Re: microcontrollers under $50?

In article <4653A926.1020105@xxxxxxxxxxx>,
"Wayne C. Gramlich" <Gramlich@xxxxxxxxxxx> wrote:

But a bigger problem for me is all the support stuff these chips seem to
require -- capacitors, resistors, etc. An internal oscillator does
reduce the part count somewhat, but not to zero, right? How's a poor
software guy like me supposed to know what these parts are and where
they go?

Well, actually, there are no other parts, just supply 5 volts.

Really? I didn't know that. But in a board like this:

http://www.futurlec.com/ATMEGA_Controller.shtml

....all those extra parts really aren't adding any value beyond breaking
the surface-mount chip out to header pins? I see a voltage regulator,
and you did mention that; but I also see about a dozen capacitors, five
or so resistors, another IC, and a little oval-shaped thingy that I
don't know what it is (the crystal maybe?). One of the resistors is
serving the on-board power light, and so counts as part of the power
supply. But what's the rest of that stuff for?

The biggest problem with microcontrollers is their initialization,
but once you have one example of a program that works, it
can usually be modified forward to keep it working and doing
useful things for you. Getting that first program working
can be a real bear tho'.

Too true.

Actually, a well designed board does not really help
get the first program working.

Well, it does help with all that other stuff which you say isn't needed
but which I can't help feeling must be doing some good, since all the
controller boards have them. :)

What helps is that the board comes with a demo program that
somebody else has already figured out.

That depends on the board. With the ARMexpress, the compiler is
onboard. The complete steps to get going are pretty much

1. Connect a serial cable to the ARMexpress serial input
2. Fire up a terminal program and connect to that port
3. Type
PRINT "Hello world!"
RUN

Getting started with the AVR Butterfly, for example, is a LOT more
involved despite the serial bootloader. (Or so I gather, though I
couldn't find anyone or anywhere that could actually explain how to do
it.)

The real problem you are facing is a documentation problem.
There is tons of stuff out there that makes a fine and
dandy robot controller for a low end robot, but the amount
of stuff out there with adequate documentation is much harder
to come by. The spec. sheets for PIC's and AVR's are complete
but hardly easy reading.

Yes, that's true. There's also a difference in convenience. You said
yourself (IIRC) that you like to put your PIC or AVR on a carrier board
that gives you buttons, lights, and other conveniences (which I would
guess includes header pins, mounting holes, a power supply, etc.).

I think this depends partly on what you're doing -- if you're working on
a prototyping breadboard, or designing your own PCB, then a bare chip
(or a DIP board, like the Stamp form factor) is quite convenient, and a
big board with header pins is actually more of a PITA. But if you're
trying to avoid extensive breadboarding and just bolt a reliable
controller onto a bot, then a bare chip or Stamp board is a PITA and a
board with headers is more convenient.

What got me excited this week about the Futurlec mini-boards is that
they've picked a couple of standard connectors, and made a lot of small
boards that (it appears) you could just cable together to make a wide
variety of complete packages. Start with a controller, add a switching
regulator if it lacks one, throw in a sound (or even MP3) board, an SD
card reader, a motor driver or two, and pretty soon you have a bot.

But in the meantime, I find myself doing a lot of breadboarding, and
preferring the Stamp form factor. I'd be happy with a chip too if I
could just connect a serial cable and talk to the dang thing from my
Mac. It sounds like with the right tools, I can almost do that with the
Atmel chips, but as you say the docs are lacking.

Hmph. Maybe I'll buckle down and figure out the AVR toolchain. But
next month -- this month, I have a bot to build...

Thanks,
- Joe
.