The Maximite computer, described in SILICON CHIP in March, April and May of this year has proved to be an unprecedented hit. By now over a thousand Maximites of various types have been built by enthusiastic readers.
Altronics has struggled for months to keep up with demand for kits, with each production run being sold out even before it was ready for sale.
The urge to play with the Maximite was so strong that it led many constructors to make their own PCBs or load the firmware onto Microchip evaluation boards or wire up their own breadboards.
The demand has also led to a growing Maximite ecosystem which even includes a number of Maximite clones (with approval, of course) from Dontronics (www.dontronics.com).
You can tell that you are popular when companies clone your creation; after all it happened to IBM with the PC clones, so why not SILICON CHIP?
Other companies have developed plug in boards and other accessories. For a full list of Maximite resources see the panel on page 38.
The readers who embraced the Maximite fell into one of three broad categories: they wanted to build a small computer and learn programming, or they wanted to use the Maximite to control something such as a home automation system. The final group just wanted to revisit the nostalgic days of yore when the Tandy TRS-80 and Commodore 64 dominated the personal computer landscape.
The miniMaximite described in this project is designed for the middle category of readers – those who want to embed the Maximite in a larger system as an intelligent controller.
Because the miniMaximite is 100% software compatible with its larger cousin you can develop your program on the full Maximite and when you are ready, copy the program to the miniMaximite and plug it into your circuit.
The “original” Maximite
Just to recap for readers who missed the Maximite articles – the Maximite is a small computer running a full featured BASIC interpreter including floating point numbers, string handling, arrays and much more.
The Maximite features a built-in VGA or composite video output and input from a standard IBM PS/2-compatible keyboard. It also has a USB interface for communicating with your PC and loading new versions of the firmware.
All you need to do is plug in a monitor, keyboard and 9V power pack and you are immediately ready to start writing your own program. You can type it in, test it and then save it to the built in SD card interface, all on the Maximite without the intervention of a larger computer such as a PC.
The Maximite also has also 20 input/output lines which can be independently configured as analog inputs, digital inputs or digital outputs. You can measure voltage, frequencies, detect switch closure etc and respond by turning on lights, closing relays etc – all under control of your BASIC program
All of this is accomplished using a single low-cost chip!
At a glance . . .
Processor: PIC32MX795F512H-80I/PT (or PIC32MX695F512H-80I/PT)
Clock speed: 80MHz
RAM: 128K (internal)
Software: MMBasic (similar to Microsoft BASIC)
I/O pins: 20, individually configurable
Video output: Monochrome standard VGA or composite video
Audio: 500mV for amplifier, sound card, etc, or hi-z speaker
Interfaces: USB 2.0 and IBM keyboard
Power supply: 2.3-3.6V DC @ (125mA plus peripherals)
Size & weight: 78 x 38 x 10mm; 15g
The idea behind the miniMaximite is simple: to shrink the Maximite down to the size of a large postage stamp while keeping it 100% compatible with the larger version in its external I/O capabilities and programming language.
The only items that the miniMaximite is missing are the connectors for the VGA, keyboard, sound and SD card. You can add them to the miniMaximite if you wish; the signals are brought out onto header pins. But we expect that usually, the miniMaximite will be driving an LCD or indicator LEDs and using pushbuttons for inputs.
For this reason you should not think of the miniMaximite as a replacement for the full sized Maximite. It is a minimalist version designed to add intelligence to your next creation.
In fact, you should have both Maximites: develop your program on the full Maximite and when you are ready, copy the program to the miniMaximite embedded in your circuit.
The best part is that they’re cheap enough to enable you to do this!