX Figure 1-10c. UART Voltage-level Switch circuit ⚠ Notice: When using GPIO13 and GPIO15 as serial communications, please pay attention to the direction of sending and receiving information, and they need to be connected correctively to MCU UART pins. When using the AT firmware, please note that the UART GPIO is already configured (refer to Hardware Connection).

  • Page 18: Slave Sdio/Spi

    1. ESP8266EX 1.5. Slave SDIO/SPI Figure 1-11. Schematics of ESP8266EX as a Slave SDIO Espressif Submit Documentation Feedback 2024.10...

  • Page 19: Pcb Layout Design

    1. ESP8266EX �� Note: • Please refer to the design of ESP-WROOM-S2 for further details. UART Download Mode: Jumper J1 short circuit. • SDIO Boot Mode: Jumper J1 open circuit. • If the external host CPU's SDIO or SPI interface has been pulled up, the optional pull-up resistor can •...

  • Page 20: Positioning A Esp8266Ex Module On A Base Board

    1. ESP8266EX The third layer is the POWER layer where only power lines can be placed. It is • acceptable to place some signal lines under unavoidable circumstances. The forth layer is the BOTTOM layer. Only signal lines can be laid. Placing •...

  • Page 21: Standalone Esp8266Ex Module

    1. ESP8266EX �� Note: As is shown in Figure 1-13, the recommended position of ESP8266EX module on the base board should be: Position 3, 4: Highly recommended; • Position 1, 2, 5: Not recommended. • If the positions recommended are not suitable, please make sure that the module is not covered by any metal shell.
  • Page 22 1. ESP8266EX The center ground pad at the bottom of the chip should be connected to ground plane through at least 9 ground vias. Figure 1-15. ESP8266EX PCB Layout 1.6.3.2. Crystal Oscillator Design The crystal oscillator should be placed as close to the XTAL pins as possible (without the traces being too long).
  • Page 23 1. ESP8266EX Figure 1-16. ESP8266EX Crystal Oscillators 1.6.3.3. RF Design The characteristic RF impedance is 50 Ω. The ground plane should be complete. The RF trace should be as short as possible with dense ground via stitching around it for isolation. The width of RF lines should be as short as possible and there should be dense vias stitched around.

  • Page 24: Esp8266Ex As A Slave Device

    1. ESP8266EX Figure 1-17. ESP8266EX RF Design 1.6.4. ESP8266EX as a Slave Device When ESP8266EX works as a slave device in a system, users need to pay more attention to signal integrity in the PCB design. It is important to keep ESP38266EX away from the interferences caused by the complexity of the system and an increased number of high- frequency signals.

  • Page 25: Typical Layout Problems And Solutions

    1. ESP8266EX distance between the chip and the noise sources decreases the interference and reduces the coupled noise. It is suggested that a 100 Ω ~ 200 Ω series resistor is added to the six signal traces • when ESP8266EX communicates with the CPU via SDIO to decrease the drive current and any interferences, and also to eliminate the sequencing problem caused by the inconsistent length of the SDIO traces.

  • Page 26: Typical Application

    1. ESP8266EX This problem is caused by improper layout and can be solved by re-layout. See Section 1.5 for details. 3. Q: When ESP8266EX sends data packages, the power value is much higher or lower than the target power value, and the EVM is relatively poor. Analysis: The disparity between the tested value and the target value may be due to signal reflection caused by the impedance mismatch on the transmission line connecting the RF pin and the...

  • Page 27: Smart Light

    1. ESP8266EX I2C works in the master mode and can connect to multiple sensors. The slave devices are identified through the addressing mode, as each slave device has a unique address. The sensor products send real-time data to ESP8266EX via the I2C interface, and ESP8266EX uploads the data to the server wirelessly.

  • Page 28: Esp-Launcher

    2. ESP-LAUNCHER ESP-LAUNCHER 2.1. Overview Espressif provides ESP8266EX development board—ESP-LAUNCHER for quick configuration and further development. The size of the board is 46 mm x 78.5 mm (see Figure 2-1). UART IO 13 Reset key Pin 12 USB UART Micro USB Pin 9 IO 14 Pin 10...
  • Page 29 2. ESP-LAUNCHER Table 2-1. ESP-LAUNCHER Module Description Module Functional description Micro USB There are two USB interfaces. Both can be used as a 5 V power supply or for serial interface communication (2-1-4). The USB interface provides 5 V power supply which can be converted to 3.3 V through a Power supply DC-to-DC converter.
  • Page 30 2. ESP-LAUNCHER Module Functional description There are multiple modules that can be connected to the ESP-LAUNCHER for testing and development, through the 1.27mm double-row pin headers (2-1-23) and 2.00 mm double- row pin headers (2-1-24). Test modules Please note that module pins should be connected to their corresponding pins on the board.

  • Page 31: Schematics

    2. ESP-LAUNCHER 4. Remove R58 on the PCB and disconnect GPIO14 with the infrared transmitting tube; 5. Remove the pull-down resistor R29 of MTDO/IO15 (next to J11); 6. When downloading firmware, pull the IO15/CS at J11 to low level and toggle the switch of GPIO0 inwards to enable UART Download mode;...

  • Page 32: Power Supply

    2. ESP-LAUNCHER 2.3.2. 5V Power Supply Figure 2-3. ESP-LAUNCHER 5V Power Supply Schematics 2.3.3. Test Module Figure 2-4. ESP-LAUNCHER Test Module Schematics Espressif Submit Documentation Feedback 2024.10...

  • Page 33: Test Board

    2. ESP-LAUNCHER 2.4. Test Board A test board is embedded in ESP-LAUNCHER, as shown in Figure 2-5. The external size of the test board is 20 mm x 31 mm. A 2-dBi SMA antenna or other testing equipment can be connected to the test board via the SMA antenna connector.

  • Page 34: Esp8266Ex Module

    3. ESP8266EX Module ESP8266EX Module Espressif provides two types of modules, the SMD module (ESP-WROOM-02) and the DIP module (ESP-WROOM-01). The modules have been improved to achieve the optimum RF functionality. It is recommended that users use these modules for testing or further development.
  • Page 35 3. ESP8266EX Module Figure 3-2. ESP-WROOM-02 Module For details of ESP-WROOM-S2, please refer to ESP-WROOM-02 Datasheet. 3.3. ESP-WROOM-02D/ESP-WROOM-02U The module size of ESP-WROOM-02D is (18 ± 0.2) mm x (20 ± 0.2) mm x (3 ± 0.15) mm. The type of flash used on this module is an SPI flash with a package size of SOP 8-150 mil. The gain of the on-board PCB antenna is 3 dBi.
  • Page 36 3. ESP8266EX Module Figure 3-4. ESP-WROOM-02U Module For detailed information on ESP-WROOM-02D/ESP-WOOM-02U, please refer to ESP- WROOM-02D/ESP-WROOM-02U Datasheet. Espressif Submit Documentation Feedback 2024.10...
  • Page 37 The Wi-Fi Alliance Member logo is a trademark of the Wi-Fi Alliance. The Bluetooth logo is a registered trademark of Bluetooth SIG. All trade names, trademarks and registered trademarks mentioned in this document are property of their respective owners, and are hereby acknowledged. Copyright © 2024 Espressif Systems (Shanghai) Co., Ltd. All rights reserved. www.espressif.com...

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