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Espressif Systems ESP8266 Series Hardware Design Manuallines

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ESP8266
Hardware Design Guidelines
www.espressif.com
Version 2.4
Espressif Systems
Copyright © 2018

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Summary of Contents for Espressif Systems ESP8266 Series

  • Page 1 ESP8266 Hardware Design Guidelines Version 2.4 Espressif Systems Copyright © 2018 www.espressif.com...
  • Page 2 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: Table Of Contents

    Table of Contents 1. ESP8266EX ..........................1.1. Overview ............................ 1.2. Specifications ..........................1.3. Pin Definitions ..........................1.4. Schematic Checklist ........................1.4.1. Power Supply ....................... 1.4.2. Power-on Sequence and Power Reset ................. 1.4.3. Flash ..........................1.4.4. Crystal Oscillator ......................1.4.5. RF ..........................
  • Page 4 2.4. Test Board ..........................3. ESP8266EX Module ......................3.1. ESP-WROOM-S2 ........................3.2. ESP-WROOM-02 ........................3.3. ESP-WROOM-02D/ESP-WROOM-02U ...................

  • Page 5: 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 6: 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 2.4G ~ 2.5G (2400M ~ 2483.5M) 802.11 b: ＋20 dBm...

  • Page 7: 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...
  • Page 8 1. ESP8266EX " Table 1-2. ESP8266EX Pin Definitions Name Type Function VDDA Analog Power 2.5V ~ 3.6V 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 2.5V ~ 3.6V VDD3P3 Amplifier Power 2.5V ~ 3.6V VDD_RTC...

  • Page 9: 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...

  • Page 10: Power Supply

    1. ESP8266EX " 6.8pF 6.8pF VDD33 1uF(NC) 26MHz±10ppm 12K±1% VDD33 4.3nH UTXDA 499R UTXD URXD 10uF 0.1uF TBD(NC) VDD33 ANT1 GPIO5 VDDA GPIO5 2.2nH WIFI_ANT SDI/SD1 SCS/CMD SDI/SD1 SD_DATA_1 SDO/SD0 VDD3P3 SD_DATA_0 200R SCK/CLK SCK/CLK SDO/SD0 VDD3P3 SD_CLK SCS/CMD VDD_RTC SD_CMD SWP/SD3 SHD/SD2...
  • Page 11 1. ESP8266EX " CHIP_EN SD_DATA_2 XPD_DCDC VDDPST ESP8266EX VDD33 " 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 2.5V ~ 3.6V.

  • Page 12: 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 3.3V 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 3.3V rails have been brought up.

  • Page 13: Crystal Oscillator

    1. ESP8266EX " VDD33 GPIO5 GPIO5 SDI/SD1 SCS/CMD SDI/SD1 SD_DATA_1 SDO/SD0 SD_DATA_0 200R SCK/CLK SCK/CLK SDO/SD0 SD_CLK SCS/CMD SD_CMD SWP/SD3 SHD/SD2 SWP/SD3 SD_DATA_3 /HOLD SHD/SD2 SD_DATA_2 VDDPST FLASH " Figure 1-6. ESP8266EX Flash 1.4.4. Crystal Oscillator ESP8266EX can support 40 MHz, 26 MHz and 24 MHz crystal oscillators. The accuracy of crystal oscillators should be ±...

  • Page 14: External Resistor 12K

    1. ESP8266EX " 1.4.5. RF The impedance of the ESP8266 PA output end is (39+j6)Ω, so the matched impedance is (39-j6)Ω (from antenna to the chip). ANT1 VDDA 2.2nH WIFI_ANT VDD3P3 VDD3P3 VDD_RTC TOUT 2.4pF 3.0pF CHIP_EN XPD_DCDC " Figure 1-8. ESP8266EX RF 1.4.6.

  • Page 15: Slave Sdio/Spi

    1. ESP8266EX " 1.5. Slave SDIO/SPI MTMS MTMS EXT_RSTB MTDI MTDI RES12K VDDPST VDDA MTCK MTCK VDDD MTDO MTDO XTAL_IN GPIO2 GPIO2 XTAL_OUT GPIO0 GPIO0 U0TXD GPIO4 GPIO4 U0RXD XOUT Figure 1-11. Schematics of ESP8266EX as a Slave SDIO
 Espressif "...

  • Page 16: 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 17: Positioning A Esp32 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 18: Standalone Esp8266Ex Module

    1. ESP8266EX " �� Note: As is shown in Figure 1-13, the recommended position of ESP32 module on the base board should be: • Position 3: Highly recommended; • Position 4: 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 19 1. ESP8266EX " width of the power lines and the diameter of the drill should be 1.5 times that of the radius of the vias. The center ground pad at the bottom of the chip should be connected to ground plane through at least 9 ground vias.
  • Page 20 1. ESP8266EX " " Figure 1-16. ESP8266EX Crystal Oscillators 1.6.3.3. RF Design The characteristic RF impedance is 50Ω. 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 21: 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 22: 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 100Ω~200Ω 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 23: Pcb Layout Design

    1. ESP8266EX " This problem is caused by improper layout and can be solved by re-layout. See Section 1.5 for details. 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 24: 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 25: 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...
  • Page 26 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 5V power supply or for serial interface communication (2-1-4). The USB interface provides 5V power supply which can be converted to 3.3V through a DC-to-DC converter.
  • Page 27 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 28: 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 29: Power Supply

    2. ESP-LAUNCHER " 2.3.2. 5V Power Supply EXT_5V EXT_5V CON2 0.1uF 4.7uF VDD33 AN_SY8088 2.2uH CON3 4.7uF Toggle Switch 680K 6.8pF 22uF RED LED 150K 5V Power LED " Figure 2-3. ESP-LAUNCHER 5V Power Supply Schematics 2.3.3. Test Module VDD33 TOUT TOUT CH_EN...

  • Page 30: 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 31: 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 32: Esp-Wroom-02D/Esp-Wroom-02U

    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 33 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 " 2018.12...
  • Page 34 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.

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