UltraEdge is building toward a modular radio control system: one where the controls you know — the feel of your gimbals, your switch layout, your case — can stay in your hands while the interface, computing and RF evolve. The Android companion is the first practical step, and UE Protocol is the documented radio↔companion interface it speaks. The public specification, reference codec and tests are a starting point for anyone building a compatible implementation. Today the protocol defines the radio-to-companion link only; interfaces for UltraEdge's proposed future hardware modules (processing daughterboard, power, I/O, RF, display) have not yet been designed.
Embedded-safe C++11 codec for the radio↔phone link (USB-CDC). Same source compiles into EdgeTX firmware (Cortex-M) and builds standalone for host tests/CI. No dynamic allocation, no exceptions, no RTTI, no external dependencies.
The wire format is authoritative in include/ultraedge/protocol.h —
that header is the spec any implementation must match. The implementer-facing prose spec (framing,
handshake, link-state gating, message catalog, conformance) is in SPEC.md.
Implementing it elsewhere or embedding it? See CONTRIBUTING and add your project to ADOPTERS.
What the protocol enables: the UltraEdge app driving an EdgeTX radio over USB.
The current protocol is v4 (PROTO_VERSION = 4), as used by UltraEdge firmware v1.0.2 and app v1.0.7
or later. Peers negotiate the version in the handshake; match the protocol version and capabilities of
your target release.
include/ultraedge/protocol.h public API + wire definitions
src/protocol.cpp codec implementation
tests/test_protocol.cpp dependency-free unit tests (own assert harness)
demo/loopback_demo.cpp mock radio<->phone exchange
CMakeLists.txt standalone build (lib + tests + demo)
# via CMake
cmake -B build . && cmake --build build && ctest --test-dir build --output-on-failure
# or directly, no CMake, no network
g++ -std=c++11 -Wall -Wextra -Iinclude src/protocol.cpp tests/test_protocol.cpp -o test && ./test
g++ -std=c++11 -Wall -Wextra -Iinclude src/protocol.cpp demo/loopback_demo.cpp -o demo && ./demo- Framing: HDLC-style SOF + byte-stuffing, CRC16-CCITT, streaming decoder with resync.
- Handshake:
HELLO/HELLO_ACKwith proto version + capability negotiation. - Messages: CHANNELS, TELEMETRY, LUA_DATA, KEY, TOUCH, CONFIG_READ/WRITE, AUDIO_EVENT, HEARTBEAT, ACK/NACK.
- Link state machine (
LinkManager):DETACHED → HANDSHAKING → ATTACHED, heartbeat timeout, and the central gating decisioncompanionInputAllowed()— the hard requirement that local nav buttons/scroll are inert unless a phone is attached (no ghost-scroll).
- The codec is pure logic; it never touches the flight-control path.
- Companion input (
KEY/TOUCH/CONFIG_WRITE) is gated onLINK_ATTACHED. - Corrupt / oversize / wrong-version frames are dropped, never half-applied.
- Loss of link →
DETACHED→ companion input disabled; the radio keeps executing its active model.
Note that CONFIG_WRITE can change model and radio settings, so it is consequential: the radio validates
and applies it, and it is gated on LINK_ATTACHED.
UE Protocol is the open link these projects speak — see ADOPTERS:
- edgetx-ue — EdgeTX fork with the companion overlay (prebuilt firmware for Pocket & QX7).
- UltraEdge app — the Android companion, on Google Play.
UE Protocol is open and will remain open source; the UltraEdge Android app is a separate, proprietary
client. File-level licence labels in this repository are currently being reconciled: the repository
LICENSE is Apache-2.0, CONTRIBUTING describes an Apache-2.0 reference codec with a
CC BY 4.0 specification, and protocol.h carries a GPL-3.0-or-later SPDX identifier. Check the file you
are using until this is settled.
UltraEdge is an independent project that builds on the EdgeTX community's work; it is not affiliated with or endorsed by EdgeTX.