Very Computer

I'm new to microcontrollers.  What i would be using the microcontroller
for it autonomous sumo robotic wars.  The microcontroller would have to
be able to power a circuit that could power D.C. motors at high
current.  What would be the best microcontroller?  Also which
microcontroller is better for expansion?

First there is cost. The Handyboard is significantly more expensive than
the BasicX.  The BX-24 chip is $39.95, and is a self-contained
circuit/microcontroller. You can just plug it into a 24-pin socket, apply
juice, and you're off. The Handyboard is really a full single-board
computer, with all the complexities that entails.

Second is programming. The BX-24 is probably easier to program if you're
just starting out, as it uses a variant of Visual Basic. The Handyboard can
be programmed in a variety of languages, with Assembler and C the most
common.

As far as raw power is concerned, the Handyboard wins hands down. Learning
how to use that power doesn't necessarily come easy.

Expansion is in the eye of the beholder. What kind of expansion did you
have in mind?

Few microcontrollers by themselves have built-in high-current ports. Rather
you can attach to them a wide variety of transistor, power MOSFET, or
H-bridge drivers, relays, etc. to do this work for you.

-- Gordon

Quote:> I'm new to microcontrollers.  What i would be using the
microcontroller
> for it autonomous sumo robotic wars.  The microcontroller would have
to
> be able to power a circuit that could power D.C. motors at high
> current.  What would be the best microcontroller?  Also which
> microcontroller is better for expansion?

Be sure to look at the OOPic
http://www.oopic.com

Also look at the robots on the OOPic website
http://www.oopic.com/robots.htm

--
SMS

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= OOPic robots http://www.oopic.com/robots.htm =
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Before you buy.

What raw power?  The Handyboard has more I/O than the BX-24,
is it faster if programmed in IC?

John-

Things like direct access to hardware timer inputs (the BX-24 lacks this),
ability to expand RAM (can't do it with the BX-24, but you can with the BX-01),
and of course the ability to use the native assembly language calls of the
controller, such as whatever the equivalent is for "skip on bit set/reset" for
the HC11.

Remember that a BX-24 stores user programs in EEPROM.  The HC11, or most any MCU
not driven by an embedded language, will store programs either in burned PROM,
Flash or downloaded SRAM.  Because these allow faster fetching of instructions,
speed is improved.  I recall the BX-24 processes about 8,000 instructions per
second. The Atmel 8535 chip upon which the BX-24 is based processes up to
8,000,000 instructions per second. The HC11 may or may not be as fast, depending
on the crystal used. When you program in IC, IC converts to ASM. For the BX-24,
your program is stored as tokens, which are intepreted by the BasicX operating
system that permanently resides in the BX-24's Flash memory.

This isn't to say that the BX-24 is not a good alternative, because it is. But
in my opinion there 's a compromise of power/speed for conveience.

-- Gordon

I should add that the BX-24, like many embedded-high level language controllers, use
*serial* EEPROMs for user program storage (serial is used as opposed to parallel so
save on I/O pin usage). The internal EEPROMs of the microcontroller doesn't have
enough storage space to provide for user programs of any meaningful size.  So,
instead of fetching an instruction on a byte-wide program bus, the BX-24 has to
fetch it one bit at a time. Again, this is typical of these kinds of controllers.

-- Gordon

<snip>

Quote:>    [...]
> Remember that a BX-24 stores user programs in EEPROM. The HC11, or
> most any MCU not driven by an embedded language, will store programs
> either in burned PROM, Flash or downloaded SRAM. Because these allow
> faster fetching of instructions, speed is improved.  I recall the
> BX-24 processes about 8,000 instructions per second.

Well, this depends greatly on the instruction. An empty for-loop with a
16-bit counter is slightly faster. Floating point multiply is slightly
slower, as is procedure call/return. Other instructions, such as
integer increment, can run at 65,000 per second or higher.

Quote:> The Atmel 8535 chip upon which the BX-24 is based processes up to
> 8,000,000 instructions per second. The HC11 may or may not be as
> fast, depending on the crystal used. When you program in IC, IC
> converts to ASM. For the BX-24, your program is stored as tokens,
> which are intepreted by the BasicX operating system that permanently
> resides in the BX-24's Flash memory.   [...]

It depends on what you define as a token. BasicX uses an optimizing
compiler that compiles to a virtual machine similar to p-code or Java
bytecode. We don't use the traditional BASIC approach of tokenizing
source code that is interpreted on the fly.

One advantage to this approach is that b-code tends to be significantly
more compact than equivalent native code, which can be an advantage for
small memory systems.

-- Frank Manning
-- NetMedia, Inc.

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Before you buy.

Actually, I realize now I was remembering the "8000+" instructions for
program storage space. They're right next to one another on the BX-XX
comparison lists, and my "photographic memory" misplaced the two!
Still, though, 65K/second instructions is not close to the 1-2 cycles
per instruction that an 8 MHz Atmel chip is capable of, and that was my
point. In order to enjoy the benefit of a high-level language embedded
into an MCU, there's usually a trade-off, and in this case it's raw
processing speed. I think these kinds of tradeoffs are to be expected.

Quote:> It depends on what you define as a token. BasicX uses an optimizing
> compiler that compiles to a virtual machine similar to p-code or Java
> bytecode. We don't use the traditional BASIC approach of tokenizing
> source code that is interpreted on the fly.

I didn't want to use the term "bytecode" because that has taken on a
special meaning these days (because of Java mostly). I guess "token" is
a loaded word, too.

-- Gordon

Thank you Gordon, and Frank, for the clarifications.

John Piccirillo