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USB to Serial / UART 5V or 3.3V

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USB to Serial / UART 5V or 3.3V

USB to Serial Adapter is a USB to Serial bridge so you can upload programs to an ESP8255 or communicate with your microcontroller's serial port through your PC's USB interface. The pinout is standard [ GND - CTS - Vd - TX - RX - RTS ] and will work with any Arduino clone that has this as a programming interface. The signals can be switched between 5V levels and 3.3V levels and the voltage on the Vo pin changes as well. When operating at 3.3V this USB to Serial Adapter can supply a beefy 250mA at the Vo pin for power hungry devices such as the ESP8255. When operating at 5V it can supply up to 500mA before the PolyFuse will switch to a high impedance state to protect against short circuits. When operating at 3.3V the voltage regulator has a 400mA current limit..


 Each pin is clearly labeled and the pads are nice and big for easy soldering of the pins.  


3.3V USB to Serial adapter I discovered most can deliver only 50mA at 3.3V. This is not enough to power some of the newer 3.3V micros and the very popular ESP8266. This design can power the ESP8266 directly and has been tested with it.


The when the toggle of the slide switch is closest to the USB connector then the signals and Vo are at 5V levels (same as the USB power) and when the toggle is closest to the output pins then the signals are 3.3V levels and Vo is supplied from the on board LDO.


There are two LEDs indicating activity, the Red one flashes when the Rx signal is active and the green one flashes when there is activity on the Tx line.


The USB to Serial IC used on the board is the CH340G designed by WCH Co Ltd. I prefer this IC over the FTDI chips because it does not increment the serial port number every time a new device is connected to the same USB port. Each USB port gets assigned a COM port number when the USB2Serial is first plugged into it. The next time I plug a board into that port it uses the same serial port number. If I plug it into a different port, it gets a different COM port number. This is really important if you use many different serial adapters or test them. Trust me, Windows 7 crashes very badly when the COM port number exceeds 256.


The USB2Serial also supports non-standard Baud rate such as 56000, 57600 and 76800 used by some boot loaders when uploading software (such as the ESP8266 bootloader).


 The board is assembled on our pick and place machine and is reflow soldered.



  • Switchable between 5V and 3.3V levels

  • 3.3V output can supply 250mA continuously, 300mA for short periods

  • Has a constant COM-port assigned

  • RX/TX LEDs

  • Based on CH340G

  • Mini USB-connector for ruggedness

  • Baud rates: 50,75,100,110,134.5,150,300,600,900,1200,1800,2400,3600,4800,9600,14400,19200,28800, 33600,38400, 56000,57600,76800,115200,128000,153600,230400,460800,921600,1500000,2000000

  • Made in the USA

  • Half the Price of Similar Modules


0.7" x 1.4"

18mm x 35mm


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