Matt,
I set mine up for analog on pin 1.
I used a pot off the 3.3 v supply
Here is the results.

There is quite a bit of variation in the hundreds of volts.
  (.01) I need to look at the 3.3 volt supply with my scope to see
if there is any noise on it.

It also takes about 6 msec for the A to D and the print on the screen.

I'll remove some of the characters sent to the screen and see if that helps.
I suppose saving the data on the SD card would take longer than writing
to the screen. We shall see.

Mode 1


SetPin 1, 1 'set pin 1 to analog in
Timer = 0
For x = 1 To 35
data1=Pin(1)
Print data1;
Print "   ";
Print "  Number of msec =";
Print Timer
Next x

-------------------------------------------------------------------
As I suspected it took a lot of time to display all those characters.
As a matter fact for an EFIS you want to set a 1 second hardware interrupt and update
the screen every second. If it has a noticeable blink set the up date
interrupt to a half second update. Then the time to send characters to the screen
is minimized.

I was curious about how long an actual  A to D conversion took so I wrote this program
and connected by scope to pin 19.


Mode 1

SetPin 19, 8 'setpin 19 to output
SetPin 1, 1 'set pin 1 to analog in
start:
Pin(19) = 1 'put pin 19 high
data1=Pin(1) 'actual A to D conversion
Pin(19) = 0 'put pin 19 low
GoTo start

For the actual A to D it took about 450 usec. Then to go back and set the pin hi again
it took about 50 usec. This is a BASIC interpreter a BASIC complier for the Maximite would
be nice. Setting a pin hi and low in a Coridium ARM BASIC compiler happens
in one or two microseconds.

The idea for sampling the manifold pressure at the oil injector hole should be done
just after the apex seal closes off the p-port. This happens about 90 to 110 degrees
after top dead centre. Since the second gen crank angle sensor has two triggers
one about 20 degrees BTDC for the ignition and a second trigger every 30 degrees.
(24 teeth running at half e-shaft revolutions.)

This allows you to sample the manifold pressure at the same place in the intake cycle
every time. That should result in a much more consistent mixture setting.

Tracy never told me when he sampled the MP. I suspect it was at random. In addition
it varied with the turbulence in the intake manifold so everybody had a lot
of trouble tuning Tracy's EFI system. No two system sampled the manifold
pressure in the same place. The Mustang 2 p-port had the oil injector hole pressure
tap which yielded more consistent data. If sampled at random you had to use
a container to average out the pressure variations. That was a less accurate way
of doing it.


Paul Lamar

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