You are reading a single comment by @yoshy and its replies.
Click here to read the full conversation.
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
@yoshy
Di2 runs on CAN bus, so is most likely a really dumb microcontroller in a low power state waiting to be brought out of it if an input (attached to the shift lever) changes. If it does, it sends the CAN message to the derailleur and it's done.
Edit: CAN bus is the main comms protocol used in cars in case anyone's interested