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Description: Get your PIC or other uC talking to your computer fast and easy with this board! This is a small custom PCB developed to connect the UART on a microcontroller directly to the computer without the hassle of a MAX232 circuit. Almost all current computers (less than 10 years old) utilize a serial port based on the EIA-232 standard which operates from +/-3-12V rather than the RS232 standard of +/-12V. This board takes signals from the computer/microcontroller and correctly inverts and amplifies the serial signals to the EIA-232 standard. Works great up to about 38400bps. Originally designed to get Bloader working in a bread-board setup, we use our Shifter at 115200bps without problems.

Comes as a bag of parts kit and is easily assembled if you can follow the silkscreen indicators and have beginning experience with a soldering iron.

Checkout our soldering tutorial to assemble this device.


  • Qty 1 : DB9 Female Header
  • Qty 1 : 2N3904
  • Qty 1 : 2N3906
  • Qty 1 : 1N4148
  • Qty 5 : 10K Ohm
  • Qty 2 : 220 Ohm
  • Qty 2 : Basic LEDs
  • Qty 1 : 10uF
  • Qty 4 : 5" Wire

Dimensions: 1.25x1.15"

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Customer Comments

  • I’m kind of confused by the description. Does it work up to 115200 or 38400?

    • I second that. 115200 is needed (reliably) for my intended use. Not “maybe, sorta”.

      How about some clarification Sparkfun ?

  • I have connected it to Arduino Pro and can only receive from Arduino but would not transmit. Why? I’m going to send back this and ask about refund.

  • Will this work if supplied with 3.3V?

  • The design is pretty ingenious but shouldn’t that work only in half-duplex? If the RS-232 device is sending a 0x00 byte (ie TX stays at a positive voltage), wouldn’t the capacitor gets depleted if on the other end we’re setting our TX (RX on the schematic) low hence the device’s RX to +5V? Then the next “1” sent to the RS-232 would be 0V instead of -9V which seems rather problematic.

    It’s still of great help whenever there’s no MAX232-like ICs around but the description is misleading if it’s not equivalent

  • Will this work with the Wiznet Serial-to-Ethernet adapter for hooking up a microcontroller to the internet?

  • I currently use a windows slate for all my work but it doesn’t have a serial port. Could I use a USB to serial adapter cable to use this with my computer’s USB port?

  • There are part-numbers on the schematic (e.g. Q1, Q2, R1, etc) but they’re not on the PCB.

    What the hell?

    I want to bodge together a custom adapter that does TTL level-shifting (5v-3.3v), and I’m stuck following traces to figure out what is what.

    There is enough space on the board for part deliminators, and you have double-sided silkscreen (there is a logo on the bottom. and nothing else). Would it kill you to label stuff?

  • Need to have a version that fits inside the DE-9 shell. The board can fit between the 4 and 5 pin sodler cups on back of solder DE-9 connector (male or female).
    An SMT MAX232 could then fit as well !!

  • I just spent several days trying to figure out a problem with a data communication project. It was traced back to this level converter. As mentioned/quoted by Paradoxial this type of “voltage stealing” converter may not work particularly well in all situations. Using a “real” level converter (using something like a Maxim 232 chip) might be a safer bet.
    I love Sparkfun products, but this is one I can’t fully recommend. It worked OK on an Arduino but not on other projects.

  • If I’m using this to connect a 5v Arduino Pro with a device that expects the full +/- 12V, should I set Vcc to 12V, or to 5V?

  • Note that if your serial signals are 3.3V, and you supply the board with 5V, your logic “1” will probably not be high enough to fire.

    • RussNelson:

      I need to convert from PC RS-232 signals to a device that can take 3.3V. I can only power the Shifter board with 5V. Are you saying that it’s not going to wrok? Has anybody tried it under these conditions?

  • Would this allow me to connect an openlog directly to a serial port to replace a serial printer?

  • Yes it works… I tested it! It works with 3.3V the same well as 5V!

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