Wednesday, November 19, 2014

A question of getting there

The third of a series of posts on the QNX CAR Platform. In this installment, we turn to a key point of interest: the platform’s navigation service.

From the beginning, we designed the QNX CAR Platform for Infotainment with flexibility in mind. Our philosophy is to give customers the freedom to choose the hardware platforms, application environments, user-interface tools, and smartphone connectivity protocols that best address their requirements. This same spirit of flexibility extends to navigation solutions.

For evidence, look no further than our current technology concept car. It can support navigation from Elektrobit:

from Nokia HERE:

and from Kotei Informatics:

These are but a few examples. The QNX CAR Platform can also support navigation solutions from companies like AISIN AW, NavNGo, TCS, TeleNav, and ZENRIN DataCom, enabling automakers and automotive Tier 1 suppliers to choose the navigation solution, or solutions, best suited to the regions or demographics they wish to target. (In addition to these embedded solutions, the platform can also provide access to smartphone-based navigation services through its support for MirrorLink and other connectivity protocols — more on this in a subsequent post.)

Under the hood
In our previous installment, we looked at the QNX CAR Platform’s middleware layer, which provides infotainment applications with a variety of services, including Bluetooth, radio, multimedia discovery and playback, and automatic speech recognition. The middleware layer also includes a navigation service that, true to the platform’s overall flexibility, allows developers to use navigation engines from multiple vendors and to change engines without affecting the high-level navigation applications that the user interacts with.

An illustration is in order. If you look the image below, you’ll see OpenGL-based map data rendered on one graphics layer and, on the layer above it, Qt-based application data (current street, distance to destination, and other route information) pulled from the navigation engine. By taking advantage of the platform’s navigation service, you could swap in a different navigation engine without having to rewrite the Qt application:

To achieve this flexibility, the navigation service makes use of the QNX CAR Platform’s persistent/publish subscribe (PPS) messaging, which cleanly abstracts lower-level services from the higher-level applications they communicate with. Let's look at another diagram to see how this works:

In the PPS model, services publish information to data objects; other programs can subscribe to those objects and receive notifications when the objects have changed. So, for the example above, the navigation engine could generate updates to the route information, and the navigation service could publish those updates to a PPS “navigation status object,” thereby making the updates available to any program that subscribes to the object — including the Qt application.

With this approach, the Qt application doesn't need to know anything about the navigation engine, nor does the navigation engine need to know anything about the Qt app. As a result, either could be swapped out without affecting the other.

Here's another example of how this model allows components to communicate with one another:
  1. Using the system's human machine interface (HMI), the drivers asks the navigation system to search for a point of interest (POI) — this could take the form of a voice command or a tap on the system display.
  2. The HMI responds by writing the request to a PPS “navigation control” object.
  3. The navigation service reads the request from the PPS object and forwards it to the navigation engine.
  4. The navigation engine returns the result.
  5. The navigation service updates the PPS object to notify the HMI that its request has been completed. It also writes the results to a database so that all subscribers to this object can read the results.
By using PPS, the navigation service can make details of the route available to a variety of applications. For instance, it could publish trip information that a weather app could subscribe to. The app could then display the weather forecast for the destination, at the estimated time of arrival.

To give developers a jump start, the QNX CAR Platform comes pre-integrated with Elektrobit’s EB street director navigation software. This reference integration shows developers how to implement "command and control" between the HMI and the participating components, including the navigation engine, navigation service, window manager, and PPS interface. As the above diagram indicates, the reference implementation works with both of the HMIs — one based on HTML5, the other based on Qt — that the QNX CAR Platform supports out of the box.

Previous posts in the QNX CAR Platform series:

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