Arduino Compatibility

Adding Arduino Symbols to Applications and Libraries

The Arduino SDK has a release cycle that is independent from Particle firmware. When a new Arduino SDK is released, the new APIs introduced will not be available in the Particle firmware until the next Particle firmware release at the earliest.

However, this does not have to stop applications and library authors from using these new Arduino APIs. In some cases, it's possible to duplicate the sources in your application or library. However, it is necessary to be sure these APIs defined in your code are only conditionally included, based on the version of the Arduino SDK provided by Particle firmware used to compile the library or application.

For example, let's say that in Arduino SDK 1.9.5, a new function was added, engageHyperdrive(). You read the description and determine this is perfect for your application or library and that you want to use it.

In your application sources, or library headers you would add the definition like this:

// Example of adding an Arduino SDK API in a later Arduino SDK than presently supported
#include "Arduino.h" // this declares that our app/library wants the extended Arduino support

#if ARDUINO < 10905   // the API is added in SDK version 1.9.5 so we don't re-define it when the SDK already has it
// now to define the new API
bool engageHyperdrive() {
   return false;  // womp womp
}
#endif

In your source code, you use the function normally. When compiling against a version of firmware that supports an older Arduino SDK, then your own version of the API will be used. Later, when engageHyperdrive() is added to Particle firmware, our version will be used. This happens when the ARDUINO version is the same or greater than the the corresponding version of the Arduino SDK, which indicates the API is provided by Particle firmware.

By using this technique, you can use new APIs and functions right away, while also allowing them to be later defined in the Arduino support provided by Particle, and crucially, without clashes.

Note: for this to work, the version check has to be correct and must use the value that the Arduino SDK sets the ARDUINO symbol to when the new Arduino API is first introduced in the Arduino SDK.