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Timex Sinclair User Group Meeting with European Friends — May 15, 2022

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David, Adam Trionfo, Jeff Burrell, Ingo, Tim H, Ryan Gray, Stewart Newfeld, Alan, Joao, Don

David walked through his ongoing TS2068 ROM disassembly project, built on top of Alvin Albright's Word-document disassembly and Wes Brzezowski's Time Designs analysis of the bank-expansion ROM, and now aided by a 90-page "Timex programmers' super-secret document" Jeff Major surfaced (uploaded to archive.org). The discussion got into the X-ROM's bank-switching gymnastics, the 4000/8000/A000/C000 register windows for the never-shipped bank-expansion unit, the unused Pascal cartridge-type byte, and the literal jumper-X on the motherboard for selecting mask ROM vs. EEPROM. Jeff confirmed the document made the tape routines and bank-switching code much easier to read.

Keyboards dominated the middle of the meeting. Ingo showed a mechanical-switch ZX81/TS1000 replacement keyboard plus a new breakout-board approach that interfaces through the expansion port — he replaced the missing 74LS365 hex bus driver with a GAL programmed to do the same A0/RD/IORQ-gated tri-state output. Tim (in New Zealand) showed his custom WASD keycaps on a Keychron 60% board, an internal USB and HDMI mod for his ZX81, the "Babble Key" USB-to-ZX matrix adapter (using Hoglet's RGB-to-HDMI Raspberry Pi project for video), and an X-modem-style high-speed loader over the USB serial link. Stuart pitched the Ginger Electronics PCB keyboard replacements (tactile switches + membrane overlay) for ZX81/TS1000/TS1500 and ZX Spectrum, available near cost to the group, and floated the idea of an iPhone/Android app to replace the cassette recorder for loading.

Jeff Burrell reported proof-of-concept communication between a TS2068 and a Raspberry Pi Pico — opening files on an SD card from the 2068 — and is now laying out the PCB for the interface, partly because the obsolete parts he's relying on are starting to disappear from Digi-Key. David shared Stewart Newfeld's old S-100 6-bit D/A music board, prompted by a podcast where Dorothy Siegel (clarinettist who played duets with Stuart's board in the late '70s) discussed his work.

The group closed on speech synthesis — Tad Painter's Speech Synthesizer 2068 (273 sampled words; Adam confirmed the whole tape now loads, and embedded MP3 demos and a video on the site), the Zebra Talker for the ZX81 (SC01 Votrax driven by the NBS text-to-phoneme rules), and the SPO256 / General Instruments speech chip Tim Swenson's mystery box turned out to use — and on tape preservation: pencil-turn the capstan to detect sticky binder, clean the head every pass, transplant sonic-welded shells with a screwdriver-and-rag trick, and only bake the tape as a last resort. Next meeting is Monday June 6.

Highlights

  • David's TS2068 ROM disassembly leveled up by Jeff Major surfacing a 90-page Timex programmers' document, now on archive.org
  • Ingo's GAL-based external-keyboard interface for ZX81/TS1000 via the expansion port (replacing a 74LS365)
  • Tim (NZ) demos custom WASD keycaps, Babble Key USB-to-ZX adapter, and Hoglet's RGB-to-HDMI video upgrade
  • Jeff Burrell has a TS2068 talking to a Pi Pico + SD card; now laying out the interface PCB
  • Tape-archiving guidance: pencil-test the capstan for sticky binder, clean the head every pass, replace the shell rather than baking

Projects discussed: UnoDos · Library Tape Archiving Process Topics: TS2068 / TC2068 · Hardware projects & new boards · TS1000 / ZX81 / TS1500 · Machine code, Z80 & assemblers · Pico / modern interfaces (UnoDos, etc.) · Tape & library archiving (TAP/TZX)

Summary generated from the meeting recording; the full transcript is kept in the group's private archive.