80-COLUMN SERIAL VGA CARD (Propeller Version)

Modern 80-column text display expansion for the Coleco ADAM via the side expansion port (60-pin card edge). Pairs a vintage Signetics SCN2651C USART (NOS, 1983 date codes) for serial protocol conversion with a modern microcontroller that generates 80-column VGA text output through a DB-9 VGA connector.

Both versions share the same core architecture: the ADAM's Z80 writes character data through the expansion bus to the SCN2651C USART, which serializes it to the video processor. The microcontroller maintains an 80×25 character frame buffer and generates real-time VGA output — giving the ADAM a proper 80-column text display comparable to CP/M business terminals of the era, using silicon that didn't exist when the ADAM was manufactured.

Key ICs: Signetics SCN2651C Enhanced Programmable Communication Interface (28-pin DIP, NOS 1983 date codes), Parallax P8X32A Propeller 8-core MCU or Raspberry Pi Pico RP2040 dual-core ARM Cortex-M0+, 5.000 MHz crystal (USART baud rate reference), 74-series TTL support logic. Professional PCB with silkscreen, solder mask, and plated through-holes.