Walter is a proof of concept SDK for BMWs utilising I/K-BUS. It includes resources for developing and deploying software plugins, a high level API (audio, communications etc), and lower level module APIs (radio, onboard-monitor interface etc).
This is not, and should not be considered a library (hence the absence of a published gem), nor a how to guide. Although, I plan to continue developing the underlying library- albeit, to suit my needs, and general philosophy.
Relative to the project, the underlying library is over engineered (over complicated?), but a large part of my interest was in developing a flexible and extensible tool kit, for which this project was the first use case.
Walter began as a means to add support for Bluetooth audio (A2DP/AVRCP) with native display, and control via the on-board monitor (BMBT), and multi-function steering wheel controls (MFL) to my BMW E39 5 series. In my case, a 1997 528i Touring, optioned with navigation, HiFi, and telephone (i.e. High IKE, with both I and K buses).
There are a number of products available that fulfil this need, but each had compromises, and I was curious to what functionality could be developed via the I/K bus.
Like the Intravee, and a number of other projects, I planned to replace the CD changer, and emulate it's behaviour as to retain the native interface and controls. This began in earnest, and would come to work well for the best part. However, the solution also required a number of compromises that left me a little dissatisfied, the root of which was maintaining support for the factory audio and communication system.
Given the increasing- if not complete obsolescence, of said systems, I decided to remove the legacy modules entirely, and write an API that would allow me to retain and repurpose the existing human interfaces while adding my own functionality. I also stripped the redundant wiring from the vehicle wiring harness, so there was no turning back.
- Raspberry Pi 3 Model B
- Resler USB v6b Interface
- Bluetooth v4.0 USB module (CSR8510)
- Audio circuit: 3.5mm stereo pigtail and mish-mash of breadboard, jumper wires etc.
- Auto power on circuit: as above, plus opto-isolator, resistor etc.
- Raspbian: Stretch running headless for a rather swift boot
- Bluez: the Linux Bluetooth stack
- PulseAudio (with Bluetooth modules)
- Wolfgang (see below)
Walter relies upon a library wilhelm, which is broken into several sub-libraries:
| Library | Description |
|---|---|
wilhelm-core |
is akin to the first, and second layer of the OSI model. The lower of the two layers encapsulates IO operations for the bus, while higher of the two layers handles frame synchronisation, and error detection. |
wilhelm-virtual |
is a model of the bus, and common devices. This allows for building device specific states, and APIs, and acts as a framework for implementing either emulated modules i.e. the radio when it has been removed, or augmented modules i.e. piggybacking the graphics stage. |
wilhelm-api |
is a high level API with abstractions of vehicle features, i.e. audio, telephone, display. The API objects are designed to be universal (i.e. communication, music, navigation), reflect common operations, e.g. API::Telephone.incoming_call(caller_id), and remain agnostic, thus removing the need to deal with the intricacies the bus. |
wilhelm-sdk |
is a small MVC framework, and runtime environment for services, and built on top of wilhelm-api. The runtime environment includes a messaging queue (via wilhelm-tools), for inter-process or network communication with supporting services. |
wilhelm-services |
includes a simple Bluetooth device manager, and Bluetooth audio streaming, two examples of services built, and deployed using the wilhelm-sdk library. They act only as an abstraction for a Bluetooth car kit with Bluez doing the heavy lifting with a little help from Wolfgang, which encapsulates the Bluez D-BUS API, and implements a virtual car kit |
This program is released under the GNU General Public License v3.0.