One click download scheme of serial port of esp32 / esp8266 series single chip microcomputer without peripheral circuit

One 、 summary

CH340X、CH343、CH342 etc. USB The serial port chip supports no peripheral circuit ESP32/ESP8266 Single chip microcomputer serial port one click download function , For this kind of MCU that supports multi-mode startup , No logic control circuit such as peripheral triode is required , Connect the output signal pin provided by the chip directly MCU Of BOOT Control pin （GPIO0） And CHIP_PU Chip enable pin （EN） That is to say MCU BOOT and APP Mode control switching and firmware download .

Two 、 Program features

• The circuit is simple and reliable , Power on the serial port 、 Power down 、 open 、 Closing and other operations do not affect MCU Operation mode . The traditional one click download circuit needs 2 Three triodes are used together to keep BOOT Normal low level and prevent serial port software switching MCU False reset or false entry BOOT Download mode .
• ESP The original download software of Series MCU can be used directly , No need to change .
• Support automatic download . utilize USB Hot plug features and CH343PT library , It can be realized on the software side USB Automatically download after the device is inserted .
• Provide QFN16、ESSOP10、SOP16 Equal package , Can also be customized .
• CH340X Support 5V Withstand voltage and prevent inward current backflow .
• CH343 Support serial port IO Independent power supply , Can support 5V/3.3V/2.5V/1.8V Equal serial communication , Support anti inward current backflow . The minimum power consumption in standby mode is only 2uA.

3、 ... and 、 Download the principle and circuit description

ESP series MCU Boot mode ：

MCU Reset for low level , Hardware needs to meet MCU Enter automatically after reset “ Serial download ” Pattern . Download timing diagram ：

 CH340X/CH343P and MCU Serial connection reference ：

be based on CH340X Realized ESP32/8266 series MCU One click download circuit

  be based on CH343P Realized ESP32/8266 series MCU One click download circuit

  When downloading with one click , Download software from the computer and open the serial port , First set up DTR#（IO0） Low level 、 Set up RTS#（EN） Low level 、 Higher level ,MCU Automatic reset enters BOOT Download program . When the download is complete , Need to restore DTR High level 、 Set up RTS#（RESET） Low level 、 Higher level ,MCU Run the application normally after automatic reset .

notes ：

1. CH340X chip ,5# Feet and 6# Series connection between pins 3～5.6KΩ Resistance time #6 The foot will automatically switch to push-pull output DTR# function , The pin defaults to strong high level , Set by the application DTR Pin out high and low level .
2. CH340X The serial port voltage is determined by the chip VCC The supply voltage determines ,CH343 The serial port voltage is determined by the chip VIO The supply voltage determines , Pay attention to voltage matching when using .
3. Need to cooperate CH341SER V3.7 And above driver .

（ Download link ：CH341SER.EXE - Nanjing qinheng Microelectronics Co., Ltd )

Four 、 Download software and demo effect

ESP32 Series single-chip microcomputer flash_download_tool Software download Demo