Old cash register display restored on VGA with Pi Pico

When a Samsung SPS-1000 cash register lost its monochrome STN display, a replacement priced near $300. A maker captured its SED1351 controller signals, decoded the four-bit data bus and displayed the 320 x 240 image live on a VGA monitor using a Raspberry Pi Pico.

Old cash register display restored on VGA with Pi Pico

Key points

  • An oscilloscope can reveal the signals needed to understand an obsolete display interface.
  • The recovered controller data produced a real-time 320 x 240 image on a standard VGA monitor.
  • A Raspberry Pi Pico provided a more stable result than the earlier STM32F407 prototype.

Context

The project shows how affordable microcontrollers can preserve access to aging hardware without altering the original cash register. Its practical relevance lies in reverse engineering legacy peripherals and integrating them with current display systems.

What this means for you

Directly applicable

Developers can use the signal-capture and bus-decoding approach to connect obsolete peripherals to modern displays while leaving the original device operational.

Who benefits: Developers maintaining legacy hardware benefit when they need to understand an undocumented display controller and connect it to contemporary equipment.

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