Re: [iPAQ] Help : accessing the extension port (FAST IO mode) of the ipaq

Valentin Longchamp wrote:

> Hello,
>
> I am working on a robotic project (http://team-id.epfl.ch) and we want
> to use an IPaq (precisely IPaq 3660) running Familiar (and OPIE) as the
> main controller of our robot.
>
> I am the main programmer of that part, and I want to use a linux process
> whose task would be to communicate with the sensors (make these info
> available for the other IA processes through a shared memory segment,
> which is well implemented in familiar) and send commands to the motors
> and servo-motors).
>
> According to that documentation
> (http://handhelds.org/Compaq/iPAQH3600/iPAQ_H3600.html), as we have many
> sensors and motors, we want to use the the Fast I/O mode of the
> extension port, because a 32 bits wide data bus is necessary, and a 10
> bits wide adress bus connected to our extern self-made address decoder
> (which is being developped by myself in the team too) would be widely
> enough for the number of sensors.

Are you sure you need all this bandwidth?

A simple solution with a ATmega16 (for instance) that comunicates using the
serial port is *much* easier to implement. The ATmega can be programmed in C
using gcc, and the software can be downloaded through a simple programmer
connected to a serial port.

You can get the serial port on the iPaq to go up to 230400 (I think, but should
be confirmed).

If you have a 50 Hz control loop (just throwing some numbers), at 230400 you can
get 460 bytes IN and 460 bytes OUT on each control cycle, through the serial port.

Unless you have image sensors involved here, I can't imagine why you'd need more
bandwidth.

On top of that, a microcontroller will already provide timers, PWM, A/D
converters, etc., that will release real-time demands from the host.

Of course I'm not saying that you don't need to use the bus (as I don't know the
project), I was just curious about the "why" you would need it :)

-- 
Paulo Marques
Software Development Department - Restinfor, Lda.
Phone: +351 252 290600, Fax: +351 252 290601
Web: www.grupopie.com
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