Featherwings and Peripherals

Support for peripherals (e.g. Featherwings or the RFM95 radio on the radio-enabled Feathers) is done using the appropriate header under feather/wing. Generally, there are four steps to setting up wings:

  • Define all the wings as global variables to make them available throughout the code.
  • Register the wings using registerWing.
  • Call initialiseWings to run the wings’ setup functions. If any of these fails, they will print a message about the fault to the serial console and booting will halt.
  • Regularly run runWings; support for the Arduino SAMD scheduler is provided using scheduleWingTasks.

The FeatherWing base class

Every supported peripheral is an instance of the FeatherWing class. They provide three functions:

  • bool setup() runs any setup tasks; if setup fails, this will return false and a message about the fault is printed to the serial console.
  • void task() runs regular update tasks. For example, a GPS needs to regularly update itself to check for new data. These are written with the intent that they can be used in a cooperative scheduler; they won’t take over and block execution.
  • const char *name() returns the name of the FeatherWing.

The void registerWing(FeatherWing &) function, included in feather/wing/wing.h, will add the FeatherWing to the global registry. This registry is used for setting up the wings later on and for running update tasks.

Once the wings are all registered, bool initialiseWings() should be called to run the setup function on all the wings, called in the order they are registered. If any of the setup tasks fails, this will return false. The intent is to call something like the following in the setup function:

if (!initialiseWings()) {
        Serial.println("BOOT FAILED");
        while (true) ;

Finally, near the end of the setup function, void scheduleWingTasks() should be called - this will use the Arduino scheduler to run the wing update tasks in the background. Alternately, the function runWings() can be called regularly, e.g. in the main loop so long as there aren’t long delays. It may also be used with another scheduler or task management system; wing tasks are designed to be cooperative and each run of the function will run through the update tasks once. For schedulers that don’t treat tasks as loop equivalents, a wrapper function should be used, such as:

        while (true) {

The Clock abstract base class

Another base class is implemented in feather/wing/wing.h is Clock, which is meant to be used in defining realtime clocks (RTCs). A Clock provides two functions:

  • bool isClockReady() should return true if the clock has a valid time.
  • bool getDateTime(DateTime &dateTime) will return false if the clock isn’t ready or if an error getting the time occurs. Otherwise, the DateTime instance (this type is defined in RTClib) will be filled in with the current time from the Clock.

A helper function is also provided in feather/wing/wing.h for use with a Clock: bool clockFormatTime(Clock &clock, char *buf) wraps getDateTime, and if successful, fills buf with the time formatted as YYYY-MM-DD hh:mm:ss. The buffer must be large enough to support this, which is a minimum of 19 bytes.