Common Guidelines across Levels

Hierarchy of inclusion

Explanation

Arrows indicate which levels can include from. For example, devices can include peripherals, and systems can include devices.

systems should refrain from including peripherals. If an systems needs to include from peripherals, it must only take the peripheral interface and not a specific platforms driver. platforms can include everything, except testing libraries, as its startup may need code from any of the levels. In order to hit the light weight goal, keep the code in startup to an absolute minimum.

Everything can include from utility/ and third_party/. Although, some third party libraries should not be included in some library code levels. For example, microrl, used for command line control, should not be included in anything in peripherals or even devices. There may be consideration in the future to separate the third party libraries into their own set of levels that match the library levels.

This approach is meant to keep a levels of isolation between the categories of files. Doing this can keep from circular dependencies and unreasonable coupling between the layers.

Utilities are meant to be usable on all levels.