Mkernel - Kernel for PIC18Fx550 micro controler

1. Overview

   1. Introduction

   2. Architecture

   3. Application Interface

2. Development Environment

3. Contact

4. Accessing the Source Code

5. Some Copyrigth notices

Overview

Introduction

The Mkernel, Michaels Kernel, Mini Kernel, call it what you want, was created after porting FreeRTOS to a PIC18F4550 using the SDCC. The motivation for starting an independent development was the memory footprint, since FreeRTOS was when compiled with SDCC consuming 80% of the code space. So the basic idea of Mkernel is to keep requirements and implementation simple and small.

Besides the beeing simple, starting with Version 0.6.x the kernel API will be developed based along the OSEK/VDX specification since i like to reuse the mature semantics of the OSEK/VDX specifications as long as it creates no useless burden.  Specially the idea of leaving the creation of the complete system to tools  using a specification language  will become a key element of Mkernel.

Even thought, mkernel is not intended as a compliant OSEK/VDX implementation, it supports the following OSEK/VDX inpspired features:

• Extended Task Model

• Resources

• Counter & Alarms

• Process communication based on OSEK/VDX like event passing

• OIL Systembuilder

• Process/Interrupt handler communication based on events and resources.

• Simple device model

• Drivers for most of the build in devices of the PIC18f4550 (ADC,PWM,CVREF, I2C, COMP).

• Drivers for the IOR5E board

The project results maintained at source forge

Getting started with mkernel

The kernel it is implemented as a set of libraries which are linked with the application part.  Lets assume we like to write an application which is intended to toggle a led. The first thing you need is an alarm which fires regulary and a task which does the actual toggeling. 

The implementation of such a task rather straight forward:

static byte led_state = 0;

TASK(ToggelLED) {
        led_state = !led_state;
        if(led_state)
                led_on(1);
        else
                led_off(1);

        TerminateTask();
}


This task need to be associated with an periodic alarm. This is done by creating three entries in the system defintion file of the application. The following definitions do specify a counter which is associated with an alarm which activates the task ToggelLED.


        COUNTER ledCounter {
                MAXALLOWEDVALUE = 20;
                TICKSPERBASE = 10;
        } ;

        ALARM ledAlarm {
                COUNTER = ledCounter;

                ACTION = ACTIVATETASK { TASK = ToggelLED; };

                AUTOSTART = TRUE {
                        APPMODE = IOR5E;
                };
        } ;

The properties of the actual task need to be specified as well.

        TASK ToggelLED {
                PRIORITY = 1;
                STACKSIZE = 96;
                SCHEDULE = FULL;
                AUTOSTART = FALSE;
        };

Running the OIL compiler will provide the glue code needed to maintain the counters and the provide the task.

After linking the image it is loaded into the micro controler using e.g. a bootloader. 

The most simples way of getting started is to create a directory in the root directory of the mkernel installation and  copy the Makefile and a sample testx.c into this directory from the ./samples directory.

Application Interface

The API available to applications is described in the include file kernel.h. It provides task managemant and communication function which allows an task to event on external events and to send events to other tasks.

Bootloader

The project uses the bootloader fsusb from Rick Luddy. This seems to work well with the SBC44UCR board i am using. I have added the source code to the svn tree even thought i don't expect any changes.

Development Environment

The following tools have been used:

Tool	Description	Linux	Windows XP
SDCC	Small devices c compiler	2.8.0	2.7.0
gputils	GNU micor controler dev. package	0.13.4
KDevelope	Development environment		Not applicable
GNU Make	GNU Tools
Doxygen	Documentation Generator	1.4.6
fsusb	Bootloader	http://www.internetking.org/

Contact

The table below does summarize the contact points of the mkernel project.

Topic	Description	Responsible
Home Page	http://mkernel.sourceforge.net	michael.erdman@snafu.de
Technical Discussion

Accessing the Source Code

The source code is can be downloaded from the download area or accessed via the subversion archive.

This project's SourceForge.net Subversion repository can be checked out through SVN with the following instruction set:

svn co https://mkernel.svn.sourceforge.net/svnroot/mkernel mkernel

Or you may directly browse the repository.

Some Copyrigth notices

"The spirit of GNU" - Copyright (C) 1999,2000 Georg C. F. Greve Permission is granted to make and distribute verbatim copies of this transcript as long as the copyright and this permission notice appear.

“fsusb” - Copyright Author is Rick Luddy (GPG 1024D/98AA0510) <rickluddy@gmail.com>.

© 2007 Michael Erdmann - $Id$