The Multi-Mode Digital Voice Modem is a combined hardware and software development of a modem to handle all amateur digital voice modes. Initially it will support D-Star and DMR, with System Fusion and P.25 coming later, as well as a built-in FM repeater controller. For all modes other than DMR and FM, the modem can be used in simplex or duplex mode, while for DMR and FM full duplex must be used. The protocol between the modem and the host is new.
The hardware will typically be ARM based, with initial developments being aimed at the Arduino Due and Teensy 3.1, the STM32 range is also looking like a suitable chip, with the more advanced Cortex M4 architecture and higher clock speeds. The interfacing hardware will consist of op-amp low pass filters and level shifters.
Jonathan Naylor G4KLX GitHub