Even a know-nothing dumbhiney like myself is interested in learning more.
Well, you have this little chip. Provide it 5 volts. They have a carrier board that has the voltage regulator on board, so you just plug in a 9v battery or one of those 'brick-on-a-rope' power supplies from your calculator.
You write a program (in a pseudo-basic kinda language) that tells the inputs or outputs what to do. For example, my clock program looked like this back in the beginning:
Set up variable space
DataP CON 0 ' Data pin to Displays.
Clock CON 1 ' Shift clock to Displays.
Latch CON 2 ' Moves data from register to output latch.
Minute VAR BYTE
Second10 VAR BYTE
Second1 VAR BYTE
DispMin VAR BYTE
DispSec10 VAR BYTE
DispSec1 VAR BYTE
Timer VAR WORD
Setpoint VAR WORD
Initialize the counter
Setpoint=180
For-Next loop
FOR Timer = Setpoint to 0
Do some modulus math to break seconds down into 3 digits for the display
Minute=Timer/60
Second10=(Timer//60)/10
Second1=(Timer//60)//10
This part was tricky. Using the numbers for the 3 different displays, clock the data out on a single pin (DataP-Pin 0 as defined earlier) as 24 bits, with the clock pulse on (Clock-Pin 1). When done, strobe (Latch-Pin 2) and the displays update. The displays
LOOKUP Minute, [191,134,219,207,230,237,253,135,255,239], DispMin
LOOKUP Second10, [191,134,219,207,230,237,253,135,255,239], DispSec10
LOOKUP Second1, [191,134,219,207,230,237,253,135,255,239], DispSec1
SHIFTOUT DataP,Clock,MSBFIRST,[DispMin,DispSec10,DispSec1]
PULSOUT Latch,1
Since all that only took 50 ms, wait another 950 ms before nexting back to the beginning.
PAUSE 950
NEXT
END
You get commands like IN to read the status of a pin, OUT to turn on/off an output, and a lot of other basic-type commands. Theres a few more like CASE that seem to be swiped from C.
Depending on what you want to drive with those outputs, you need some kind of interfacing circuitry. For 120v lights, I just use a solid-state relay with a 5v input. To control a solenoid (think Q-Bert's knocker - something needs to interface a fairly high current solenoid with the 5v logic signal from the PCB. A hefty transistor will do the trick.
Theres all kinds of sites out there on these critters. They are sweet for anything that needs to react to something. Not the most powerful processor, and they tend to be kinda slow in the overall scheme of things, but, hey, you can do some neat stuff for relatively cheap.
The displays I used were some surplus things from sports clocks or something. Got 'em for like $10 a digit. Heres the finished project: