DroidStar: get on DMR without a radio — from phone and PC

Not everyone has a radio on hand. But if you have a callsign, a DMR ID and a smartphone, you can get on the digital air right now. DroidStar (by Doug AD8DP) is an open-source cross-platform client that connects to DMR servers and to reflectors of other modes over the internet, encoding your voice in software or through an external AMBE device. No radio, no hotspot — just an app and a network.

What DroidStar can do

The app supports several digital modes at once:

• DMR — via the homebrew protocol (the same one used by Pi-Star/WPSD hotspots);
• YSF / FCS — Fusion, DN and VW modes;
• D-STAR — REF, XRF, DCS reflectors;
• P25 and NXDN;
• M17 — with the open Codec2 vocoder.

It runs on Android, Windows, Linux and macOS. On Android, DroidStar is available on Google Play. The source code is open on GitHub under the GPL license — written in C++ with Qt.

Vocoder: hardware or software

DMR uses the proprietary AMBE+2 codec, protected by DVSI patents. DroidStar solves this in two ways:

Hardware AMBE device

A USB stick with a DVSI chip (ThumbDV, DVStick 30 and similar) plugs into the computer and performs the encoding in hardware. This is the de facto standard route on a PC: reference quality, minimal latency. On Android a USB stick also works through an OTG adapter, but not on every phone.

Software vocoder (plugin)

For Android and embedded platforms (including Raspberry Pi on ARM), DroidStar supports a loadable vocoder plugin. The plugin is downloaded via a URL right from the app's settings. On ARM platforms you can use the MD380 vocoder.

Practice shows that for communication over a private network with the software plugin the quality is quite acceptable. Noticeable degradation only appears with a weak internet connection — not in the vocoder, but in the buffering of UDP packets.

Setting up DroidStar for DMR

Let's go over the minimal set of parameters for connecting to a DMR server. The interface is the same on all platforms.

Main fields

• Callsign — your callsign (in capital letters);
• DMR ID — your registered digital identifier; without it the server will reject the connection;
• Mode — select DMR;
• Host — the DMR server address (for a private network, entered manually);
• TG — the talkgroup number you go out on;
• Slot — the timeslot (usually 2 for simplex);
• CC — Color Code (must match the one set on the server).

Connecting to a private network (homebrew)

DroidStar uses the same homebrew protocol as MMDVM-based hotspots. To connect to a DMRhub server, you need to enter the master server address in the Host field manually — there is no built-in host list for a private network in the app. Check the host, port and password of the homebrew connection in the network's personal dashboard.

Host:    dmrhub.ru
Port:    62031
Password:  (from the personal dashboard)
TG:      (network group number)
Slot:    2
CC:      1

Installing the vocoder plugin (Android)

1. Open the Settings tab in DroidStar.
2. In the Vocoder URL field paste the plugin link (taken from the project README on GitHub).
3. Click Download vocoder — the file is saved automatically.
4. Restart the app.

On Linux the plugin is placed manually into ~/.config/dudetronics/, with the file name vocoder_plugin.linux.x86_64 (or .arm64 for ARM).

MMDVM-modem mode: DroidStar as a hotspot

If an MMDVM modem (MMDVM_HS_Hat or similar) is connected to the computer, DroidStar can act as the software part of a hotspot. In this mode you select the MMDVM device in the Modem field, and the app starts serving ordinary DMR radios over RF — that is, it becomes an equivalent of Pi-Star, only without a Raspberry Pi.

This is handy for debugging: plug the modem into a laptop, launch DroidStar, confirm that the radio hears the hotspot — and then move on to sorting out the config or calibration.

DroidStar vs the native DMRhub app

DroidStar is a universal client for many networks and modes. It's great for trying out the digital air or for working with several networks at once. But it has no integration with a specific network: no authentication, no operator contact lists, no private SMS and no group messages.

For everyday work specifically within the DMRhub network there is a native Android app — it was built as a client for our network with a full set of features: account-based authentication, network operator contacts, private and group SMS, Push-to-Talk. If you're a DMRhub member, this is the main tool.