Dr. Scott M. Baker Gives a Classic Grid Compass a Voice — With the World's First GPIB Speech Synth
The rugged laptop made famous by NASA — and Aliens — can now speak its bubble-memory mind, for the first time.
Vintage computing enthusiast and maker Dr. Scott M. Baker has given a classic Grid Compass laptop a new lease on life — and has even given it a voice, courtesy of a custom speech synthesizer add-on.
"The Grid Compass has been on my most-wanted list for a while because it is an early computer that makes use of magnetic bubble memory," Baker explains. "I've restored other bubble memory computers, such as the Teleram Portabubble. I've added bubbles to my RC2014 projects. I built a standalone basic bubble computer. I added bubbles to my Heathkit H8 and to my Multibus computers. I've done lots of bubble projects, but the Grid Compass was the standout that was missing."
Released by Grid Systems Corporation in 1982 and designed by Bill Moggridge, the Grid Compass was a rugged portable computer built with extreme environments in mind — with early buyers including NASA, which deployed it on Space Shuttle missions. Going toe-to-toe with the Osborne 1, the Grid Compass employed a more familiar clamshell layout and an almost-laptop-like compact-by-comparison chassis design, but lacked an internal battery. Perhaps its most famous outing was to the colony of Hadley's Hope on the planet LV-426 in the classic sci-fi film Aliens, where its glowing screen was seen controlling automated turrets deployed by the Colonial Marines — an echo of its real-world use by the US military.
Baker's example was purchased from a poplar auction site, and initially appeared non-functional with an unusual checkerboard pattern appearing on the screen. A reboot brought up a Microsoft MS-DOS 2.00 installation, stored in the non-volatile bubble memory, but cold-boots would always fail — a problem that was initially blamed on a faulty power supply but then traced to operator error: "I had left the power switch set to 200V instead of 110V," Baker explains. "Always check that first!"
With a working Grid Compass on-desk, Baker decided to expand it with a trademark add-on: a speech synthesizer, built as an external board connecting to the machine over the Hewlett-Packard General Purpose Interface Bus (GPIB), more properly known as the standard IEEE 488.1. "The GRiD Compass used GPIB for several peripherals including disk drives and printers. This provides me with an easy avenue for adding a speech peripheral. I'll make it a GPIB device," Baker explains, "and I'll leverage the Grid's built in GPIB printer support. To make the GRiD talk, we'll merely have to send text to LPT1."
The finalized design adopts a modular approach, accepting a speech synthesizer that can be built around a range of different voice chips. Not everything is period-appropriate, though: control logic is handled by a Raspberry Pi Pico 2 W microcontroller board, which accepts GPIB signals from the Grid Compass and translates them to instructions for one of three speech synthesizer boards: one based on the General Instruments SP0256, another on the Votrax SSI-263, and the third on the Votrax SC-01A, while a fourth dummy board scrolls phonemes across a six-digit hexadecimal display for diagnostics and bring-up.
More information is available on Baker's blog; schematics, production files, and firmware for the speech synthesizer are available on GitHub under an unspecified open source license.