Wiardgroup

Hi Woody
   --- In wiardgroup@yahoogroups.com, "woodyy_wall" <woody_wall@h...> wrote:
> I am wondering is can anyone explain
> the relationship between the "Ring" lights and the bits flowing
> through the shift register. It seems that higher voltages are present
> when the LEDs are red, but I can't quite understand how the three
> states (green, red, off) relate to the two states (one, zero) of the
> shift register. 

the shift register is an 8-bit register divided into two four-bit 'nibbles'.
the first nibble is:
do
d1
d2
d3
and the second is 
d4
d5
d6
d7

the  4 leds indicate a comparison between the states of the following pairs of bits:
d0 - d4
d1 - d5
d2 - d6
d3 - d7

using d0-d4 as an example:
when d0 = d4 led is OFF
when d0 > d4 led is green
when d0 < d4 led is red
(i might have the green/red states reversed - prof Richter?)

My assumption regarding why Grant used this method is that it is a good indicator of CHANGE - which is the exact type of feedback the user needs to adjust probablility controls.
The compromise is of course that it is very hard to determine the exact state of the 8-bit register from this 4-led display. But (i likewise assume) devoting an entire 8-led subassembly and the requisite panel real estate for a direct register display would have been more costly. 
 The 'Goldberg jr.' that i gave Grant in July 2001 had an 8-led direct display but no clock or data indicators. I'm impressed with the efficiency and economy of the scheme Grant devised to get a lot of feed back to the user with just 8 lights and very low current consumption

Hope this helps you 'read' what your marvelous little gadget is doing.

Best,
-doc