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MaRTE OS

    Minimal Real Time Operating System for Embedded Applications
                   Version 2.0 - Feb 2017

     Copyright (C) 2000-2017  Universidad de Cantabria, SPAIN

     Authors: Mario Aldea Rivas         aldeam@unican.es
              Michael Gonzalez Harbour     mgh@unican.es

Introduction

MaRTE OS is a real-time kernel for embedded applications that follows the Minimal Real-Time POSIX.13 [POSIX] subset. Most of its code is written in Ada with some C and assembler parts.

It allows software cross-development of Ada and C applications using the GNU compilers Gnat and Gcc. In particular in the case of Gnat the Run-Time Library (GNARL) has been adapted to run on our kernel. Remote debugging of applications is also possible using the GNU debugger gdb.

MaRTE OS supports two target architectures: x86 and Raspberry Pi (models 1 and Zero).

For the x86 architecture the MaRTE OS the cross environment is formed by a PC running Linux as "Host" and a bare x86 board as "Target", both systems connected by and Ethernet LAN (for application booting) and a serial line (for remote debugging).

MaRTE OS is developed by the Group of "Ingenieria Software y Tiempo Real" of the Department of "Ingenieria Software y Electronica" of the University of Cantabria. It is not a finished product, but we share it hopping it can be useful for educational or experimental purposes.

MaRTE OS is available under the GNU General Public License.

Functionality Implemented

MaRTE OS implements the following POSIX functionality:

  • Pthread Management (creation, finalization, attributes, ...).

  • Priority scheduling (FIFO, Round-Robin and Sporadic Server scheduling policies supported).

  • Mutexes and Condition Variables.

  • Semaphores.

  • Signals (partially implemented).

  • Clocks (monotonic and real time) and Timers.

  • CPU time Clocks and Timers.

  • Console I/O.

  • Time Services: absolute and relative tasks and Pthreads suspension.

  • Dynamic Memory Management.

This POSIX functionality support the whole gnat run time library, so the current MaRTE OS implementation allows running complex C and Ada applications which do not use a file system (limitation imposed by the Minimal Real-Time POSIX.13 subset).

Apart from the POSIX standard functionality supported, in MaRTE OS we have implemented some other features we consider very interesting for real-time systems programmers:

  • Application-Defined Scheduling:

MaRTE OS includes application program interfaces (API) that enables Ada and C applications to use application-defined scheduling algorithms in a way compatible with the scheduling algorithms defined in POSIX and in the Ada 95 Real-Time Systems Annex. Several application-defined schedulers, implemented as special user tasks, can coexist in the system in a predictable way.

  • Interrupts Management at Application Level:

MaRTE OS offers to Ada and C programmers an API that allows dealing with hardware interrupts in an easy way. Basically this API offers operations to: enable and disable hardware interrupts, install interrupt handler procedures and put tasks or threads waiting for a hardware interrupt.

  • Addings to POSIX:

Ada binding for CPU-Time clocks and access to the thread-specific data form a thread different from the owner.

Development Environment

MaRTE OS works in a cross development environment:

  Host                                                 Target
+-------------------+            Ethernet            +-----------------+
| Linux             |--------------------------------|                 |
| Gnat              |     (For booting purposes,     | i386 or above   |
| gcc               |    involves dhcpd and nfsd)    | Floppy Disk     |
| gdb               |                                |                 |
| MaRTE OS          |                                | Doesn't need HD |
| dhcpd (or bootpd) |            RS-232              | Doesn't need OS |
| nfsd              |--------------------------------|                 |
+-------------------+    (For debugging purposes,    +-----------------+
                              gdb is used)

Distribution Directory Overview

This is the top level of the MaRTE OS directory structure. The following is a description of the files and directories you will find in it:

  • INSTALL: Installation instructions.

  • README: This file.

  • arch: link to the directory of the active architecture ('linux_arch/', 'linux_lib_arch/' or 'x86_arch/')

  • arch/drivers/: code for some device drivers.

  • arch/include/: POSIX C header files.

  • arch/libmc/: libc implementation.

  • examples/: some simple program examples.

  • COPYING: The license used to distribute MaRTE OS code

  • kernel/ : source code for the hardware independent part of the kernel.

  • lib/: link to the object files and libraries directory of the active architecture ('objs/linux_lib_objs/', 'objs/linux_objs/' or 'objs/x86_objs/').

  • gnat_rts/: GNAT packages modified for MaRTE OS.

  • marte_ug.html: MaRTE OS User's Guide.

  • minstall: main installation script.

  • misc/: miscellany of utility packages.

  • objs/: object files and libraries directory.

  • posix5/: POSIX.5 packages (POSIX Ada bindings). Based on the Florist [Florist] implementation.

  • sll/: singly linked lists used by the kernel.

  • tasks_inspector/: a tool to analyze graphically the execution flow of a finished application.

  • utils/: compilation utilities.

  • x86_arch/: source code for the hardware dependent part of the kernel for 386 PC or above.

  • rpi_arch/: source code for the hardware dependent part of the kernel for Raspberry Pi 1 and Zero.

  • linux_arch/: source code for the hardware dependent part of the kernel to execute MaRTE OS as a Linux process.

  • linux_lib_arch/: source code for the hardware dependent part of the kernel to execute MaRTE OS as a Linux process with access to the Linux GLIBC library (including filesystem functions for example).

  • xtratum_arch/: source code for the hardware dependent part of the kernel for the XtratuM hypervisor.

  • tests/: a set of regression tests for MaRTE OS.

  • lang_support/: includes support libraries for other languages. For example, the runtime for C++ applications (libsupc++.a) and the C++ STL port library taken from uSTL.

References

[POSIX] IEEE Std. 1003.13-1998. Information Technology -Standardized Application Environment Profile- POSIX Realtime Application Support (AEP). The Institute of Electrical and Electronics Engineers, 1998.

[Florist] http://www.cs.fsu.edu/~baker/florist.html

[uSTL] http://ustl.sourceforge.net/

Contact Address:                          MaRTE OS Internet site:
aldeam@unican.es                          http://marte.unican.es

           Department of Ingenieria Software y Electronica
             Group of Ingenieria Software y Tiempo Real
                     University of Cantabria
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