A quick note..... Many of the pages here are incomplete or out of date. I will work on them when I get the chance. :)
~ January 2020 This is an MMDVM dual hat board. MMDVM stands for Multi-Mode Digital Voice Modem. The board sits on a Raspberry Pi and there is a great piece of software, Pi-Star, that allows for easy access and setup. The MMDVM will work with DMR, DStar, and Yaesu Fusion radios along with some others (NXDN, P25). Now, the Pi-Star name can be a bit confusing as it works with all of these modes, not just D-Star. The MMDVM will connect via the internet to hundreds of rooms where other stations may (or may not be). I have gone the Yaesu System Fusion route and use an FT-70D handheld to talk to the MMDVM/RPi/Pi-Star setup.
Update - November 2023 The MMDVM is still going strong. I have used it with DMR now as well as Fusion.