Given the commonalities I’m seeing for the various printheads (LVDS, shift registers, etc) maybe it’s time to start thinking about rolling our own pen controller electronics.
I would see the basic idea as a SPI bus to the electronics, along with a ‘dot clock’ line, and a ‘fire’ signal.
The connection from the electronics to printhead would be N bits of LVDS output.
The SPI bus would load up a SRAM ring buffer on the electronics with the line to print, N bits wide, by M dots, by F fires.
On every ‘fire’ signal, the next set of M ‘dots’ (N bits per ‘dot’) would be sent to the printhead at the ‘dot clock’ data rate.
The ‘fire’ signal could be directly connected to the microcontroller, or to one of the optical encoder outputs from the printhead carriage if using the DC motor + encoder from an existing carriage.