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Welcome to the Flip Side Dio Development Site

The Flip Side Dio project is a DIY project for people that want to make a simple lap counter. In the past people would use the parallel port to build simple lap counters with cheap hardware but modern computers no longer have a parallel port. For our project we will use the  Arduino Uno hardware to build a basic lap counter. This hardware is very popular and well supported by the community. The  Flip Side Racing Software has built in support for the Dio hardware. An Arduino sketch is provided that can be uploaded to the Arduino Uno.

Design Overview

For our project we will use the Arduino Uno board as our platform. The Arduino sketch provided will detect any time one of the digital pins changes it state. If it goes from High to Low or Low to High it will transmit that pin number back to the computer so the Flip Side Racing software can detect laps. The pins are tied to an internal 20K ohm pull-up resistor so to detect changes your sensor or switch will need to be tied to the ground pin of the Arduino. The Arduino sketch looks for changes on digital pins 2 through 10.

Here is an example board layout that will detect when switches are pressed. Click on the image to see a larger version.


Here is the related schematic of the above board layout.


Using these examples I constructed a lap counter for a slot car track with switches in the track to detect the cars. Similar approaches could be used for RC vehicles by replacing the switches with sensors to detect a break in a laser beam or infrared light.

After you have built your hardware you will need to upload the  Flip Side Dio sketch and write it to the Arduino Uno. If you are unfamiliar with how to do this the  Arduino web site has detailed tutorials you can use such as the ones located in the  Getting Started section.

Help the project

If you find this project useful, please consider helping support its development and the related development of the Flip Side Racing software.


Flip Side Dio is released under the  Gnu Public License

You can download a zipped copy of the Arduino Sketch from here:

 Flip Side Dio sketch

To download the latest source code use the following path in your subversion client:

For example to use the command line subversion command line client type this command:

svn co

The source code includes the Arduino sketch along with an example Fritz diagram.