Intro to Controllers

Applications

Since these pages are nominally intended to foster extreme Halloween decorating, we consider the possible uses of intelligent controllers in a haunt.

• Automation of fine details

  As I have already mentioned, we like to control our haunt props ourselves. But this refers to the overall sense of hitting the "go" button.

  Let's say that we have a talking skull that recites a speech about eating little children. I want to be able to press a button labeled "menace the baby", and not have to worry about the fine details of finding and playing the correct sound track, opening and closing the jaws, and moving the head back and forth.

• Automation of repetitive sequences

  Commercial haunts have a concern about using fewer actors, sometimes augmenting a live staff with animated figures. A room may contain several props that are ready to perform at the push of a button, but they might still require a higher-level sequencing.

• Decision making and reaction to stimulus

  The simplest completely automated scare is some form of people-sensor that immediately triggers a prop. The patrons rapidly learn that if you step on a certain spot, the prop triggers. They will keep stepping there to enjoy repeat performances, and perhaps ruin the startle for the next visitors. This problem is usually addressed by use of a timer that prevents a prop from being re-triggered soon after it is activated.

  An intelligent control system goes well beyond this. It is capable of making much better decisions about when a prop should and should not be triggered. Unlike a dumb timer, it might pick and choose sequences or combinations of props, so that the experience is different every time.

• Orchistration of complex, sometimes far-flung, effects

  If you have ever been through Disney's "It's a Small World" ride, you know that their song plays continuously throughout the entire ride. In every different room, another set of characters sings the song, perfectly coordinated with the other characters throughout the ride, so that you hear a smooth transition from one set of voices to another as you pass between rooms.

  Through the use of a centralized control system, a haunt can be orchistrated, so that sounds washing over from other rooms are coordinated with ambient sounds.

Computers have gotten somewhat smaller since then.

Practical choices for haunt automation are:

• sequences through instructions (the "program")
• makes decisions
• performs math operations

In the early days of small computers, the CPUs were difficult to work with. Some required strange voltages or funky multiphase clocks. Some CPUs were partitioned into multiple chips.

Some early CPUs that were easy to hook up and get working were the 6502 and Z-80.

But a CPU by itself is not enough. You need to add components to make it a functioning computer. It has to have memory to contain the program, memory to store data, and input/output peripherals.

You could put together a nice little controller with a Z-80, EPROM, SRAM chip, and some jellybean logic chips for I/O.

I use "MCU" to mean "Micro Controller Unit". This is a single chip that contains most or all of the components necessary for a functioning computer, including:

• CPU
• ROM, to store the program
• RAM, to store data
• input/output port(s)
• support logic, such as clock generation and address decoding

Some notable MCUs are:

• Motorola's MC68HC11 family
• Microchip Technology's PIC family
• Atmel's AVR family

Don't confuse power with size. The 68HC11 (left) is much more powerful than the 8748 (bottom).

Please note the word "family" in all cases. Most MCUs are available in a plethora of different variations, each appealing to different user requirements. If you don't need much I/O, you can get an MCU in an 8-pin DIP package. If you need more ports, essentially the same CPU is available in larger packages, and with other peripherals.

Here are a couple Atmel AVR chips. The processors ave virtually identical, but the larger chip allows more input/output options.

This is Marvin Green's original BotBoard. It runs a 68HC811E2 microcontroller in single chip mode.

The components on the board are the bare minimum in order to get the MCU to run.

Since a lot of thought goes into the design of this hardware, they usually consider the software, too - and provide some sort of software operating environment.

This is a SBC from New Micros. The CPU is a Motorola 68HC11, with a FORTH environment on-chip.

Note the large 28-pin sockets on the left. These accommodate byte-wide RAM and ROM.

Since these are general-purpose computers, they can be programmed for whatever purpose is needful.

MORE SOON...

ld a, (lstout)
and NOT videna
ld (conport),a

NOTE: There is usually a close correspondence between the assembly program, and the machine language it turns into. In this case:

ld a, (lstout)  -> 3A 10 51
and NOT videna  -> E6 DF
ld (conport),a  -> 32 38 00

conport = lstout & ~videna

The above is the procedure that you would follow when programming on a bare PIC or Atmel chip. You program in C or BASIC, and the compiler translates it into the machine code. The machine code is run directly by the microcontroller.

• Real-time

  An intelligent control system that is able to accept input, figure out what to do, and act on it fast enough to make a difference to the process while it is happening. If your answer is correct, but late, it doesn't count.

  Note that real-time does not necessarily mean fast. One man's "real-time" is another man's "damned slow". It all depends on the process you are trying to monitor and control.

  The important characteristic of real-time system is that the processing time be predictable.

• Embedded

  An embedded processor is a computer built into something. You get bonus points if the computer enhances something where you least expect it.

  A calculator has a computer embedded in it, but it doesn't impress people much since you expect it to do computation. But if you have an espresso maker that is precisely controlled by a computer chip that you never even see - that's really embedded!