Re: companies selling reliable microcontrollers and sensors....
- From: "Randy M. Dumse" <rmd@xxxxxxxxxxxxx>
- Date: Mon, 15 May 2006 22:18:37 -0500
"Mark Smith" <mophobia@xxxxxxxxx> wrote in message
news:1147658351.928643.63410@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Other than Parallax...do you recommend other companies? Also,
any feeling on using Parallax as a starting point?
Let me answer the sensor question first. I like two companies that sell
sensors. One is www.junun.org, which is very reasonably priced. The
second is www.Acroname.com for a wide range of sensors. I'm sure there
are other resellers of sensors, but these are my personal first choices.
Now. Comparing processors and the companies that make them is and always
will be somewhat of a religious issue. Different people prefer different
models, just as there are loyal Ford, GM, and Chrysler owners, then a
few, who select particular cars for features per price, rather than by
manufacturer. Different strokes for different folks.
Still, since you asked, I feel I can respond. Please note my commercial
bias and understand I have a vested interests in what I say. Don't think
that doesn't mean I am not 100% sincere about what I say, though. For
reference, I am also a Senior Adjunct Instructor teaching robotics at a
university at the upper undergraduate/graduate level.
My company www.newmicros.com sells very reliable microcontrollers, and
we've been doing it about 10 year before Parallax got started at it. Our
current 'Pod controllers about 10 years newer, more-modern design than
the Basic Stamp, are excellent for motion control, and particularly
robotics. I think they are muh a better choice, and I doubt you will
outgrow them anytime soon.
There are many other owners of companies which supply boards which post
here, who also make excellent boards, which I think would be better to
start with than Basic Stamps. Dan Michaels www.oricomtech.com for PICs
and Brian Dean www.bdmicro.com for AVRs come to mind.
Since you ask about using Parallax as a starting point, in my opinion,
if you are a beginner and want to progress to the end goal of being an
advanced beginner, it will do. If you want to really progress beyond
being a beginner, you will need (sooner or later) to leave Basic and
stamps behind. So to me, the issue is how much do you learn using Basic
and stamps, vs., how much do you learn to do wrong. To wit:
The Parallax Basic Stamp can only do one thing at a time. As a result,
you can easily learn how to write a program to control one thing at a
time. (No robot of significant utility can be programmed that way.) You
also learn some very bad design habits when you try to control more than
one thing at a time, in my opinion.
For instance, you can control one RC Servo by using pulse generation
command, PULSOUT. But for the milliseconds the processor is doing this,
you can not do anything else. Then for another 18 to 19 milliseconds,
you should not output a pulse.While the processor is doing this, you can
not do anything else. If you use the PAUSE command to get this quiet
time right, all your processing power is consumed driving that one
Servo. You can't control another thing, not even a second RC Servo on
your robot's other wheel.
Consequently, for a two wheeled robot, you will usually have to cheat on
the timing. You do two PULSOUT commands in a row, then hope other
processing is done roughly at 16 milliseconds. You hope you get close
enough to fool the Servos into seeing it as a valid refresh cycle. Or
you can't drive your robot reliably. And you can forget about reading a
serial channel with a long string, or timing something else like the
echo from sonar ranger. etc.
See their own forums to verify this is the case:
http://forums.parallax.com/forums/default.aspx?m=125500&f=5&p=1
So what do you learn to do here using a stamp? Well, most folks quickly
learn it is easy to program a stamp to do one thing. They then learn its
hard to do useful programming with three or four things going on at
once, and never get much further. Or they conclude they need more micros
to get several things done. Some folks buy a Serial Servo Controller
(about the price of another Basic Stamp) to be able to off load the RC
Servos from the stamp. Later they start splitting up the tasks using
more and more controllers either stamps, or by then, PIC's or AVR's
programmed in some other language, each doing one thing at a time (plus
a second task of talking to a central controller telling them what to do
which is hard to do while controlling the one thing).
But virtually no one learns the "right" way, the way serious roboticists
and programming professionals do multitasking on several complex
problems at once, from a Basic Stamp.
I started learning BASIC as about my fifth language, in the early '70's,
well before it came to microcomputers. I liked it so much (not), I soon
switched to assembler for micros. Since 1980, when I went to work for
Rockwell as a professional, I've seldom touched Basic for my own use.
Also, from my experience as a supplier of Basic as well as other
languages on some of our past products, I've found the programmers using
Basic are often the most lost, and need the most help completing their
projects.
Likewise, others have noted problems. For example, most non-beginers are
aware of things like this, taken from Wikipedia BASIC article: "In a
1968 article, Dutch computer scientist Edsger Dijkstra considered
programming languages using GOTO statements for program structuring
purposes harmful for the productivity of the programmer as well as the
quality of the resulting code..."
I think you'll find plenty of amatuers that will vouch for Basic. Many
professionals got their start, or had early experience as did I, with
Basic. But I doubt you can find many serious professionals who would
recommend it today, beyond as a beginner's first stepping stone. I can't
even do that, because I think you learn bad habits which are hard to
unlearn later.
--
Randy M. Dumse
www.newmicros.com
Caution: Objects in mirror are more confused than they appear.
.
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