Adds a draft document with instructions to contributors that develop a new hardware component

doc/source/developing_hardware_components.rst

+Software interface to new hardware components
+=============================================
+
+*** DRAFT VERSION - TO BE REVIEWED *
+This section is intended for developers of a new hardware component as part of an OhmPi system.
+
+It presents some advices and best practices that should help developing new hardware components to work
+within an OhmPi system.
+
+OhmPi is an open source system and contributions in terms of hardware and software are welcome. However, in order to
+maintain the project on tracks and promote exchange and reuse, it is necessary that contributors
+Developing a new hardware component is
+
+Two cases should be distinguished when dealing with hardware development components:
+1- Hardware component development that complies with the way the OhmPi Hardware System works. This means that this development
+focuses on improving a component (reduce cost, improve performance, adapt range to specific applications,
+design with easily available parts...). The created hardware component will expose the minimal functionalities required
+by hardware_system for this type of component.
+
+2- Hardware component development that introduces changes in the way the OhmPi Hardware System works. This means that
+the development does not only focus on improving a single component but also on the way to operate the system. A
+discussion with developers of the OhmPi_Hardware and OhmPi classes should be initiated at a very early stage to investigate
+the best ways to design and implement a working solution.
+
+If you are dealing with case 1 or have designed a development path and strategy, you are ready to start.
+
+First the hardware board/device should be conceived and designed. The Ohmpi team recommends that contributors design or
+import their boards within KiCAD and that both schemas and PCB are shared.
+
+When developing a new component Class, always start your development in a new branch.
+1- Create a new python file or make a copy and modify an existing similar component file.
+In this python file Create a new class based on the relevant abstract class of abstract_hardware_components.py.
+Implement the abstract methods to interact with your hardware. Name the file according to the name of the component.
+Place it in the ohmpi/hardware_component directory.
+
+2- Create a new configuration file or make a copy and modify of an existing configuration file.
+In this file describe you system including the new component in the HARDWARE_CONFIG dictionary.
+Name it config_XXX.py where XXX should be replaced by an expression describing the system.
+Place it in the ohmpi/configs directory.
+
+3- Create a new script or make a copy and modify of an existing script for testing the component.
+In this script write python code where you will conduct the tests of the required functionalities of the new component.
+