Paul,

  I do have a scope and I have one of these boards already, so I can
  probably code something up for you pretty quickly.

  I'm much better on the microcontroller side than the engine side, so I'm
  going to break down the problem into what the micro would actually have to
  do and you can clarify for me so I can put some code together.

  So, there is an input digital waveform that we need to read the period of.
  From the period we can calculate RPM.  Based on this RPM, we can determine
  an advance (0 - 2ms).  This advance is then somehow output to the overall
  coil timing of the system.

  A few questions:
  1) What is the required RPM resolution?
  2) How is the output advance fed to the rest of the system?  Does the
  microcontroller output the advance or the overall waveform for the coils?
  3) Do you have example input and output waveforms?

  Sorry if these questions seem a bit naive in light of the overall issue,
  but I've been following this list for a short amount of time and am still
  very much learning the fundamentals of rotary operation.

  Thanks,
  Brannon



  On Nov 22, 2011, at 18:21 , Rotary Engine wrote:


   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 give 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


 What kind of help would you like on this project?  I think you ordered a
 different board, and it sounds like you are already coding things up.

 Let me know.

 Thanks,
 Brannon

 It had a lot of I/O on it in the form of input switches and ouput LED's
 and it was so cheap ($30) I could not resist. Just blink an LED when a
 switch
 is pushed and we will use that as a simple starting program.
 I'll explain it step by step for instruction and discussion.


 Paul Lamar


Paul,

Here's a simple routine that flashes an LED at Port B1.  If you send me the
output port that is going to the on-board LED, I can modify the code
appropriately.  The LED flash frequency is also dependent on the micro
clock frequency, and can be modified by adjusting the quantity
LED_FLASHCOUNT found in LED.h.  I compiled it in AVR Studio 4 and had no
issues.

This is in C, and is well commented...let me know if this is the type of
example you are looking for and I will expand it to flash the LED when a
button is pushed.  Currently, it shows how to configure an output, and how
to use an on-board timer to generate precise timing.  For the real app, I
would probably use an interrupt, but as a first example that would probably
get a little complicated.

Thanks,
Brannon

Can you do that in asm? Down the road when we get to time critical
application we will need to do it in asm.

Paul