computer science

OpenXC

OpenXC is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand OpenXC rather than just read about it. In short: OpenXC is a hardware and software API for automobiles developed by Ford Bug Labs and proposed as an open standard. At this time, the API is read-only (unlike the OBDII interface) and provides a small number of vehicle measurement parameters only (Engine speed, Vehicle speed, GPS position etc.).

Key takeaways

OpenXC belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect OpenXC to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of OpenXC from memory before moving on to harder problems.

Reference excerpt

OpenXC is a hardware and software API for automobiles developed by Ford Bug Labs and proposed as an open standard. At this time, the API is read-only (unlike the OBDII interface) and provides a small number of vehicle measurement parameters only (Engine speed, Vehicle speed, GPS position etc.).

History March 2012: Beta program announced 9 January 2012: OpenXC Platform Released

Architecture A typical implementation uses the following architectural layers:

Vehicle electronic control units CAN Bus OBDII Interface OpenXC Vehicle interface Module OpenXC wire messages over USB or Bluetooth OpenXC driver or service on a device (currently Android) E.g. OpenXC Enabler app for Android. OpenXC enabled applications. See Android sample applications: retro-gauge and mpg. Not all these layers are necessary, e.g. a vehicle might implement a native CAN Bus interface to USB or Bluetooth, without using the OBD socket or the reference OpenXC Vehicle interface Module. Or an alternative to the reference OpenXC Vehicle interface Module could be developed with a common ELM327 interface.

API The data available via the API as at January 2012 includes

AcceleratorPedalPosition BrakePedalStatus EngineSpeed FineOdometer - a persistent odometer recording) FuelConsumed - fuel consumed since the vehicle was started) FuelLevel - current level of fuel in the gas tank. HeadlampStatus - are headlamps are off or on. HighBeamStatus IgnitionStatus Latitude Longitude Odometer ParkingBrakeStatus - is the parking brake is engaged or not. SteeringWheelAngle TorqueAtTransmission - the actual current torque in the transmission. TransmissionGearPosition - the actual current gear of the transmission. TurnSignalStatus VehicleButtonEvent A ButtonEvent represents a button press, release or hold on the vehicle HMI. VehicleDoorStatus - is a door ajar? VehicleSpeed - the current forward speed of the vehicle. WindshieldWiperStatus

OpenXC Vs OBD Any information available from the current OpenXC API (and much more) is available from the OBD interface. However the core OBD standard is concerned with the engine train, emissions and faults (much more data is available through custom PIDs) while OpenXC is focused on high-level instrumentation of more interest to a driver. The potential advantages of using OpenXC include

Most useful information available from OBD interfaces uses proprietary PIDs that may differ by manufacturer and Vehicle. OpenXC could offer a standard interface, similar to the ELM327 interface. An OBD interface may be complex to implement, while the OpenXC API is designed to be friendly for application developers Possible advantages of using the OBD interface include

Use well established existing OBD interface hardware and software, e.g. using the ELM327 protocol The additional hardware layer for OpenXC is currently much more expensive than OBD interfaces Access additional functions than the limited set available via OpenXC. E.g. manifold vacuum (OBD PID 01-0B). Few vehicles currently support OpenXC (8 Ford models as at January 2013), while nearly all modern vehicles support OBD Ability to write data back to vehicle, e.g. to clear fault codes.

See also On-Board Diagnostics OBD-II PIDs Arduino OBDuino ELM327 Trip computer Carputer

References

Worked examples

Example 1 — a first encounter with OpenXC

Start with the simplest possible case. Write down what OpenXC claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to OpenXC before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about OpenXC ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of OpenXC

In research: OpenXC appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses OpenXC in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: OpenXC is common in secondary-school and first-year university syllabi. It links to neighbouring topics Automotive software, so understanding it makes those chapters shorter.
In everyday life: Look for OpenXC outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study OpenXC in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what OpenXC means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain OpenXC out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is OpenXC in simple terms?

Why does OpenXC matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study OpenXC?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on OpenXC.