USB to Serial UART Boards Hookup Guide Datasheet by SparkFun Electronics

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SparkFun USB to serial UART Boards Hookup
Guide
Introduction
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.
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.
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.
Advantages
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.
any a u u (Mike-e a: . ,. . . spEarkfun a; an
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:
Installing FTDI Drivers
Hardware Tour
The interface to this line of boards is simple. One side has a TTL-232R
cable compatible 6 pin SIL, 0.1” pitch female header. This side connects to
the Arduino (TTL serial UART) board. We often use right angle headers on
the Arduino Pro Mini to make connecting a serial bridge trivial. Our boards
have silkscreen labels of where the black and green wires of the FTDI TTL-
232R cables would be.
Fritzing diagram showing the connection between a USB to UART bridge
and a Pro Mini
6 pin SIL, 0.1” pitch header at top of PCBA
The other side has a USB mini-B or USB micro-B jack. A standard USB
cable is used to connect this jack to a host computer.
This line of products comes in a few forms. Here is a table comparing the
most common options.
Name Voltage Current Limit Connector
SparkFun FTDI Basic
Breakout - 5V
5.0 V N/A USB Mini-B
SparkFun FTDI Basic
Breakout - 3.3V
3.3 V < 50 mA USB Mini-B
Beefy 3 3.3 V < 600 mA USB
Micro-B
1
2
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Name Voltage Current Limit Connector
LilyPad FTDI Basic Breakout -
5V
5.0 V N/A USB Mini-B
Table 1. Comparison of common SparkFun offerings
Warning: These boards are for prototyping ONLY. Unlike commercial
devices, power negotiation and suspend mode do not occur, and it is
possible to overload the USB host. Exercise caution when connecting
a load, and never connect a load that draws too much current.
Connecting the USB to Serial UART
Boards
These bridges have two connections. On one end there is a USB device
connection. See table 1 for more details on the exact connector for the
specific product. This interface is USB 1.1 / USB 2.0 full-speed compatible.
A standard USB A to some sort of B cable is used to connect the bridge to
the computer.
The other connection is a 0.1" pitch female header designed to connect to
the microcontroller. Many of our products come with a compatible row of
plated-through holes. These are designed to have 0.1" male headers
soldered in. Some cases will best be served with straight headers, other
with right-angle headers. The desired connection varies from design to
design as discussed here. Some products come prepopulated with these
headers.
Prepopulated FTDI header example
1
1. [5V is taken directly from V and is only limited by the USB host controller.]
BUS
2. [This 3.3V regulator is powered directly from V and is only limited by the USB host controller.]
BUS
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