The enclosure mounts to the stem of his bike. It houses an Arduino board with a data logging shield of his own design. That shield holds an SD card for storage, and breaks the other pins out as ...

and [Ray] provides a reference schematic and BOM to get you started. The Arduino is programmed to mimic a keyboard, so the datalogging is achieved by allowing the Arduino to ‘type’ the data ...

Here is a circuit diagram of the multifunction shield adopted from the web (updated a bit by me). Looking up the schematic ... (DATA_DIO, CLK_DIO, MSBFIRST, SEGMENT_SELECT[Segment] ); ...