Apple Watch Kobo Page Turner

Page turning remotes are great, but why buy a new thing to lose if you already have a perfectly capable device on your wrist?

Simply turn the crown to change pages, or use a pinch gesture on supported devices (Series 10 or newer). You'll get some gentle haptic feedback so you can manage all this without looking at your watch (or taking it out from under the covers).

Limitations

This app is very much in beta. I had to reverse engineer a fair amount of Kobo Bluetooth code, and there may still be bugs. Please file an issue if you hit something!

The Kobo code was built for MediaTek-based devices (Clara BW/Colour, Libra Colour, Elipsa 2E) and will not work on others. It probably would be straight forward to implement for older devices, but I do not have one around to build/test on.

Installation

Kobo

This produces KoboRoot.tgz containing both the plugin and BLE peripheral.

1. Connect Kobo via USB
2. Copy KoboRoot.tgz to the .kobo folder on the Kobo
3. Eject and reboot — files are installed automatically
4. Enable Bluetooth in Kobo settings

Apple Watch

Open KoboRemote.xcodeproj, build and install the Watch app target. It should connect automatically. There's also a Next Page control center widget, so that Apple Watch Ultra users can set up their action button to open the app and advance the page.

Uninstall

Create /mnt/onboard/.kobo-ble-remote-uninstall and reboot.

How it works

Kobo-btpt and the page turner Kobo sells work by communicating as Bluetooth peripherals. However, Apple's Core Bluetooth library does not allow Apple Watch to act as a peripheral. This plugin allows the Kobo to act as a Bluetooth peripheral, thereby enabling an Apple Watch to communicate with it (ie as a BLE central).

Apple Watch App

The WatchOS app is a super basic implementation of a BLE central.

There is a substantially identical iPhone app for testing purposes (ie because developing on Apple Watch is slow and annoying).

BLE Peripheral (kobo_bt/ble_peripheral.c)

Standalone binary running on the Kobo. Reverse engineers the MediaTek BT middleware (libmtk_bt_service_client.so) via dlopen to run the Bluetooth advertisement, GATT server and page-turning service, etc. When it receives commands, it then forward them over a Unix socket.

NickelHook Plugin (kobo_bt/src/kobo_ble_remote.cc)

Shared library loaded into Nickel's process via NickelHook. Receives the commands and turns them into next/prev page events. It uses Nickel's power management to handle sleep, waking, etc.

Building

cd kobo_bt
docker run --rm -v "$(pwd)/..:/work" -w /work/kobo_bt ghcr.io/pgaskin/nickeltc:1 make dist

Produces KoboRoot.tgz in the project root.