TSU Meeting SUNDAY — October 19, 2025

David Anderson, Carl Miles, Adam Trionfo, Ryan Gray, Tim Swenson, Johnny Red, Evan, Gustavo, John

Mid-month Sunday Zoom meeting (timed so Johnny Red could join from his time zone). David Anderson opened with a quick state-of-the-projects: the TS-Pico update is nearing completion (Ryan, Ricardo, Tim and others chasing down the last issues), and Jeff Burrell + Joe Vandezande are well into a modern recreation of the never-shipped Timex/Sinclair 2060 bus-expansion unit. With Jeff absent, the bulk of the meeting was a long Carl Miles show-and-tell of in-flight boards.

Carl walked through his TS1000/ZX81 "1520" super-expansion (two stacked boards: AY-3-8912 sound, IO decoding, programmable two-button DB9 joystick, LM386 amp/speaker, 512K RAM with jumper-selectable 8K banks and a writable shadow-ROM region, battery backup, and BOTH a TS1510 cartridge slot and a ROM cartridge slot keyed so they can't be cross-inserted, with auto memory-disable when a cartridge claims the 16–48K range). He then showed the rev 0.2a "KiloZ" / 1068 motherboard built to drop into Ingo's full-size keyboard case — a real Ferranti ZX81 ULA, ESP32 with sampled VGA output, AY sound, programmable joystick, 512K RAM, M1NOT switch with bicolor status LED, ear/mic + composite/stereo output. The rev 0.1 board had failed because new Mouser ceramic oscillators ran far below 3.25 MHz; Carl bought 100 of the original CTS part from China and the board now runs. He also showed a Spectrum +3 external drive-B project: the original 3" Panasonic mech in a community 3D-printed enclosure, with a very cramped sandwiched PCB carrying a 5V regulator and an IDC header, fed 12V over the ribbon so no external PSU is needed; he's putting a Gotek in the +3 itself.

More Carl boards: a TS2050/Westridge modem-to-RS-232 switching module that sits on the 8251 UART socket, using latching set/reset relays to flip six handshake lines between the on-board modem and a DB25, with a front-panel bicolor LED (red = 2050 modem mode, green = RS-232). This sparked a side discussion of WiFi "modems" (WiModem232-class devices that present a Hayes AT interface over Telnet/TCP) as the practical answer now that POTS lines are largely gone — Evan demoed one. Carl also showed a small TS2068 board that replaces the rear composite jack and adds true stereo line out by tapping the AY's A/B/C pins (auto-mutes the internal speaker when a plug is inserted), and a companion two-piece board that sits over the AY and over the +5V/op-amp "power supply" chip to disable the internal mono mix and kill the persistent hiss. Finally, the "Interface Zero" board: a from-scratch recreation of Wes Brzozowski's interface-zero glue combined with the full ZX Interface 1 (microdrive + RS-232 + Spectrum net), David's mini-DIN video output, and a 64K ROM bank switcher. Because the 2068 has no ROM-CS line on its bus, the design fully decodes the IO ports and uses bank-enable + diode logic to page the home ROM out for the Interface 1 ROM (and optionally a Spectrum diagnostic ROM). Charlie's FPGA Interface 1 ULA replacement would unblock production but currently can't ship to the US. A separate point from Wes's notes also came up: only D2 is pulled high on the 2068 bus, which is why some Spectrum programs crash when reading floating ports — the new board pulls all data lines high.

David closed by walking through the modern TS2060 bus-expansion board: Jeff Burrell's FPGA carrying Spectrum and (planned) ZX81 cores, a large RP2040 (Pico 2-class) plus a second small Pico for USB host (mouse/keyboard), stereo DAC, WiFi, SD card, RTC, VGA, and joystick/serial headers. Joe Vandezande is designing a 3D-printed enclosure mimicking the original 2060 shape with a front-bezel SD slot and a small OLED status display. Gustavo confirmed the software direction: extend the TPI command set so the device is driven through standard SAVE/LOAD with WiFi storage transparent to existing software, with CP/M and the FPGA's native 64/80-column modes as longer-term goals. Next meeting Monday November 3 at 9 PM Eastern; David encouraged seasonal type-in programs for the TS1000/2068 between now and the December meeting. John plugged the Chicago TI-99/4A group's one-day festival at Evanston library the following Saturday.

Highlights

Carl Miles walked through a "1520" TS1000/ZX81 super-expansion — AY sound, programmable DB9 joystick, 512K RAM, shadow-ROM region, and both a TS1510 cartridge port and a (keyed) ROM cartridge port on one stacked board.
Rev 0.2a of Carl's "KiloZ" / 1068 motherboard (real Ferranti ULA + ESP32 VGA, sound, joystick, 512K RAM) is built and waiting on a VGA/power dongle; rev 0.1 had failed because new ceramic oscillators ran too slow, fixed with 100 CTS parts sourced from China.
New TS2050 "Westridge" board uses latching set/reset relays to swap the 8251 UART between the on-board modem and a rear DB25 RS-232 port, with a bicolor front-panel LED indicating mode; intended to pair with WiFi-modem (WiModem232-style) devices now that POTS lines are scarce.
TS2068 stereo + composite jack-replacement board, plus a companion two-piece PCB that sits over the AY and the +5V/op-amp power-supply chip to give true stereo line out and kill the persistent internal hiss, both heading to JLCPCB.
David previewed the modernized TS2060 bus-expansion unit: Jeff Burrell's FPGA (Spectrum + planned ZX81 cores), Pico 2 + second small Pico for USB host, WiFi, SD, RTC, VGA, stereo DAC; Joe Vandezande designing a 3D-printed enclosure with bezel-mounted SD slot and OLED status display. Gustavo confirmed the software plan: TPI-extended SAVE/LOAD so existing software runs unmodified, with CP/M and native 64/80-column modes on the roadmap.

Projects discussed: TS1510 Cartridge Interface Clone · TS-Pico · "1068" — Enhanced TS1000 · FPGA "Advanced 2068" Topics: Hardware projects & new boards · TS2068 / TC2068 · TS1000 / ZX81 / TS1500 · Pico / modern interfaces (UnoDos, etc.) · Modems, serial & RS-232 · Video upgrades (composite, RGB, HDMI)

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