AMiRo-OS

About & License

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

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@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.

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

Contents

========

1.  About the Project

2.  File Structure

3.  Developer Guides

    1.  Adding a Device

    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 unsed and configured 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), on the other

hand 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

further configure individual drivers, the project expects an according file

"alldconf.h" to be found in the include paths when compiling the drivers.

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 `amiro-lld.mk` that allows to easily integrate the project.

    Furthermore, two interface headers are provided: amiro-lld.h and periphALh.

    *   `./docs/`  

        UML graphs (using PlantUML; see <https://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 contain various versions of a driver

        (e.g. `v1/`, `v2/`, etc.). By convention, the root directory of a driver

        is named by the exact product 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 paths to

        the `AMIROLLD_INC` variable and all C source files to the

        `AMIROLLD_CSRC` variable.

    *   `./templates/`  

        AMiRo-LLD expects a configuration header file "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

        interface header in the root directory (`./periphAL.h`) provides all

        required information for an implementation.

3 Developer Guides

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

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

guides in this chapter 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 in-depth 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 a 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 device `DEVICE1234`. The folders to be created in this case are hence

`./drivers/DEVICE1234/` and `./drivers/DEVICE1234/v1/`. In case there already

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

another version, the version subfolder must be named accordingly (e.g.

`./drivers/DEVICE1234/v2/`).

Most drivers will consist of exactly three files:

*   alld_DEVICE1234.mk

*   alld_DEVICE1234.h

*   alld_DEVICE1234.c

Some drivers, however, may feature multiple header and/or source 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 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 driver.

3.2 Implementing a Driver

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

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

probably start with 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 directly to interact with the

hardware or the operating system! For your driver, there is no knowledge about

the world beyond periphAL. If periphAL does not provide the functionality you

need, you should do 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 all required functions using periphAL.