Atmel 8535 for engine management - Genesis

[Bernd Felsche]

Adrian Broughton writes:

>Hi Bernd,

>> I've started documenting the design ideas for an AVR-based ECU to
>> "replace" a Volkswagen Digifant unit. Tha aim is a unit which is not
>> only a plugin replacement, but also one which is expandable and can
>> take advantage of better sensor technology.

>I just read this post and was amazed, as I am using the same AVR 8535 unit 
>for a very similar data-logging/FCD/AFC/etc project I'm making for my 
>GT-Four.  As you can see, I also live in Perth.  You may remember I sent 
>you a private email a couple of weeks ago introducing myself.

Sure do.

>From the looks of it, my project isn't quite as extensive as yours (I'm not 
>looking at replacing the ECU, just logging sensor data and providing some 
>extra functions like controlling water injection, extra injectors, etc), 
>but there are many similarities.

I first intended to just design a data-logging unit to interpose at
the Digifant connector; but the hardware and a substantial part of
the software turns out to be identical for snooping and management.

The initial signal conditioning changes; the most significant
hardware change as Digifant drives the sensors - which are mostly
resistive, except for the pair of throttle position switches, Hall
sensor and the O2 sensor.  The hardware change from snooping to
management would require adding in suitable "drivers" for the
sensors and (of course) the outputs to coil and injectors.

The additional design and hardware overhead in separating out those
functions will help in debugging the unit. It also makes it simpler
to conceive - I like things as simple as possible. :-)

When I've sketched up the hardware block diagrams on a computer,
I'll put them on my web site.

My main concern at this stage is being able to fit all the software
into the relatively-small flash memory on the device.

>I would be most interested in sharing some ideas with you and maybe meeting 
>up in person at some stage (and possibly with Mike too).

I have no problem with that as long as it's no sooner than May.

Prior to that, I would like to establish my confidence in building a
uC-based device from scratch by implementing something really
simple; an interior light control for a car with door-ajar and
lights-on warnings. Goodies such as having the interior light come
on when you turn off the ignition and have the lights on, dimming to
off, interface to central locking, etc. will be thrown in, program
space permitting...

An 8535 would be an overkill. An ATtiny12 has (up to) 6 I/O digital
lines and on-chip oscilator in an 8-pin DIP.

>I work as a software developer and so the software side of things is my 
>real strength - and the hardware side is NOT.  I will be writing 
>data-logging software for PC, PalmPilot and probably WinCE OS's.  There are 
>a few other people helping out with my project, and we're hoping to 
>generate things like estimated real-time torque/hp curves.

Well, I have plenty of software experience (since 1977), mechanical
design, etc, but the hole I still need to fill is the detailed
design of the uC. Although I've tinkered with electronics for a
couple of decades, it's been analogue, discrete technology.

My ECU design incorporates a data bus onto which the main uC
"broadcasts" data frames of engine operations and various control
parameters. A "head unit" can be connected to this bus and placed in
the cockpit to display real-time information. The head unit can also
collect its own data from other sources (e.g. vehicle "speed"
sensor, GPS, etc) and combine them to give performance information.

A WOT-run in each gear through the rev range would be sufficient (in
terms of collected data) to program optimum shift points for
example.  A shift light display is simple enough to incorporate.

More details of that on my web page when I get around to putting
them there!

>Info on my project can be found at http://web.one.net.au/~gtfour/redbox/

Nice pages.

-- 
Real Name: Bernd Felsche
    Email: nospam.bernie at perth.DIALix.com.au
     http://www.perth.dialix.com.au/~bernie - Private HP
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