🚀 go-pugleaf

     If extreme accuracy isn't a major concern you may
want to consider using the game port on the Apple.  The
Apple II series and the Apple IIGS both use a 4 channel
A/D converter to read the voltage (via a variable resistor)
at the game port.

     You can read the value of the input voltage in basic with
the following command.

                    X = PDL(N)

N is from 0 to 3 and determines which channel is to be read.
X is the returned value (0 - 255).  The pinouts are as follows:

                    Apple II (16 pin socket)

     Pin #     Description         Pin #     Description
     1         +5 Volts            9         NC
     2         Switch 0            10        Paddle 1
     3         Switch 1            11        Paddle 3
     4         Switch 2            12        Annunciator 3
     5         Strobe Output       13        Annunciator 2
     6         Paddle 0            14        Annunciator 1
     7         Paddle 2            15        Annunciator 0
     8         Ground              16        Nc

                    Apple IIGS (DB9 connector - External
                             or 16 pin socket - Internal)
     Pin #     Description
     1         Switch 1
     2         +5 Volts
     3         Ground
     4         Paddle 2
     5         Paddle 0
     6         Switch 2
     7         Switch 0
     8         Paddle 1
     9         Paddle 3

     Note:     Max current from 5V supply <100ma.
               Switches are TTL inputs.
               Annunciators are TTL outputs.

As for measuring the fill factor I would recommend using a op-amp
as a current to voltage converter for the cell current and also
using and op-amp as a buffer for the cell voltage.  The gains
should be such that the max voltage is near 5V (the A/D reference
voltage).  Suitable scaling factors can then be calculated.  One
final note, although the returned value (0 - 255) would imply 8 bit
accuracy, I would expect accuracies of only a few percent.

						Bill O'Donnell
						(concerned citizen)