TSU Meeting MONDAY — January 6, 2025
David, Dave Franson, Adam Trionfo, Christian, Joe Andy, Carl Miles, John, Tim Swenson, Ryan Gray, Gustavo, Paul, Peyton, Jay
Guest Dave Franson (formerly of the Sinclair Milwaukee Users Group, SMUG) opened the meeting with his origin story — a 1982 TS1000 from a Wisconsin grocery-store promo, a 2068 soon after, and a tech-demo he wrote called Extended Paint that exploited the 2068's extended color mode for higher horizontal color resolution. He had recently rediscovered a cassette of the program, which David will digitize. The group also reminisced about the SMUG digitizer board (video-input still capture) and looked at period digitized headshots and View 3D renderings.
Joe Andy showed a board he built that adds a contiguous 48K of static RAM to a ZX81 to run a 48K version of Sponzie (a Spectrum-flavored 16K replacement ROM for the ZX81). The design is an amalgam of two Wilf Rigter memory-mapping circuits; current prototype uses a 128K RAM + decoder, with a slimmer 64K-CMOS-RAM revision in progress. Board files were uploaded to the shared Google Drive. Carl Miles followed with a closely related project: a ZX81 internal expansion board combining HRG support, the M1-NOT mod (machine code above 32K, via Derek's A14/A15 ULA-line interception), and contiguous RAM from 16K to 48K so MemoTech-style relocated HOT-Z fits. The 16-48K placement conflicts with the 1510 cartridge address range, so Carl is considering moving the RAM onto a cartridge board instead. Carl also has new revisions of his ZX81 ROM-replacement board and his 1510 cartridge clone (with the BCD/seven-segment display, four-megabit EEPROM, multi-program dip-switch select) in hand and will build them up soon. Kevin helped fix the Windows/Mac builds of the TAP-to-cartridge converter; binaries are now on GitHub.
John demoed a TS2068 dual-display-file animation engine he wrote over the holidays as an experiment in AI-assisted Z80 code generation. Four image buffers are pre-allocated; an LDIR-based routine copies each frame into whichever display file (1 or 2) is currently hidden, then flips port 255 to swap which is shown. He showed three animations (Juggler, Snake, Grid) — David ran them on real 2068 hardware via TS-Pico. Gustavo described the proper interrupt-synchronized flip technique (catch the IM via the XROM dispatcher, halt to vertical refresh, then toggle the display-file bit on port 255) to avoid visible tearing. David gave a TS-Pico status update: the new 1.1c firmware is reliable thanks to bug-squashing by Ryan and Ricardo; upgrades will work by copying a folder to the SD card; the code will be open-sourced on GitHub; and the team plans to implement an RST 8 / on-error hook so the Pico can intercept BASIC commands the way the Interface 1 and the Portuguese Zebra FDD do on Spectrum/2068.
Tim Swenson previewed an article on doing 512×192 graphics in OS 64 — the cartridge supports the high-res mode but ships no graphics primitives, so Tim worked out the memory layout, wrote PLOT for both 32- and 64-column modes, and ran Bresenham line and circle on top. Tim also confirmed Sinc-Link issue 16-11 is at the printer: 24 pages, 11×17 glossy saddle-stitched, 75 copies, paid for from the Bill Miller collection fund. Ryan Gray showed a calendar program he recomposed from an 1986 printout (he hadn't yet recovered the original tape) using the Fort Worth user-group calendar-calculation routine and a stacked double-height font; he prints by capturing the emulator's PBM output and running it through ImageMagick to PDF. Christian (Kentucky) brought a flaky TS2068+TS-Pico setup; the group diagnosed his SD card as the culprit (likely a format/folder-layout issue, to be resolved offline). The next meeting is Sunday January 19 at 2 pm Eastern; David is trying to track down Sue from the Boston Computer Society Sinclair group as a future guest.
Highlights
- Guest Dave Franson (ex-SMUG, author of Extended Paint for TS2068) recovered a cassette of his program and will get it digitized.
- John demoed a TS2068 dual-display-file animation engine (Juggler / Snake / Grid) written with AI-assisted Z80 code generation; runs on real hardware via TS-Pico.
- Joe Andy built a contiguous 48K RAM board for the ZX81 to run a 48K Sponzie; Wilf Rigter–derived design, board files shared.
- Carl Miles has new revisions in of his 1510 cartridge clone and ZX81 ROM-replacement / HRG+M1-NOT expansion boards; build batch incoming.
- TS-Pico v1.1c is reliable; SD-card-based field upgrades, source going to GitHub, and an RST-8 hook is planned to intercept BASIC commands.
Projects discussed: TS1510 Cartridge Interface Clone · TS-Pico · TAP-to-Cart — TS2068 Cartridge Conversion · "1068" — Enhanced TS1000 Topics: TS2068 / TC2068 · TS1000 / ZX81 / TS1500 · Cartridges, EPROM & dumping · Hardware projects & new boards · Pico / modern interfaces (UnoDos, etc.) · Machine code, Z80 & assemblers
Summary generated from the meeting recording; the full transcript is kept in the group's private archive.