The Electric Crayon
Percom advertisement from the April 1980 issue of 80 Microcomputing
The Electric Crayon was a small (12 inch wide by 9 inch deep) box which output a composite video signal that could drive either a monitor or a television set. It connected directly to the TRS‑80 printer port and was controlled using EGOS, a ROM-based operating system. EGOS was directly programmed using single character commands. Virtually unique among TRS‑80 color add-ons, the Electric Crayon did not use the TMS9918 graphics chip and did not support sprites.
Ten video modes were available, including two semigraphics modes and eight graphics modes, but only two of them were possible with the default 1K of video memory. All ten modes were possible if the video memory was upgraded to a full 6K (Percom charged $29.95 for each kilobyte).
The maximum resolution was 256 by 192 and eight colors were possible: green, yellow, blue, red, buff, cyan, magenta, and orange. But only four colors were allowed at the higher resolutions and only two at the highest resolution. In semigraphics modes, a built-in character generator helped with displaying text.
The Electric Crayon was quite an impressive peripheral. Harold Mauch, the president of Percom, described it as “a complete, self-contained control computer with provision for 1K-byte of on-board program RAM, an EPROM chip for extending EGOS and a second dual bidirectional 8-bit port – over and above the dual I/O computer port – for peripherals.” But most of that promise remained untapped. Percom sold a few programs for the Electric Crayon but the software and games that might have taken full advantage of its features were never written.