SparkFun USB to Serial UART Boards Hookup Guide

Contributors: .Brent.
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SparkFun has a line of USB to serial UART bridge products designed to allow a user to communicate with a serial UART through a common USB port. It is harder to find computers with serial UART ports on them these days, but super common to find serial devices. Many of the official Arduino and clones share a common interface. This interface is essentially the 6 pin Single-In-Line (SIL), 0.1” pitch version of FTDI's TTL-232R cables.

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The key change from the FTDI cables to our Arduino compatible boards is that we swapped pin 6 from RTS to DTR. This change was required to match Arduino's method of resetting the ATmega328P using the DTR signal.

FTDI Pinout

Arduino compatible pinout is slightly different from the FTDI cable (pin 6)

Note The signal difference on pin 6 may cause these devices to not be 100% compatible with devices designed for use with the FTDI TTL-232R cables.


Having a detachable USB to UART bridge comes with several advantages over boards like the Arduino Uno.

  • Removing the computer interface makes the board smaller.
  • You only need to buy the circuit once and can program many Arduinos.
  • The bridge circuitry draws power (up to 500 mW) that's not needed in many installed applications. Removing this parasitic drain makes your project more power efficient & your batteries last longer.

Suggested Reading

Before we get started, you might want to review this other tutorial: