Isolated USB UART

Name: Isolated USB UART
SKU: 250
Price: 18.00 USD
Availability: Discontinued
Rating: 4.42 (3 reviews)

(3 Reviews) Designed by partially stapled in United States of America

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A super useful, super safe way to talk logic-level serial to your projects over USB. This is a great replacement for your FTDI serial cable! A handy on-board pull-down transistor can reset your micro…

Features

1Mbit data rate serial port with transmit and receive
USB 2.0 compliant, with Micro-B type connector
1000Vrms isolation -- no more ground loops through your PC
Your project supplies 2.5-5.5 volts to set the input/output line voltage -- no level shifter required
Extra output with pull-down transistor to reset your project for programming
Power, transmit, and receive LEDs
Windows, Linux and Mac compatible -- Uses the popular FTDI series of UART chips
Configurable -- disable LEDs, make them toggle or blink, invert UART polarity, and customize VID/PID and device strings
Open Source -- design documents available under the Creative Commons Attribution 3.0 license including gerbers and schematic PDF

What you get

You get what you see -- one PCB, fully assembled. No cable is included but any USB Micro-B cable will work. Everything is pre-programmed to work right away. Just connect it, fire up your terminal app, and start hacking!

What it's made of

The Isolated USB UART is open-source hardware, provided under the Creative Commons Attribution 3.0 license. It was developed using Altium Designer but a PDF of the schematic as well as the Gerber and NC Drill outputs is provided below. The current revision number is 4.

All parts and materials are RoHS-compatible and only lead-free solder is used.

Documentation
UART - FT230X
Isolator - SI8431AB
Schematic PDF (revision 4)
Source bundle - recommended (revision 4)
Mercurial source control repository

Resources

Virtual COM port driver - for Windows
FT_Prog - utility for re-programming

Review Breakdown

Average Ratings

Product: (4.67)

Documentation: (4.33)

Shipping: (4.33)

Communication: (4.33)

Arie | Nov. 14, 2014

Essential device for debugging unisolated UART interfaces

Device works well, very handy when connecting to MCUs and crossing voltage domains.
Very handy for car related stuff and non-isolated mains powered stuff.
Worth the money, very handy device !

Darren | Oct. 21, 2014

Works great.

Very handy for debugging any of a variety of devices that happen to have UARTs. Totally plug and play on OS X. We never even looked at the doc. Just plug it in, hook up VCC, GND, TX and RX and off it goes. Remember TX is from your computer, not your device, so plug your device's RX into the pin labeled TX and vice versa. We guessed right the first time on this.

We just ordered three more of these. We need extras in the lab so we aren't always fighting over the one we have.

Maarten | Sept. 2, 2014

Works well, but took more effort to set up than I expected

The cable works great, but when powered on it will pull the reset pin low by default. I have to send some obscure command using either an FTDI-specific library or low-level USB functions. A bit more info about this would have been helpful. In case anyone else is trying to figure this out, this is the command you need (from libftdi):

Pull reset low: ftdi_set_bitmode(ftdi, 0xf1, BITMODE_CBUS)
Release reset: ftdi_set_bitmode(ftdi, 0xf0, BITMODE_CBUS)

After doing this, the device works as expected. However, if you use libftdi to transmit/receive data, you should set the baud rate to four times the actual baud rate because there's something wrong with the internal baud rate calculation.

I'm actually running the device at 2Mbaud, which is twice as high as the maximum specified speed, but it works fine for me.

One small suggestion: If you used clear heat shrink instead of black, you would be able to cover the entire board with it without blocking any labels or LEDs.

UPDATE: Your board has some EMI issues. Whenever I turn the mains switch on my power supply on or off, it seems to create an EMI spike powerful enough to reset the FTDI chip on your board. The power LED turns off for a moment and the USB device disconnects and then reconnects to the computer. I suspect the cause of the problem is that you don't have enough capacitors on the 5V line. You only have 100nF after the ferrite bead, the FTDI datasheet recommends 10nF before the ferrite bead and 100nF+4.7uF after it. This is disappointing because I was planning to use this device in a noisy environment (that's why I needed isolation in the first place).