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Arduino Pro Mini 328 - 3.3V/8MHz

Replacement:DEV-11114. The new version of the Pro Mini breaks out the ADC 6 and 7 pins! This page is for reference only.

It's blue! It's thin (0.8mm)! It's the Arduino Pro Mini! SparkFun's minimal design approach to Arduino. This is a 3.3V Arduino running the 8MHz bootloader (select 'Arduino Duemilanove w/ 328' within the Arduino software). Arduino Pro Mini does not come with connectors populated so that you can solder in any connector or wire with any orientation you need. We recommend first time Arduino users start with the Uno R3. It's a great board that will get you up and running quickly. The Arduino Pro series is meant for users that understand the limitations of system voltage (3.3V), lack of connectors, and USB off board.

We really wanted to minimize the cost of an Arduino. The Arduino Pro Mini is like the Arduino Mini (same pin out) but to keep the cost low, we used all SMD components, made it two layer, etc. This board connects directly to the FTDI Basic Breakout board and supports auto-reset. The Arduino Pro Mini also works with the FTDI cable but the FTDI cable does not bring out the DTR pin so the auto-reset feature will not work.

Not sure which Arduino or Arduino-compatible board is right for you? Check out our Arduino Buying Guide!

**Note: **A portion of this sale is given back to Arduino LLC to help fund continued development of new tools and new IDE features.

  • ATmega328 running at 8MHz with external resonator (0.5% tolerance)
  • Low-voltage board needs no interfacing circuitry to popular 3.3V devices and modules (GPS, accelerometers, sensors, etc)
  • USB connection off board
  • Supports auto-reset
  • 3.3V regulator
  • Max 150mA output
  • Over current protected
  • Reverse polarity protected
  • DC input 3.3V up to 12V
  • On board Power and Status LEDs* 0.7x1.3" (18x33mm)
  • Less than 2 grams


Arduino Pro Mini 328 - 3.3V/8MHz Product Help and Resources

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February 22, 2016

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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.

  • I received mine last week and am quite please, but I would like to comment on the awkward placement of the I2C lines. Considering the large number of these you have in stock, I won't suggest you run out and redesign the board, but please consider in the future revising the board to make these pins more easily accessible for those of us doing breadboard prototyping.

  • In the SparkFun Eagle library, the schematic and board layout are missing 2 pins, A4 and A5. Also would it be possible for there to be e schematic and board layout that included the serial programming pins?

  • Can someone clarify what voltage regulator was used? The implication is that it can drive up to 150mA with an input voltage up to 12V. I'm using it to drive a 75mA GPS module from the VCC pin and its is getting pretty toasty. RAW voltage is 12V, so (12V-3.3V)*150mA = 1.3W dissipation. Ouch.

  • Would it be possible to connect three 5V analog accelerometers (say the adxl193) and a 3.3V sensor stick simultaneously to my 3.3V Arduino Pro MIni? I'm planning on using a NCP1400-5V Step-Up breakout board to input 5V to my analog accelerometers. I have previously implemented this combination successfully on my Arduino Uno board, clearly I did not use the 5V Step-Up as the Arduino Uno provides a 5V output.

  • Can I program this board using the pins of an Arduino Uno board as explained in the 5V version? Not sure since this one is 3.3V...

  • Has anyone been able to get the Wire library to work on this board? I looked in the code and Wire’s twi.h file use 16Mhz as a #define, and changing it to 8MHz does not work.

    • I would also very much like to know if the Wire library works! I have just ordered this board (3v3 8MHz) and was planning to use it with an application of mine which relies on the Wire library for I2C communication.

      • Not sure what's going on with your setup RyanW (I2C can be tricky to get working depending on what you're talking to), but I've used the Wire library on these without issues a number of times.

  • This seems to work fine running straight off of a LiPower (3.7V-3.8V) battery. Is there any reason why this is a bad idea?

  • It would be awesome if you guys broke out the A4 and A5 pins onto the side of the board for I2C communication. It's a total hassle using this with a breadboard if you need I2C.

  • WAAAAAYYYY better than the Lilypad. Would choose this one every time.

  • is it OK if i power this with a 9 volt battery clip, or do i hame to use a regulated 5 volt power supply? please respond.

  • The pinout on the short end of the board is different in the first two photos. Can someone clarify which one is correct? Was there a pinout change at one point, or perhaps the silkscreen was wrong at one point?

  • Is it possible to convert this board to run 5v? I have a 3.3v board that I'd like to run in a 5v application. Is the difference between the two boards the regulator?

    • Yes, the regulator is the only difference. (This is a good reason to use sockets on your modules, you never know when you might want to swap one out.)

  • does anybody know if I need a pulldown resistor for a digiital output pin to make sure its 0v?

  • In case anyone wonders about the size, my sample is 18.25 mm x 33.32 mm x 2.60 mm. The tallest parts are two caps, then the button. If you removed the caps and the reset button, the height would be 2.03 mm (due to the CPU). The PCB itself is 0.94 mm (37 mils) thick.

  • can i get Arduino Pro Mini with the output pins soldered?

  • Can someone give me a part # for the crystal being used on this board? I can only find a 16MHz version (eg: CSTCE16M0V53).

  • For Arduino 0020 and later you should select 'Arduino Pro or Pro Mini (3.3V, 8 MHz) w/ ATmega328' for this board, not what it says in the description. Otherwise things like timing and serial rates will be half what you expect.

  • I'm hoping to use this board for a host of things but as a first I wanna ditch my stupid fan controller on my PC and use this. Bi-directional comms between this and the computer using just strings (of course some interpretive coding on the computer). Can I just do a quick and dirty resistor (68ohm in diagram on this site) line into the D+ and D- from two of the I/O lines? As power regulation is built on to the board.
    What is your recommended comm method? HID?

  • I want to run this arduino with coin cells. Two 3V cells in row would supply 6V... So am I right that the arduino can handle this if I connect the batteries to its 3.3V input?
    PS. I know those cells wouldn't last for long but that's not necessary.

    • You could probably get away with running the board one a single 3v cell.

      • I am thinking to an rechargeable coin cell(3.6v) too. Should I connect it to RAW or to VCC. If I make my own board I really need the voltage regulator, or I can use the battery directly to the system? I need to work with BMP085 sensor pressure witch is working at min 1.8v and the Atmega328 is working the same too.
        Thank you,

  • I have just ordered two Arduino Pro Minis 3V modules, but if it was possible I would have bought only the ATMega168 SMD chip with bootloader and developed my own board. If you start selling the chip with bootloader only, I probably would buy a couple!

  • Does anyone know if the inputs can handle 5v?
    The specsheet says Vcc + 0.5v.
    Vcc being 1.8 - 5.5.
    Does this mean that running Vcc at 3.3v, the inputs are tolerant of ~6v MAX? so 5v would be fine? or does this mean that the inputs can take 3.8v MAX?

  • I'll throw my support in making A4-A7 available on a breadboard. It also makes things easier if you're designing boards for the Pro Mini to mate with.
    Also, clarification:
    Are there components on this board that aren't rated for 12V+? The MIC5205 datasheet and the circuit schematic both list 16V as Vmax, but this page says 12V.
    Thanks! :)

  • I have bought several of these boards (mostly the 168 version) and they are great. However, I really hate the placement of the ADC pins A4 and A5. These 2 pins are used for I2C which I use (BlinkM, digital compass, EEPROM, etc) and it is awkward to use this on a breadboard. Also this chip supports 2 additional ADC (A6 and A7) which are not accessible. Any thought to updating this board and making all 4 of these pins available for bread board use? Also, what about the 10 MHz version that is listed in the silk screen on the board?

    • I agree, please stretch the board by two pins in order to bring out A4:A7. Also do you plan on providing the 20MHz version?

  • 0017 is out and supports the board, and at the correct baud rate.

  • Arduino 0016 is out now and supports this board, but the serial stuff runs at double speed (e.g., Serial.begin(9600) will actually result in 19,200).

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