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From: mfb@mbunix.mitre.org (Michael F Brenner)
Subject: Re: ada and robots
Date: 1997/05/29
Message-ID: <5mjqpq$lkp@top.mitre.org>#1/1
X-Deja-AN: 244706109
References: <338CDA96.53EA@halcyon.com>
Summary: Ada has the required features for microcontrollers
Organization: The MITRE Corporation, Bedford Mass.
Newsgroups: comp.robotics.misc,comp.lang.ada
Date: 1997-05-29T00:00:00+00:00
List-Id: <comp.lang.ada>


The Ada language has the required features for programming controllers:
low level bit operations, absolute memory addressing, interface to 
assembler code, interrupt handling, etc. It also has a number of features
not required, but helpful for programming controllers: the best bug
catching at compile time, some of the best encapsulation, the ability
to express many algorithms without bug-prone pointers, good optimization,
ability to do tasking, etc. In a toy robot, the controllers do not need
much programming, usually an external scheduling computer does the
dynamics and kinematics, resulting in a set of curves that the controller
follows, programmed in an ASIC or a PROM as numbers with a very tiny
program to put those numbers into a memory mapped board register, and
the hardware does the rest. In autonomous robots, however, where each
tick of the clock requires computation a Kaman array of Kalman filters,
adjustment of the boundaries in a Voronoi diagram, and reclustering
of the distance and force matrix between obstacles, the controller
of a joint looks a lot more like a complex general-purpose computer
with specially designed I/O circuits. In the first case, the toy
robot, it does not matter which language you use because there are
so few actual instructions required, if the whole thing is table-driven,
or else the instructions are boiler-plate macros stamped out by some
finite state machines, where, again, source language is irrelevant,
they are just a bunch of gotos mixed with set-port commands at the machine
code level. In the second case, the sophisticated bug control and
packaging features of Ada can help develop the code faster than other
languages, regardless of whether Ada is the target language; that is, 
after developing in Ada, if you find that the code is mostly just a
bunch of FSAs anyway, you can stamp them out as boiler plate assembler code,
using those same FSAs with a different action matrix, and use that
assembler code as the target. However, in an autonomous robot, Ada might
be the best language for the final target as well.