Re: FW: [Gumstix-users] Robostix

[Dave H. <dhy...@gm...>]

Hi Sean,

I can answer some of the questions.

> Gordon, my experience in reading boards is too limited to understand
> the specifics of what's being described here, so I will just list what
> I'm *hoping* would be available on the board:
>=20
>         - at least two serial ports accessible directly from /dev/..., 3 =
would
> be better

The console /dev/ttyS0 and STUART /dev/ttyS2 are available in 5v
forms. There are also two serial ports from the ATMega128 which aren't
currently accessible using /dev/ entries, but they can be controlled
by the ATMega128.

>         - the serial ports are accessible via *TTL* with .1" pins, not so=
lder
> pads

Yep. each serial port has Rx, Tx, Gnd and V+ available in a 4 pin header.

>         - the console serial port is also accessible via RS232 (that'd su=
re be
> nice)

The console is accessible using TTL levels. So you'll need a voltage
converter like the one from Acroname or HVWTech.

>         - I2C available via .1" pins.  Pads in a a pinch.

There is a 4 pin header with the 5v version of the i2 bus (ATM_SDA,
ATM_SCL, GND, and V+)

>         - Board provides sufficient regulated power for analog in, digita=
l in,
>         and the board itself.  I think 500ma may not be sufficient.

There's 500ma for analog and 500 ma for digital I/O on the ATMega.
There's also 500 ma available for the gumstix. This assumes that
you're using a battery that can deliver that much. The standard
gumstix walwart can only deliver 1A total.

>         - Servo power can be jumpered to the input to the power regulator=
 so
> they're
>           off a common supply if that's useful.

Yep. If you look at this picture:
http://www.gumstix.org/schematics/B00019.top.png?nocache=3D1
there's a jumper in te bottom left called, BOARD, one called MOTOR and
one called JUMPER.

If JUMPER is left unpopulated, then the servo power needs to come from
the MOTOR connector. If JUMPER is installed, the servo power comes
from BOARD (same as the power jack).

>         - Provide whatever pads on the underside that you can provide fro=
m the
>           standard I/O expansion board.

There is one set of pads on the bottom of the board for PortA which
would otherwise be inaccessible.

> Some further questions: how difficult is it to program the atmel?  The
> big issue we'll have is writing and downloading (from the gumstix) two
> motor encoders onto the chip.  Otherwise we'll have to be polling
> digital ins from the gumstix, which no doubt would be a bad idea.

I use WinAVR, which is essentially the same GCC toolchain as is used
for the gumstix. You can find WinAVR over here:
http://winavr.sourceforge.net/

There's also a nice colletion of AVR routines for accessing various
hardware features over here:
http://hubbard.engr.scu.edu/embedded/avr/avrlib/

I highly recommend reading through the ATMega128 datasheet:
http://www.atmel.com/dyn/products/product_card.asp?part_id=3D2018

And there is an excellent web site with lots of resources for the AVR over =
here:
http://www.avrfreaks.com/

> Last, cost is a consideration.  What is your expected price range for
> this board?

I don't know the answer to this one.

--=20
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/