Re: [CAD_CAM_EDM_DRO] EMC? Jon ?

On 23 Jul 2005, at 23:14, Roy J. Tellason wrote:

> (Never saw a Jupiter ACE, though. :-)

They're pretty rare now; probably worth a few bob.

> So I looked into it, and while there's a fair amount of programming
> capability in there, it was real difficult for me to see how this
> could be
> used in any sort of a control application. Maybe that was particular
> extensions that were written for it or something? In any case,
> I'd like to
> implement some stuff using it, but need to find more info, if any
> of you
> guys know of any.

Forth's popularity is waning now (the UK Forth Interest Group
recently announced they will no longer be publishing a journal), but
there are still plenty of die-hards around who claim that Forth lets
them be several times as productive as C programmers. Forth has some
unusual features which make it well suited for low level control type
applications. The language, the development environment, and the OS
(typically with multitasking ability) are all part and parcel of a
traditional embedded Forth system. Despite this, the systems are
usually very small (much smaller than a comparable C based OS and
toolchain). Forth systems are traditionally interactive- you connect
a terminal up to them, write snippets of code, and immediately try
them out. The language is very extensible- in effect you write a
Forth program by inventing your own words (describing them using
sentences of simpler built-in words or words that you have already
invented yourself) and then eventually making a top-level sentence
out of your invented words. This interactivity and extensibility
encourages bottom-up development, which is great when the main
purpose of the program is to interface to hardware, as in most
embedded control systems. Forth is also usually pretty fast - not as
fast as C, but much faster than a BASIC interpreter, and the code it
produces is generally very compact indeed - much more compact than
compiled C code (part of this is due to the development philosophy
which encourages the use of lots of very short reusable words).

The way I see it, Forth is a useful tool for low level stuff (eg.
interactively debugging a new piece of hardware), but it can be
difficult to understand other people's Forth code (especially if they
haven't bothered with comments), and high level stuff can get ugly,
especially all the manual data stack manipulation.

There are also a couple of companies which sell expensive
professional Forth development systems for embedded systems which
include a flashy GUI and optimising compilers that produce code about
as fast as compiled C code. They're intended to compete directly with
the high-end C development systems.
http://www.forth.com/
http://www.mpeltd.demon.co.uk/

> I think an outboard box with 8-bit parts running Forth might make
> one heck of
> a nifty addition to a CAM setup... :-D

There's lots of ready-built Forth hardware around, including more
powerful stuff like tiny LPC2106 (60Mhz 32 bit ARM with 64K of RAM
and 128K of Flash) based boards:
http://www.mpeltd.demon.co.uk/tiniarm.htm

--
------------ Alex Holden - http://www.alexholden.net/ ------------
If it doesn't work, you're not hitting it with a big enough hammer