Title:  Patterns to Ease the Port of Micro-kernels in Embedded Systems

Author: Michel de Champlain         
Email:  michel@cosc.canterbury.ac.nz

Department of Computer Science
University of Canterbury                    
Private Bag 4800                           
Christchurch, New Zealand                   

Phone: +64 3 364-2362 Ext.7727  

Abstract:

Micro-kernels are difficult to port to a new hardware platform. 
During the initial phases of a port, much time and effort is lost on 
debugging critical machine-dependent subsystems. These subsystems 
are generally very tightly coupled and cannot be tested in an
incremental fashion. Tight coupling occurs because the subsystems
share many global variables forcing them to be debugged with the 
complete micro-kernel's code. The problem of porting and testing 
new micro-kernel ports has so far received little attention,
and the work described in this paper is an attempt to fill this gap.

A design pattern captures and communicates the development and reuse
of frameworks in a specific context.A framework consists of several 
software components and their interaction. In the embedded domain, 
we have found design patterns very useful to encapsulate requests, 
to decouple subsystems, and to make policies interchangeable.

We describe the design and implementation of various object-based
design patterns which address the problem of the initial porting of 
micro-kernels for embedded systems in a systematic and incremental 
fashion using bottom-up integration testing. The rationale behind
major design decisions is presented along with an outline of the 
general framework of patterns. We also present the forces and 
applicability of our design patterns for each phase of the port. 
In the course of several iterations, these patterns have been tested 
and refined through their use in porting of an existing 
embedded micro-kernel to different hardware platforms.