I have about decided to do a single chip solution to
   the dwell ignition problem because potentially it is the
   cheapest way to do a stand alone ignition for use with a carb.
   The knowledge gained can then be used to do a variety of simple
   things including a trim table adjustment to the 555 fuel injection
   system using spread sheet data as suggested by Henry Nee.

   I will focus on assembly language as these are time critical jobs
   and with assembly language you always know how long
   it takes to do anything. If you keep the job short and
   simple the software size will be manageable from many aspects.

   Further more I have considerable experience with assembly
   language much of which can be applied to the AVR instruction
   set.

   I realize that most of you will not be interested so you
   can delete the messages on the subject.

   Those that wish to follow along can make a folder and move
   the stuff over to that.

   Tom Walter, I think, was the first to mention the
   Arduino board as a good low cost and small AVR trainer that will
   do a variety of jobs. The advantage is it is wired
   for USB and there is programming software that runs
   on both Windows and Linux.

   There are a lot of people using this board around the world so there
   should eventually be a lot of asm code examples.

   The Arduino Mega 2560 is a small microcontroller board based on
   the ATmega2560. It has 54 digital input/output pins (of which 14
   can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware
   serial ports), a 16 MHz crystal oscillator, a USB connection, a
   power jack, an ICSP header, and a reset button. It contains
   everything needed to support the microcontroller; simply connect
   it to a computer with a USB cable.

   We will be using only a very few of these capabilities but the
   cost and size is so low it does not matter.

   AVRA is an assembler for Atmel AVR microcontrollers, and it is almost
   compatible with Atmel's own assembler AVRASM32.

   The initial version of AVRA was written by John Anders Haugum in
   1999. He released all versions until v0.7. All later versions were
   released by Tobias Weber. And version 1.3.0 is released by Jerry
   Jacobs.

   Paul Lamar

   Runs on a Mac too. This is the board we are using in the
   Mechatronics
   courses at the University of Utah. Mostly for automated robots
   with lots of sensors.

   Chris Cosman

   Paul,

   The AT90USB Demo-Kit sells for 31.00 on Digikey and I think
   provides similar resources, plus has some external flash storage
   that might help for storing tables. Check it out, as it could be a
   cheaper alternative.

   Thanks,
   Brannon

   That is a bargain. I had to call and confirm it was completely
   assembled.
   That beats the Arduino for our purposes. Thanks for finding that
   Brannon.
   I ordered one.

   Paul Lamar

   Paul,

   No problem, happy to help. Let me know if you would like any help
   coding
   this up or if you'd like someone to review your code. I've done several
   designs on these processors and one on this board in particular.

   One note, you might want to consider writing the majority in C, as
   you will be able to use the Atmel supplied libraries for USB
   communication, etc, and coding your time critical procedures in
   assembly. Most compilers have statements that allow you to write in-
   line assembly. Also, you can always generate the .lst file on
   compile and see what assembly is being generated for any code you do
   write in C.

   Thanks,
   Brannon

   Great Brannon!

   Good to hear it. Here is the problem.
   At 7500 RPM the engine makes one rev in 8 ms.

   The RX8 coil delays a fixed 2 ms after the crank sensor tells
   it to fire. This is called dwell. In effect what this does is retard
   or reduce the advance near 90 degrees. That causes the spark to fire
   about 70 degrees AFTDC!!!!!! Of course losing power in the bargain
   and hurting the BSFC. (fuel burn).

   My suggestion is to measure the period of a given RPM and anticipate
   the advance required up to 2 ms at 7500 RPM for the next revolution.
   As you go through the rev range of course the adjustment changes. No
   adjustment at idle and a lot
   (2ms) at 7500 RPM.

   Any ideas? Do you have a scope you can test it with?

   CD's don't do this but they are a lot of bucks compared
   to the LS1 or RX8 coils with built in solid state switches.

   Paul Lamar


   Automotive computer ignitions use the previous CAS signal to fire the
   plug
   you want. It is easy to delay the firing event, but anticipate it?
   What could
   be used is the adjustable pick-up mounting and a timing light to find
   where it
   needs the pick-ups to be to get the advance required. Once the
   position is
   determined for the set-up, the rest should be close with a small
   adjustment
   like setting timing on the distributor.

   Dale Davies

   Well if you measure the time it took to rev the engine once
   and subtracted 2 ms when you fired on the next rev I think that would
   work.


   Paul Lamar


   For a 2-rotor, measure the time for half a rev by timing from rotor1 CAS
   to rotor 2 CAS, then subtract the 2 ms.

   For CDI you can get motor scooter ignition packs for under $10. Use two
   in parallel and deliver 40 millijoules to the coil. 4 wires to each pack
   - 12 volts, ground, output to coil, and trigger. They are made to work
   with inductive CAS sensors.


http://www.scooterpartssale.com/index.php?main_page=product_info&cPath=71_77&products_id=191



   Victor Roberts

   That might work for a 2 rotor. Our immediate need is for a one rotor.

   Paul Lamar

  Why not set the physical timing so that the plug fires at the desired
  advance by default at 7500 RPM and then use the software to delay the
  firing at lesser RPMs.  Anticipating the event is a bit harder to code
  than reacting to the event after it occurs.  The computer will be
  calculating a timing retardation instead of a timing advance.

   Mark LaPierre

  I got the $30 AVR Explaine test board. Lots of I/O to test a program.
  Switches for inputs. LED and a speaker for out put.
  Probably more powerful than an IBM mainframe from just a few
  years ago.

  Paul Lamar


Just wanna verify the unit shown above is: ATAVRXPLAIN-ND "KIT EVAL FOR
ATXMEGA128A1" as listed in digikey catalog.

Ed Carver

Correct Ed. There is a lot of free doc from various web sites.
There are at least two free assemblers.

Also there are one or two IDE Integrated Development Environment's that
you will need. It is a software program that talks to the board and sends
it assembled program through the USB. The USB also powers the board.
I am not sure but sometimes the assembler program
has a built in IDE.

It was so cheap I had to call DigiKey and confirm it was completely assembled
and functional out of the box.

------------------------------------------------

This site will be a big help in getting you started Ed.

http://avrbeginners.net/

This is an extremely well done site maintained by AVR.

Here is a way to cheat and speed up the process of learning.

Cheat! Get somebodies else source code and fool around with it :)
Back when I was learning I did not have that option. No Internet.


Paul Lamar