SparkFun FT231X Breakout

Introducing the 3.3V SparkFun FT231X Breakout board, complete with the full UART hardware handshake feature! The pinout of this board matches the FTDI cable to work with official Arduino and cloned 3.3V Arduino boards. It can also be used for general serial applications. This board still brings out the DTR pin as opposed to the RTS pin of the FTDI cable. The DTR pin allows an Arduino target to auto-reset when a new Sketch is downloaded. This is a really nice feature to have and allows a sketch to be downloaded without having to hit the reset button. This board will auto reset any Arduino board that has the reset pin brought out to a 6-pin connector.

The coolest thing about the FT231X Breakout is that we have broken out ALL the pins for your use, making this board all the more hackable! It also uses a common microUSB jack.

One of the features of this board is a jumper on the back, which allows the VCC output to be configured to either 3.3V or 5V. This board ships default to 5V, but you can cut the default trace and add a solder jumper if you need to switch to 3.3V. It should be noted, however, that the max input of the FT231X through the pin labeled 3.3 on the breakout is only 3.3V but it can operate down to 1.8V with external pull ups. I/O is still 5V tolerant.

SparkFun FT231X Breakout Product Help and Resources

Core Skill: Soldering

This skill defines how difficult the soldering is on a particular product. It might be a couple simple solder joints, or require special reflow tools.

1 Soldering

Skill Level: Noob - Some basic soldering is required, but it is limited to a just a few pins, basic through-hole soldering, and couple (if any) polarized components. A basic soldering iron is all you should need.
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Core Skill: Electrical Prototyping

If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.

2 Electrical Prototyping

Skill Level: Rookie - You may be required to know a bit more about the component, such as orientation, or how to hook it up, in addition to power requirements. You will need to understand polarized components.
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Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • Member #701451 / about 6 years ago / 1

    Would it be possible use only the 3.3V supply only without any communication from the USB data pins?

    I tried to connect the device to a cell phone battery (5V) and the board powers up for about 10 secs. before shutting down.

  • signal7 / about 9 years ago * / 4

    It would be nice if these boards actually came with a header for a real jumper rather than solder traces/bridges. I'm lazy and when I need to switch from 3.3v to 5v, I'm not really looking forward to the extra work of solder/desolder to get what I want. ;-) It only requires about 0.4 inches of board real estate (well, you could use smaller headers too, I suppose) and I'm even willing to take the time to install the header myself.

    My other FT232 boards are voltage selectable via some wire-wrap connections, but that can be error prone if you're not double-checking your work.

    • Member #544161 / about 7 years ago / 1

      I know this is old, but I just bent the leads on a tiny switch, soldered it right on there and added a little dab of hot glue for strain relief. Not sure if it would break anything but I make sure to disconnect the USB before switching. So far I've been going back and forth for about 2 years without any problems!

      • bennard / about 7 years ago / 1

        Ive tried doing that a couple times too and my wires eventually broke off the jumper pads. I didn't like the dangling switch either.

        I think one of the lessons we are supposed to get from SFE is to take what they give us and run with it. I modified their SFE eagle file to include a DPDT SMD slide switch and a couple leds to indicate voltage (red-5v green-3v3). My FT231x board does exactly what I want it to.

  • Member #26075 / about 9 years ago / 2

    Has anybody used this board to program a Picaxe?

    • jjw / about 9 years ago / 1

      I have used the FT232R breakout to program the Picaxe. The trick there was to invert the lines using FT_Prog (

  • Member #156731 / about 9 years ago * / 2

    Nice board but seams to have a micro usb connector. Not my favorite flavour...

  • bobc / about 7 years ago * / 1

    The TX led on my board didn't work, on closer examination and referring to the Eagle board file it appeared to be in the wrong orientation compared to the RX LED, so I resoldered it but it still didn't work. I then discovered the TX LED orientation is correct but appears to be a high brightness type, and with 1K and 3V is doesn't light up. I replaced with a normal Red LED and it works.

    The photos above show different LEDs for TX and RX.

    Otherwise, great little board. I've written some code to control the CBUS lines, very handy!

  • Member #513507 / about 8 years ago / 1

    Can this be used to upload sketches to an Atemga328 with an uno bootloader running at 5V/16MHz? I am able to able to view data through the com port, but get sync errors when uploading a sketch.

    • M-Short / about 8 years ago / 1

      It sound work just fine although it sounds like the issue is with your reset circuit. Either manually reset the chip or add a 0.1uF capacitor between the DTR pin and the reset pin.

      • Member #513507 / about 8 years ago / 1

        Neither option is working unfortunately. There is a 0.1 uF cap in series with the DTR and reset pins, same layout as the pro mini, but still get the out of sync error. Haven't had any success with manual reset either. The reset pin works fine, either through momentary switch or ISP programming, and there is connectivity between the DTR and reset pins through the cap. Thoughts on diagnostic tests to pinpoint the problem would be appreciated. Thanks.

        • M-Short / about 8 years ago / 1

          Make sure your chip is running at 16MHz and the code was properly compiled for 16MHz (if you just used the official Arduino hex file it is). If you are still having problems email

  • Member #430576 / about 8 years ago / 1

    From the Arduino IDE, what programmer to you choose?

    • M-Short / about 8 years ago / 1

      It doesn't matter. The programmer selection is for using an AVR programmer over ISP, with the FTDI board you are programming using the bootloader over serial.

  • Member #595477 / about 8 years ago / 1

    Where can I download FT231X EagleCad part? it seems the latest version has 230 and 232

  • Member #464839 / about 8 years ago / 1

    Hi, I am not good @electronics. What is the use of SJ2 & SJ3 (Jumper)?

  • Member #464839 / about 8 years ago / 1

    In Schematic PDF, what is the use of SJ2 & SJ3?

    • M-Short / about 8 years ago / 1

      It looks like you can cut the traces to disconnect the LEDs.

  • schizobovine / about 8 years ago / 1

    What're the difference between FT232RL and the FT231X breakouts? Obviously mini vs. micro USB connectors are one.

    I ask because the description for the FT231X says it's a drop-in replacement for the FTDI basic cable. However, the Arduinos with USB based on the ATMega328PU (i.e., not the ATMega32U4 with built-in USB comms), like the RedBoard or Adafruit's USB Boarduino, all seem to use the FT232RL instead.

  • Member #464666 / about 8 years ago / 1

    Can I use this board for 1.8v UART?
    I want to read the serial console output from an ODROID board, which uses 1.8V. If so, can anyone explain how?

  • daramora / about 9 years ago / 1

    So can this program both 3.3V and 5V arduino pro mini?

    • jimblom / about 9 years ago / 1

      Yup. The output voltage of this board is selectable between 3.3V and 5V. The output logic levels will always be 3.3V (5V input tolerant though), which'll work for a 5V pro mini too.

      To select the VCC and DTR output voltage, there's a 2-way jumper on the backside (three bare solder pads, next to the 's'). By default it comes shipped set to 5V. To set it to 3.3V, cut the tiny jumper between the 5V and middle pads, and then make a solder blob to connect the 3.3V and middle pads.

      • Member #409860 / about 9 years ago / 1

        The product description indicates that it ships 3.3v by default. Is that correct?

        Also are dtr and vcc only broken out on the front? Looking at this for use on a breadboard and it looks like you'd have to pick the front or sides for headers.

        Thanks, Karl

        • jimblom / about 9 years ago / 1

          Shoot...that's not correct. I fixed the description, thanks for catching it.

          DTR is only broken out on the header opposite the USB connector. But it's on the corner, so it'll also work with the rest of the side headers. VCC's only on the 6-pin header too, but both 3.3V and 5V are broken out on the side headers. You should have access to everything if you want to breadboard it.

          • Member #409860 / about 9 years ago / 1

            Thanks! One more question. Based on the description, are all pins other than VCC and 5V operating at 3.3v levels? If so, if I only use the 3.3v pin for power and never go near VCC/5V is there any reason for me to cut the trace to use this as a 3.3v board?

            • jimblom / about 9 years ago / 1

              If you need DTR at 3.3V, you'll still want to cut/jump the trace. DTR's got a level-shifting circuit on it, and it'll shift the to whatever VCC is set to on the jumper. (Had to boost it because the reset pin on an Arduino is pretty restrictive on what it counts as a logic high -- 3.3V wouldn't cut it if the micro was running at 5V).

              • R3ST4RT / about 8 years ago / 1

                Hi Jimb0,

                I'm currently adding the FT231X onto one of my boards. I got in contact with an engineer at FTDI and he said that the FET that you have on the DTR line is unnecessary. Supposedly as long as you have a voltage appropriate pullup resistor of 10K or greater, DTR should be able to pull down the line effectively.

                Since the higher voltage of the pullup overrides the 3.3V of the DTR line, you shouldn't have any issues with a "logic high".

                This of course is only applicable for voltages of 5V or less.


  • CF / about 9 years ago / 1

    The Eagle Files are linked to the gerber files.

    • Member #64829 / about 8 years ago / 1

      This appears to still be the case 2 years later... the "Eagle Files" link actually points to a zip of the gerber files.

      • Ah, good catch! Not sure how that one slipped through the cracks - we'll get it updated. Thanks!

  • Phil18 / about 9 years ago / 1

    I agree with Member #156731 about not wanting to purchase Sparkfun boards with Micro USB connectors. Of the many Micro USB connected boards I've bought from Sparkfun, only one still has the Micro USB port still attached however it's partially separated and I was able to catch it in time to add a couple drops of Super Glue to reattach the base feet to the board.

    • jimblom / about 9 years ago / 1

      I certainly understand the concern about the micro connectors ripping off. It's the way the connectors are trending, though; and it keeps the board smaller.

      We are continuing to revise both our PCB footprint and the assembly/testing process for these. Check out this board's Eagle files for our most recent version of the fp. We added a couple solder pads under the connector to help strengthen the connection, and it's been working really well. Really have to try to rip the connector off now. That said, it still doesn't hurt to be gentle, or hold a thumb on the connector, when disconnecting the cable :).

      • Member #396977 / about 9 years ago * / 3

        If you would add a couple of thin slots on either side of the connector, a user could add a Zip-Tie, which could then be placed around the connector and thru to the back of the board and give it a fair bit of mechanical strength. You would have to move the vias that are on either side, near the back of the connector as that is where the slot would go.

        Virtually zero cost to add, other than the slight bump on the PC fab costing for the extra holes.

        • R0B0T1CS / about 9 years ago * / 1

          As long as the SMD pads are reinforced with, decently sized, vias, the most your should need is a little extra solder.

      • ElectronicAussie / about 9 years ago / 2

        There is an incredibly large range of options available for micro USB connectors, and the Sparkfun's choice in this case is well known for being the weakest and highly prone to failure.

        As this is a hobby product that is definitely going to get a lot more use and abuse than your average consumer product, I would expect a company like Sparkfun to make a more suitable choice. It's just not rocket science.

        A very simple and easy step forward towards a more robust product is to use a connector which is exactly the same as the one you're using except with shell through hole mounts. The cost of the connector is virtually identical. Obviously it adds a through hole step to your production process, but if that adds an extra dollar or two to the product cost then so be it. I certainly won't complain.

      • bmarvo / about 9 years ago / 2

        I've been using mid-mount micro USB connectors recently:

        They're pretty tough! Of course they do take a tad bit more board area

Customer Reviews

4 out of 5

Based on 4 ratings:

Currently viewing all customer reviews.

1 of 1 found this helpful:

Works great but hard to switch voltage

The board can switch between 3.3v and 5v output, but only if you cut the contact on the bottom and solder on your own switch. It was very difficult to do this. I followed the advice of one of the commenters and hot glued a tiny switch to the bottom.

It can power my ESP8266 board on its own

Four stars because I think it's probably just as good or better than the other FTDI breakouts on the site

2 of 2 found this helpful:

It works

It works great.

Not immediately obvious is the need to scrape off the VCC connection from 5V and then solder the 3.3V onto it.

To program the microcontroller, I used these connections: (Sparkfun board) -> (Atmega328P Microcontroller) // VCC->VCC // GND->GND // RX->TX // TX->RX // DTR->0.1uF Cap->Reset pin

Works well

I am pleased that the drivers work with my desktop processor, unlike the previous FTDI cable.

0 of 1 found this helpful:

Works great

Bought this to program my pro mini using a micro-usb connector, got it going without issues on both Windows and Linux (CentOS 6).

Do feel like it could be a bit cheaper, though.