Common Guidelines across Levels

Heirachy of inclusion

Explanation

Arrows indicate which levels can include from. For example, L2_HAL can include L1_Peripherals, and L3_Application can include L2_HAL. L3_Applications should refrain from including L1_Peripherals. If an L3_Application needs to include from L1_Peripherals, it must only take the peripheral interface and not a specific platforms driver. L0_Platform 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 L1_Peripherals or even L2_HAL. There may be consideration in the future to seperate 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.