Controller board

The controller PCB and printhead adapter board are maintained in a separate KiCad project. The adapter connects the controller to the printhead's flex connector.

Maintained separately

The KiCad project is not in any of the Paintress repositories. The pinout the firmware expects is in its config/board_config.h; the firmware is not published yet.

Origin and methodology

The board was developed through independent reverse engineering using oscilloscope measurements, signal analysis and public references such as textbooks, application notes and descriptions of generic components. No datasheets, proprietary documentation or firmware were used. The project is not affiliated with or endorsed by a printer manufacturer.

High voltage

The hardware runs at up to 42 V DC into reactive loads (piezoelectric elements) and has not been certified to any safety standard. Incorrect assembly, modification or operation can cause electric shock, component damage, fire or damage to connected equipment. Read Safety before building or operating the hardware.

What the firmware expects of it

The board uses an RP2350-class MCU and 8 MB of external PSRAM on XIP chip-select 1. PSRAM is required for swath buffering; if initialisation fails, the firmware halts and flashes the LED rapidly. The head connections include the PIO data bus, window selector, DAC, device enable and DAC standby/reset lines. The board also receives the start trigger.

The DAC standby and reset lines need hardware pull-downs. The firmware drives them LOW at the start of main(), but only the board can keep them low between power-on and that first instruction.

Wiring

The RP2350 GPIO assignments for the printhead interface (data bus, window selector, DAC, enable, start trigger) are defined in the firmware's config/board_config.h (not published yet).