This 1802 MemberCHIP Card Computer Is Incredibly Small and Curiously Minty
DIY eight-bit computer kit fits inside of a small Altoids tin.
Building a small computer is a fantastic way to learn about these ubiquitous devices. In the case of Lee Hart's 1802 MemberCHIP Card computer, it is a tiny computer you build yourself. The eight-bit device fits inside a small Altoid mint tin!
The 1802 MemberCHIP Card Microcomputer measures 55 x 35 x 15 millimeters. The printed circuit board requires clever soldering to fill both sides with components. Despite its diminutive stature, the 1802 MemberCHIP is a full-featured eight-bit computer.
Hart based the design on the RCA 1802 microprocessor. Originally RCA introduced this eight-bit processor as the COSMAC (Complementary Symmetry Monolithic Array Computer). Today, most people just call it the RCA 1802. They are not difficult to buy, but they are no longer manufactured.
In the 1802 MemberCHIP computer, the processor runs at four Megahertz and has 32 kilobytes of RAM and 32 kilobytes of (UV) erasable programmable ROM (EPROM). However, unlike modern micros, the 1802 has neither memory built-in, so the MemberCHIP relies on discrete ICs.
Early eight-bit computers usually had two programs in their ROM. One was called a "monitor," which allowed the user to view (and change) memory content via a command line. And the other was some form of the BASIC programming language. Hart managed to fit both into MemberCHIP's ROM. Additionally, there is a built-in game called Adventureland!
For I/O, one pin is dedicated to output, and four pins are dedicated to input. The output and (one of the) input pins are for a 4800-baud serial interface for the 1802 MemberCHIP. These also have LEDs to indicate serial traffic. An additional 20-pin header acts as an expansion bus.
The 1802 MemberCHIP comes as a DIY solder kit. Hart hopes to capture the imaginations of younger tinkerers. For example, the instruction manual for assembling the computer is a tale about Alice in Micro-Land!
In addition to these features, the 1802 MemberCHIP card runs on less than 3 milliamps (when the LEDs are not on) and offers a hint of curiously strong peppermint when installed inside its case.
Check out this project page for additional (coming soon) details. Additionally, you can purchase an 1802 MemberCHIP here for $29.95.