Yes, kit 24 is finally out! I hate real time. ;-(
I've been buying the Gakken Otona no Kagaku kits "after the fact". That is, they come out, I learn about them, and when I go to the store, they're already there on the shelves. In fact, there's still 5 kits that I don't have, and they're all back issues (well, yeah, obviously), so I can buy them whenever I want. But, I learned about the microcomputer kit from the wire recorder book at just about the time the wire recorder came out, so I've been anticipating this one for 3 months. I was going to the local bookstore every day for the last week, just in the hopes that it might come out before the official publication date of June 30. No such luck. But, two days ago was June 30, and there it was on the shelf. I didn't even break my stride in getting from the door to the register.
GMC-4, kit #24, 2500 yen
The "GMC-4" is Gakken's latest release in the "Adult Science" mook line. The model number means "Gakken Microcomputer, 4 bit". As a kit, there's almost nothing to it. 4 parts and 6 screws. The speaker is pre-wired to the circuit board, and assembly consists of screwing the speaker and board to the base plate, then attaching the plastic keypad to the circuit board with the double-sided plastic insulator. That's it. 5 minutes, tops. Oh yeah, the kit runs on 3 AA batteries, so you have to put the batteries in, too... Physically, the finished kit is about 2" x 5" x 3/4" - about the size of a PSP.
The key switches are the resistive type, triggering when you press the plastic "key". There's a plastic separator with little cutout holes where the "keys" go, and when you press a "key" your finger pushes the cover plastic down onto the conductive lines of the circuit board through the cutout hole and the circuit sees this as a closed switch. The point of all this is that the cutout holes are a bit small, so the switches aren't as easy to press as I'd like. It may be better to use an exacto knife to enlarge the holes a little bit to make the keypad more responsive (or maybe just add an external keypad).
This kit is great! I love it. It's a 4-bit microcomputer with a hex keypad, 4 control switches (A SET, INCR, RUN and RESET), a 7-segment LED, 7 regular LEDs, speaker, a hard reset switch, and an on-off switch. There are 7 pre-stored games, plus code in the mook for 10 other programs. There are 15 machine instructions, plus 16 "extended codes" that use the "E" code to allow for 2-byte instructions (E0, E1, E2, etc.) So, the instruction set is fairly straightforward, but you can still do some sophisticated manipulation of the LEDs and speaker. There's enough memory to hold a 64-byte program, and 16 bytes are set aside for data space.
The pre-loaded games include a "piano", a reflex game, and so on. The code in the book includes a 15-second counter and a rock-paper-scissors game. It looks like the GMC-4 is based on Gakken's FX-150 micro kit. The website has a link to the FX-Maicon's (R-165) user manual, and a lot of the programs in it are the same as for the GMC-4.
Code entry is very straightforward. Press RESET to zero the address counter, then press the desired hex key, followed by INCR. Press RESET-1-RUN to execute. To review your code, just press RESET and then INCR to increment through it. To play a pre-loaded game, press RESET, the code for the game (i.e. - '9' for the piano) and then RUN.
The pre-loaded games are:
9 - Piano
A - Music player
B - Tone repeat game
C - Whack-a-mole
D - Tennis
E - Timer
F - Morse code generator (described only in the FX-150 manual)
The other programs are:
Another LED flasher
Pulse width modulator
Another Music Player
Sequence Music Game
Gun fighter game
The mook is a little different this time, in that all of the articles are subject-related. Previous mooks included unrelated articles on WW II history, how to make your own beer, making a light bulb, and so on, plus articles related to the kit's subject. For kit #24, the articles include the history of computers, photos of older micro- and home-computers and video game consoles, an explanation of how chips are made and how they work, the process behind designing the GMC-4, and then the instruction set. The photos are all high-quality color, and it's a kick seeing pictures of machines that I used to own (including the old Altair 8800 box. Man, that takes me back.)
The kit is a bit clunky for program entry and there's no static data storage, meaning that you lose your program when you power it off. So, it's probably not going to get a lot of use once the novelty wears off. But still, for $25 it's a great value. Plus, the mook shows details for modding the premium wind-up tea carrying doll to turn it into a motorized robot with the GMC-4 as a controller, plus how to mod the GMC-4 to control up to three SX-150 synthesizers through their external input jacks.
Personally, I'm planning on adding a jack to plug in my headphones, plus a volume control (the speaker is too loud to play the games when everyone else is sleeping). I may also look at using the GMC-4 to control my synth keyboard setup.
The instruction set is going to take a little time to translate, and it's a bit on the long side, so I'll probably create a knol for it. Suffice it to say that that's going to be written up later. But, in summary, this is a fun little kit for anyone wanting to play with a simple hex-entry computer. Don't expect much of a challenge assembling it - it's all about the programs you end up writing for it.
FYI - Kit #25 is going to be another 35mm reflex film camera, due out in October (probably September 30).