FYI: Paul Stoffregen is working on full Arduino Mega support for
Firmata/Pduino. I know some people onthis list were interested in
that. He's looking for testers now, the code is here:
http://www.pjrc.com/tmp/firmata/
Once its tested, we'll work on integrating it into the regular Firmata
releases.
.hc
Begin forwarded message:
From: Paul Stoffregen <p...@pjrc.com>
Date: January 5, 2010 10:12:55 AM EST
To: firmata-de...@lists.sourceforge.net, Hans-Christoph Steiner <h...@at.or.at
>
Subject: better hardware abstraction
User-Agent: Thunderbird 2.0.0.23 (X11/20090817)
I just uploaded a copy of StandardFirmata using what I believe will
be much better hardware abstraction.
http://www.pjrc.com/tmp/firmata/
The concept is use two sets of macros, IS_PIN_xxx() to test if any
particular pin supports a feature, and PIN_TO_xxx() to translate
firmata pin numbers (as used in the protocol) to actual numbers used
by the hardware functions.
Often these macros are very simple. But when a translation is
needed, they can. For example, on a standard Arduino, for digital
pins the macros are:
#define IS_PIN_DIGITAL(p) (((p) >= 2 && (p) <= 13) || ((p) >=
16 && (p) <= 21))
#define PIN_TO_DIGITAL(p) (((p) < 16) ? (p) : (p) - 2)
Pins 14 and 15 are not implemented, and pins 0 and 1 are not
available for digital I/O due to being used for Rx and Tx. The
PIN_PIN_DIGITAL() macro lets StandardFirmata easily adapt. The
PIN_TO_DIGITAL() macro is used whenever calling pinMode,
digitalWrite, digitalRead (but optimized 8 bit port access has to be
special coded). For a standard Arduino, when the analog pins are
used as digital I/O, this macro makes sure pinMode gets called
correctly. Even though it's pin 16 as presented by Firmata,
Arduino's pinMode function expected 14 to map to the first analog
input.
The core concept behind this abstraction layer is every "firmata
pin" may support any number of features which are checked with
IS_PIN_xxx(), and if the feature is available, PIN_TO_xxx()
translates the "firmata pin" into a "hardware pin". Everything in
StandardFirmata works based on "firmata pins" and then checks and
translation into "hardware pins" are used when actually performing I/
O.
This simplifies the StandardFirmata code in many places. In the
long run, I believe this approach will be much more maintainable,
since it tends to make the code more readable. As more pin features
are added, this scheme is simple to extend.
As promised, I've done quite a bit more testing. I modified Pduino
to work with more pins and did quite a lot of testing on Arduino
Mega (on 0017, there is a known bug with analog inputs 8 to 15, so
be sure to patch your wiring_analog.c file, if you haven't
already). I haven't tested everything in every possible way, but
this does seem to be working quite well.
I realize this is a pretty substantial change. I hope you'll
consider it.
-Paul
----------------------------------------------------------------------------
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direct solution... It may sound small in theory, but it in practice,
it can change entire economies. - Amy Smith
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