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SparkFun OpenSegment Shield
project on project

DIY Breathalyzer
by Shawn hymel

Description: We love 7-segment displays and we know you do too, so we have made the easiest (arguably) to use medium for you to get up and running and use! This SparkFun OpenSegment Shield was specifically designed to run on top of most Arduino Uno compatible boards, all you need to do is attach headers and your choice of 7-segment display to the shield and snap it in, no bread boards required. The OpenSegment Shield can combine a classic 4-digit 7-segment display and an ATMega328 microcontroller allowing you to control every segment individually using only a few serial lines.

Just like our other 7-segment boards, the OpenSegment Shield can be controlled in one of three ways: Serial TTL communication, SPI serial communication or I2C serial. This shield is very similar to our other OpenSegment Displays, the biggest benefit to this board is its ease of use thanks to the Arduino Uno form factor.

Note: This does NOT include a 7-segment display. We’ve removed the display itself to give you a chance to choose a specific color. Check the Recommended Products section below for different options.


  • 4 digit alpha-numeric display area with Serial Comm, SPI or I2C Serial Interface
  • Display numbers, many letters, and a few special characters
  • Individual control of decimal points
  • Selectable baud rate
  • Selectable brightness
  • Baud rate and brightness values retained in non-volatile memory
  • Individual segment control for each digit
  • Arduino Uno Form Factor


Recommended Products

Customer Comments

  • A customer reported an issue requiring reflashing of the firmware. Here’s a tutorial on reflashing - - and the firmware is linked in Documents above. Check with our Tech Support if you have any questions.

  • When uploading the firmware I found that I needed to change line 39 of Serial_7_Segment_Display_Firmware.ino from: #define DISPLAY_TYPE OPENSEGMENT to: #define DISPLAY_TYPE S7SHIELD

    (Not that you need to upload the firmware. I wanted to add some things…)

  • This board is poorly designed. The ATmega328 controls the selected display directly, which means that a single pin will drive up to 8 LEDs simultaneously. Way too much current for that pin, and in the long term damage to the controller. In the next version of this board please include transistors for the digit pins.

  • Is the firmware for this similar, if not the same as, the original OpenSegment?

    • Is the firmware published anywhere?

      • Oops! The wrong GitHub link is listed above. It’ll be updated momentarily, and will have the library included in there.

        Edit: The board files are correct in the current link. We’ll still get the firmware linked. Sorry about the confusion!

  • Are the shields with the 7-segment display included on sale? This seems to be a couple of dollars more without the LEDs.

Customer Reviews

4.5 out of 5

Based on 2 ratings:

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1 of 1 found this helpful:

Excellent Hookup Guide(s)!

Great idea and easy to use. No problems to report. The highlight is the very complete Connection Guide: accurate and complete. I like these displays for debugging code, because i am too lazy to click and open the serial dialog. I have yet to hack the firmware, but that looks like it has endless possibilities as well.

Seems fine but doesn't work with all 7 segment displays...

I bought the shield several months after I bought the 7 segment display from SparkFun. I should have checked the recommended products (so this is almost totally on me), but this board only works with the 20mm 7 segment display, not the regular 7 segment display.

Oh well. I’ll just grab one next time I order from Sparkfun.

Related Tutorials

Using OpenSegment

April 1, 2013

How to hook up and use the OpenSegment display.