Modern Di2 is basically a couple of controllers and motors that communicate with each other using the EW-SD50 wires. Shimano lets end-users configure their own Di2 systems using their e-tube project software. This page explains how to connect your bike to your computer.
Make sure you have either the SM-PCE1 diagnostics device or the SM-BCR2 charger. Also, download an up to date version of the e-Tube Project software. We recommend you use the computer software, not the mobile/tablet apps (they’re likely to crash and render your system unresponsive). Once you’ve installed the software you’re all set!
Connect using e-Tube Project
Plug your charger into the junction box and connect the other end to your computer – the order doesn’t really matter, but we tend to plug the connector into the bike first. Start the e-Tube Project software. Select your bike type (road, MTB, Urban/City, STEPS e-bike or ‘other e-bike’) system.
It’ll then tell you that charging has stopped because you’ve connected the bike to the computer and started the software.
If you’re using a road bike it will also ask you whether you’ve connected satellite shifters to your main shifters. Answer the questions and it’ll complete the connection.