Products Manual
USB-TTL - USB to TTL Level Serial Converter Board


  • Adds a high speed TTL level serial interface via USB connection.

  • Provides 3.3V or 5V TTL level serial interface for most microcontroller interfaces.

  • Provides +5 VDC or +3.3 VDC power for external devices such as microcontroller, Wi-Fi, Bluetooth, Xbee, etc.

  • 384 bytes receive data buffer.

  • 128 bytes transmit data buffer for high speed throughput.

  • Signals: RxD, TxD, RTS#, CTS#.

  • Requires no IRQ, DMA, I/O port.

  • Data rates: 300 bps to 1M bps.

  • Provides terminal block connector for easy connection.

  • Monitor LEDs of TxD, RxD indicating port status.

  • Dimensions : 60 mm X 30 mm, with USB A type connector.
                         45 mm X 30 mm, without USB A type connector.

  • Virtual COM port drivers for Windows 8, 7, Vista, XP, 2000.

  • Powered by USB port. No external power adapter required.

  • CE, FCC approval.

  • Supports Windows 8, Windows 7, Vista, 2003, XP, 2000 and Linux

  • Supports Mac OS X 10.9 and above, This driver is signed by Apple


Compliance USB 1.0/1.1 compliant, USB 2.0 compatible
Speed 12 Mbps, full-speed USB
FIFO 128 byte transmit FIFO
384 receive FIFO
Serial Interface
Port Type TTL level
Number of Ports 1
Connectors Terminal Block
Serial Port Speed
Baudrate 300 bps to 921.6k bps
Serial Communication Parameters
Data Bits 5, 6, 7, 8
Stop Bits 1, 1.5, 2
Parity None, Even, Odd, Space, Mark
Flow Control RTS/CTS, XON/XOFF
Serial Signals
TTL level TxD, RxD, RTS, CTS
Driver Support
OS Windows 7, Vista, 2003, XP (WHQL certified) and 2000
Linux Kernel 2.4 and up built-in support
Power Supply
Input Powered by USB port
No external power adapter required

Diagram of USB-TTL

Setting USB-TTL for 5V or 3.3V Operation

USB-TTL has two 1x3 header blocks, which have jumpers to enable the output power (JP2) and TTL level of serial interface for 5V or 3.3V operation (JP1). Please refer to below the illustration of the jumper setting for 5V and 3.3V operation.

  Jumper Function  
Sets serial interface to 5V TTL level.  
Sets serial interface to 3.3V TTL level.  
Provides a +5VDC output power for TB1 VCC pin (pin1).  
Provides a +3.3VDC output power for TB1 VCC pin (pin1).  

Terminal Block (TB1) Pinout Information

  Pin Number Pin Type Description  
  VCC (pin1) Power +5VDC or +3.3VDC output power (select by JP2)  
  RXD (pin2) Input RXD: Receive Data (TTL level)  
  TXD (pin3) Output TXD: Transmit Data(TTL level)  
  RTS# (pin4) Output RTS# : Request To Send,Active low (TTL level)  
  CTS# (pin5) Input CTS# : Clear To Send,Active low (TTL level)  
  GND (pin6) Ground GND: Signal Ground  

LED Indication

  LED color Name Description  
  Green TXDLED Indicating the data output to external serial device  
  Yellow RXDLED Indicating the data input from external serial device  
  Red PWRLED Power on and output power is ready