Date:         Thu, 14 Nov 2013 07:29:29 -0800
Reply-To:     Brett Ne <brettn777@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Brett Ne <brettn777@GMAIL.COM>
Subject:      Re: Arduino and Vanagons
In-Reply-To:  <52845EAC.3030408@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

Alright, it looks like there is enough interest and knowledge base to
proceed with this project!  Let's get started...

James, thanks for the info, it is very helpful.  I too have worked with PIC
microcontrollers for many years and am quite content to use either
Atmel(Arduino) or PIC microcontrollers.  Really, any microcontroller with 4
digital inputs, 2 analog inputs, and 1 PWM output should work just fine.  I
would tend to lean towards the Atmel for the following reasons:
    *The Arduino programming software is freely available for Windows,
Linux, and OS X
    *The Arduino platform has incredible user support worldwide for both
beginners and advanced users
    *The Arduino programming software is a decent compromise between power
and ease of use
It sounds like there are several members that have little or no experience
with microcontrollers/programming but are curious about how to use them in
projects such as this, and we can facilitate that by selecting a
platform(combination of hardware/software) that is beginner friendly.  That
being said, I can certainly be talked into using PICs or another brand.


David Beierl sent me a picture of an oscilloscope tracing from the coil
primary circuit during firing and boy, is it ever anti-friendly to
microcontrollers!  There's a decent spike up around 30 volts and a very
brief spike of over 200 volts!  Fortunately, we don't have to worry about
that.  Initially I assumed that since the tachometer in the instrument
cluster is driven by the coil primary signal, that the tach info to the ICU
would have the same source, but it turns out that it gets tach info from a
common connection (with the ECU) to the output of the Hall sensor.  The
Hall sensor won't be above 12 volts(keep in mind that in a car, 12V could
really be anywhere between 9-16V).

So, I've spent some time looking through Bentley and looking at some other
sources online to sort through the various connections to the ICU.  Below
is a listing of what I've found.  Please look through for any mistakes or
misunderstandings.  The terminal numberings are those used in the Bentley
wiring diagram for the Digifant 1986 system.

ICU(Idle Control Unit) connections:
6/50  Digital input from the starter switch
        high when starter is engaged
        low when the starter is not engaged

14/15  12V power supply to the ICU whenever the ECU has power
           Also supplies power to the power steering pressure switch

15/LH  Digital input from the power steering pressure switch
           high when power steering is engaged
           low when power steering is not engaged

5/31  Ground connection to the ICU

13/T  Analog input from the coolant temperature sensor

8/LS  Digital input from the throttle valve switch
         high when throttle valve closed or wide open (I'm guessing here)
         low when thtrottle valve partially open (I'm guessing here)

4/ST2  PWM output to the idle speed stabilizer valve    Note: One of ST1
and ST2 is an ground connection and the other will be a

PWM power source. Must be tested to see which is ground.
11/ST1  PWM output to the idle speed stabilizer valve

2/K  Digital input from AC compressor
       high when AC compressor is on
       low when AC compressor is off

17/1  Analog input from the Hall sensor   What is the typical for the
baseline voltage and the peak voltage?


That's what I've gathered so far.  Please make corrections/clarifications.



Brett