We were sitting around in the early 80's with an Apple II computer, wondering what to do with it.
This was a time when small microprocessor boards and speech synthesizer boards became affordable to young hobbyists. I'd seen the first issue of BYTE magazine and subscribed.
While playing around with the Apple II we found, in the magazine, a small (2.5" x 4.5" x 1/4"), inexpensive ( < $100 ), processor board with a 6502 processor (the same chip as the Apple II!), with room for a 2K or 4K ROM. We also found a cheap ROM burner.
The processor was about 2.5" x 4.5". The speech synthesizer board was a little smaller than that, and came with a microphone out jack. We decided to control it using 4 mercury tilt switches. The whole thing was powered by 4 x 1.5 volt AA size Nickel-cadmium batterys, unregulated.
We used the Apple II to write and test 6502 assembly language, and attached a ROM burner to program the ROM chip. The assembly code for our blackjack counting program was about 2K.
While we were testing the blackjack counting code I forget exactly how we did it, but recall having the two 6502 chips "talking" to each other (I imagine we used the serial ports and were banging directly at the 6502's registers, but I'd have to check). Anyway, the Apple II played the dealer and kept score, the little 6502 circuit board device we were building listened to the "dealer" and sent back blackjack decisions, such as how much to bet, when to hit, double down, split, or fold, through the voice synthesizer. This was loads of fun.
It doesn't take much to keep a geek happy.
The processor board fit in a breast pocket on one side of a suit jacket, the speech synthesizer on the other, earphone wire going up the neck, wires going around the back and down the pants to the mercury tilt switches that were in a pair of shoes, all connected to the batteries in the pants pockets.
Back then, this was fun.
The 4 switches could be used to produce 15 different basic signals. Signals 1 to 10 were used for the card values, 12 was to signal the dealers up-card was next, 14 was to signal the cards coming into your own hand. 13 was reserved for bad luck.
I recall we had to write a little extra code to "debounce" the signals coming in from the tilt switches.
0 was used as an "escape" code to get into setting things like the number of decks in the shoe, and to indicate when the deck was shuffled, and whether there were any special play options. Some casino's didn't allow doubling down on certain hands.
The machine and code were done in spare time over a summer vacation. As I recall it was tested to provide about a 1/2 percent edge on a 4 deck shoe. 4 decks was common. Casinos rarely did one deck back then because they knew there were people who could count in their head. This was back when Thorpe's book "Beat the Dealer" became very popular, and there were groups of people who went out and fleeced the casinos. That's another story.
Anyway, once we got this thing working we had to figure out who was gonna go off and try it out in a casino. That got interesting.
Several people started out very interested. They all gave it some thought, and decided they didn't want to end up at the bottom of a lake or river wearing cement boots, or buried somewhere under a freshly laid slab of concrete.
Still, it was fun learning to design and build. It was lots of fun to show at parties!