The FTDI USB to TTL serial converter module

The FTDI USB/UART module (FTDI programmer)

The FTDI USB to TTL serial converter module is an UART (universal asynchronous receiver-transmitter) board used for TTL serial communication. It is a breakout board for the FTDI FT232R chip with an USB interface, can use 3.3 or 5 V DC and has Tx/Rx and other breakout points.

This is an ongoing post. Please suggest corrections, explanations, etc. in the comment section at the bottom of this page.

FTDI USB to TTL serial converter modules are used for general serial applications. It is popularly used for communication to and from microcontroller development boards such as ESP-01s and Arduino micros, which do not have USB interfaces.

FTDI USB to TTL serial converter module

Original FT232R chips are one of the newer chips manufactured by FTDI (Future Technology Devices International). Apart from being an USB to serial UART, it has an integrated EEPROM and optional clock generator output. The chip also incorporates FTDIChip-ID functionality (giving each chip an unique identifier for security) and USB termination resistors. Cloned boards (with a cloned chip) will likely exclude the unique ID functionality and does not include an EEPROM, meaning that signals cannot be inverted.

The internal clock (6MHz, 12MHz, 24MHz and 48MHz) can be brought out of the device and used to drive a microcontroller or external logic.

The module has a mini-B USB port which is used to connect to an USB port of an interfaced device (e.g. a PC). On the other side, the FTDI USB to TTL serial converter module has breakout pins (Tx, Rx, Vc and GND) that is connected to a microcontroller’s corresponding pins. Communication takes place using TTL (transistor-transistor logic). It has a 3.3/5V DC jumper and will supply 500 mA through its Vc pin.

FTDI USB to TTL serial converter module specifications

Chip: FT232R (FTDI)
Pins: 6 pin headers and 18 through hole connectors. DTR, RX, TX, VCC, CTS, GND and PWR, TEN, SLEEP, CTS, 3.3V, 5V, RXL, TXL, GND x 2, TXD, DTR, RTS, VCC, RXD, R1, RSD, DCD (all marked)
Working voltage: 5V DC
Level output: 3.3 – 5 V DC (jumper)
Interfaces: Serial/UART
On-board LEDs: power on, Rx, Tx transmission, working status
Operating current: 500mA
Module size: 36 x 18 mm
Pin size: male, 5 x 2.54 mm
Ports: Micro-B USB
Breadboard friendly: yes

FTDI USB to TTL serial converter module pinout

FTDI USB to TTL serial converter module pinout
The FTDI USB to TTL serial converter module pinout. Also note the 3.3 V / 5V jumper connector for the VCC pin.

The FTDI USB to TTL serial converter module has six, male, 5 x 2.54 mm header pins and 18 through hole connectors. The header pins are breadboard friendly and all the pins/connectors are clearly marked.

The more commonly used pins (RX, TX, VCC and GND) are connected to the corresponding pins of the microcontroller (RX -> TX and TX -> RX).

The DTR pin is connected to the reset pin of the microcontroller, which will trigger an auto-reset signal after a sketch is uploaded.


Some devices might need drivers to register the the FTDI USB to TTL serial converter module to be able to appear as a COM port. This allows application software to access the module in the same way as it would access a standard COM port. Although some operating systems might install the drivers automatically after its first use, others might need these drivers to be installed manually. For more information, visit the official FTDI Virtual COM Port Drivers page.

To get started you will need

These were the parts that were used. Most are available from BangGood, eBay and RS Components. Direct links to some of the parts are supplied lower down.

  • FTDI USB to TTL serial converter module
  • Mini-B USB cable
  • Breadboard and solderless breadboard jumper cable set
  • 8x 10, 20 or 30cm female-to-female breadboard jumper wire cables (optional)

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