AMiRo-OS

AMiRo-LLD is a compilation of low-level hardware drivers for the base version of

the Autonomous Mini Robot (AMiRo) [1]. It provides directional interfaces for an

operating system to access the drivers and for the drivers to access the

communication infrastructure via the operating system.

Copyright (C) 2016..2020  Thomas Schöpping et al.

(a complete list of all authors is given below)

This program is free software: you can redistribute it and/or modify

it under the terms of the GNU Lesser General Public License as published by

the Free Software Foundation, either version 3 of the License, or (at

your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License

along with this program.  If not, see <http://www.gnu.org/licenses/>.

This research/work was supported by the Cluster of Excellence

Cognitive Interaction Technology 'CITEC' (EXC 277) at Bielefeld

University, which is funded by the German Research Foundation (DFG).

Authors:

 - Thomas Schöpping          <tschoepp[at]cit-ec.uni-bielefeld.de>

 - Marc Rothmann

References:

 [1] S. Herbrechtsmeier, T. Korthals, T. Schopping and U. Rückert, "AMiRo: A

     modular & customizable open-source mini robot platform," 2016 20th

     International Conference on System Theory, Control and Computing (ICSTCC),

     Sinaia, 2016, pp. 687-692.

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This file provides information about the purpose of this project, the file

structure and some helpful guides for development of code.

================================================================================

CONTENTS:

  1  About the Project

  2  File Structure

  3  Developer Guides

    3.1  Adding a Device

    3.2  Implementing a Driver

================================================================================

1 - ABOUT THE PROJECT

=====================

AMiRo-LLD is a compilation of low-level hardware drivers, originally developed

for the Autonomous Mini Robot (AMiRo) [1]. It provides a modular design, so that

each driver can be activated individually as required. Interface functions allow

for bidirectional comunication with an operating system. On the one hand drivers

access according hardware interfaces via defined interface functions (which need

to be implemented by the operating system) and any applications (or the

operating system itself) can take advantage of the drivers by their individual

interfaces. The abstraction layer of the hardware interfaces is called

"periphAL", which is defined by this project. In order to configure which

drivers should be used in which version, the project expects an according file

"alldconf.h" to be found in the include paths.

Although this compilation was originally designed to be used in combination with

the AMiRo operating system (AMiRo-OS; cf. https://opensource.cit-ec.de/projects/amiro-os/),

it is not limited to this use case. The included drivers may be used for any

purpose and contributions of further drivers, even if the according hardware is

not present on the AMiRo platform, are highly appreciated.

2 - FILE STRUCTURE

==================

The files are structured as follows:

./

│ The project root directory contains this file, a license.html file as well as

│ a makefile that allows to easily integrate the project. Furthermore, two

│ interface headers are provided: amiro-lld.h and periphALtypes.h. These are

│ entry points for any utilizing superproject, so it is not required (and not

│ recommended) to include each driver individually.

│

├── docs/

│     UML graphs (using PlantUML; see plantuml.com for further information)

│     visualize the structure of the AMiRo-LLD project. Doxygen related files

│     can be used to gererate a documentation of the whole project (wip).

│

├── drivers/

│     For each supported hardware device, there is exactly one directory in this

│     folder. Further subfolders may contain various versions of a driver (e.g.

│     'v1/', 'v2/', etc.). By convention the root directory of a driver is named

│     by the form

│     "<product_name>/"

│     <product_name> is a placeholder for the exact name of the according

│     hardware, or the product familiy, if the driver is compatible with all

│     parts.

│     Each driver must provide a makefile script, which adds the required

│     include folders to the AMIROLLD_INC variable and all C source files to the

│     AMIROLLD_CSRC variable.

│

└── templates/

      AMiRo-LLD expects a configuration header "alldconf.h" to be found in the

      include paths. An according template for such file can be found here.

      There is no template for an implementation of periphAL, though. The

      provided interface header in the root directory (periphAL.h) should give

      you all required information for such an implementation anyway.

3 - DEVELOPER GUIDES

====================

In order to keep all code within this project as homogeneous as possible, the

guides of these chapters should help developers to achieve functional and clean

results, which are portable and maintainable for future use. Whereas the textual

descriptions of the guides provide additional information about the underlying

concepts and mechanisms, a short summary is provided at the end of each chapter.

3.1  Adding a Device

--------------------

When adding new device to the project, the very first step is to create the

according folder in the drivers/ directory. For this guide, we will add the

fictional DEVICE1234. For this example the folders to be created are

"drivers/DEVICE1234/" and "drivers/DEVICE1234/v1/". In case there already exists

a driver implementation for this device, but you want to implement another

version from scratch (not just an update), the version subfolder must be named

accordingly (e.g. "drivers/DEVICE1234/v42/").

Most drivers will consist of exactly three files:

 - alld_DEVICE1234.mk

 - alld_DEVICE1234.h

 - alld_DEVICE1234.c

However, some drivers may feature multiple .h and/or .c files or even come with

additional subfolders. In any case, all those required folders, including the

driver root folder (i.e. "drivers/DEVICE1234/v1/"), as well as all C source

files must be added to the according makefile variables AMIROLLD_INC and

AMIROLLD_CSRC by the makefile script.

It is highly recommended that files in the driver root directory (i.e.

"drivers/DEVICE1234/v1/") use the prefix "alld_" in their names. This not only

helps to achieve an easy to understand file structure, but also prevents

compilation issues due to naming conflicts of header files.

Summing up, you have to

1) create device and version folders.

2) add a makefile script.

3) add header- and source files as well as subfulders, implementing the diver

3.2  Implementing a Driver

--------------------------

Implementation of a new driver usually is very straightforward. You most

probably have a comprehensive datasheet of the device, or the manufacturer even

provides a reference driver implementation.

For the former case, you should first write a comprehensive header, containing

all information like constants, register maps, etc. and according abstract

access functions (e.g. for reading and writing registers, and convenient access

to common functionalities). Only then you implement those functions, using

periphAL to interface any hardware interfaces (e.g. I2C, SPI, etc.) in a

separate C source file, or 'inline' in the header file itself.

For the latter case, the reference implementation will specify some interface

functions to interact with the hardware (e.g. I2C, SPI etc.). Even though all

functionality should be covered by the reference driver, you still need to

implement those interface functions and map them to periphAL.

Since AMiRo-LLD does not rely on specific hardware or operating system, the only

valid way to interact with both is through periphAL. Under no circumstances you

must use any function of your operating system and directly or indirectly access

the hardware of your platform. For your driver, there is no knowledge about the

world beyond periphAL! If periphAL does not provide the function you need, you

can do one of the following:

1) Think again if you really need that funcionality or whether it can be

   replicated by the existing API.

2) File a feature request to extend periphAL.

3) Write a custom patch that modifies periphAL to meet your requirements.

Summing up, you have to

1) Get and read the datasheet of the device (A) or

   acquire a copy of the reference implementation (B).

2) Case A: define constants, register map and access functions in a header file.

   Case B: identify the interface functions of the reference implementation.

3) Implement the missing functions using periphAL.

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