Customized Keyboard Encoders

By eweek  |  Posted 2004-06-14 Print this article Print

You have many excellent alternatives to a keyboard hack available to you today. When I first became interested in this hobby five years ago, keyboard hacks were the only way I knew of to use the keyboard port for arcade controls. In fact, there were other possible solutions, but no one had put them and arcade controls together at that time. Since then, not only have vendors with suitable products been discovered, but several cottage industries have sprung up solely to serve the home arcade cabinet industry! In the rest of this chapter there are many keyboard-port based interfaces you can choose from. Theres even one you can build yourself! All of the following interfaces are custom keyboard encoders suitable for interfacing arcade controls via the keyboard port. Each has a set of features addressing some or all of the problems associated with keyboard hacks. They appear to the computer to be a regular keyboard, and are available in prices ranging from $27 up to $140, with the higher priced models supporting extra features. The next few sections cover the highlights of each model.
Pouring over the next several sections covering 13 different keyboard encoders may prove a bit daunting. I suggest reviewing the comparison chart in Table 8-1 first, and then reading the full details on those encoders that catch your eye. Its difficult to put all the important details into a single chart, however, so I encourage you to at least skim the introduction to each encoder.
Tip The chart and encoder descriptions that follow refer to matrix mode and direct mode inputs. Matrix mode refers to a keyboard matrix as described in earlier sections. Direct mode indicates the encoder is using a single pin for each input with no matrix involved, and hence no ghosting possibilities. Table 8-1: Keyboard Encoder Comparison Chart
Name Cost Number of Inputs Programmable Extra Features
ButtonBox $35-$50 Direct: 27Matrix: 128 Yes No
Hagstrom KE18/KE18 MAME $45 Direct: 18Matrix: 81 No No
Hagstrom LP24 $80 Direct: 23Matrix: 144 Yes No
Hagstrom KE24 $100 Direct: 24Matrix: 144 Yes Mixing direct and matrix modes
Hagstrom KE72/KE72T $120-$140 Direct: 72 Yes Trackball interface add-on
KeyWiz Eco/Max $27-$35 Direct: 32 Yes Shazaaam! key (shift key)
MAMI 24/48 $53-90 Direct: 24/48 No No
MK64 $63-108 Direct: 24 Yes Rotary joystick support; shift key
Ultimarc I-PAC2/I-PAC4/Mini-PAC $39-$69 Direct: 28/56/28-36 Yes Built-in programming; shift key
The ButtonBox The ButtonBox is a build-it-yourself keyboard encoder project designed specifically for interfacing arcade controls. It was designed and made available online by an arcade cabinet enthusiast. It supports both direct mode and matrix mode configurations. It handles up to 27 inputs in direct mode and 128 inputs in matrix mode. Assuming you have the tools, building the ButtonBox will cost you between $35 and $50 depending on how you build it. It consists of two separate components: the main CPU card, and the direct or matrix-mode daughter card. You will have to determine in advance how you want to configure the matrix or direct mode, as you will physically construct the daughter card to match your needs. There is no one-size-fits-all daughter card in the design specifications. For instance, if you create an 8 x 8 matrix for 64 inputs, and decide later you want an 8 x 16 matrix for 128 inputs, you will have to build a new daughter card. The design is a well thought out one, however. As far as wiring goes, follow the plans for the boards in order to end up with screw-down terminals that are easy to connect to. Programming the ButtonBox requires constructing a special parallel cable to connect to it, and then running the programming software. Programming cannot be loaded or saved from disk, and must be done interactively with the encoder. The programming software can be run within DOS or Windows. The ButtonBox is an interesting home-brew device and has appeal to those who are building an arcade cabinet for the challenge of it. It is included here for those of you who fall into that category. However, the complexity of construction and the costs involved in gathering all the needed components make this impractical for most people.


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