I hope I am not repeating any post with this. Actualy I know little to none about DRO but this info caught my attention, I hope it will be interesting to you.
Somewhere in the mid page in this link:Milling Machine Robust Digital Readout
By Scott Nortman and Scott Kanowitz
This project outlines the development of a four-axis digital readout for a milling machine. It uses SPI-connected quadrature decoders along with a touch-input LCD connected to a PSoC to make a robust machine display interface.
Milling Machine Robust Digital Readout