PROJECT: CC-CC to OpenBridge Translator

NOTICE: CC-CC is not a published, open protocol. Support for it here is derived from interoperability analysis against a production c-Bridge, not from vendor documentation (see CC-CC_Link_Protocol_Specification.md). Several details remain undefined or assumed (see that document's §13); please do not ask for features that require further reverse-engineering without providing verified, legally obtained information about the protocol.

PURPOSE: A single, small native daemon that bridges c-Bridge CC-CC links to OpenBridge peers — HBlink3, HBlink4, or any other product that speaks OpenBridge. cc2obp is the server-tier counterpart to ipsc2hbpc: where ipsc2hbpc bridges one IPSC repeater system to one HomeBrew network, cc2obp bridges any number of CC-CC links to any number of OpenBridge peers, one CC-CC link to exactly one OpenBridge (system, TGID) at a time.

WHAT IT DOES:

Each configured [[link]] pairs one CC-CC conduit (a Control Center's Bridge Group, reached over TCP 42421 + UDP 42422/42420) with one OpenBridge (peer, TGID) pair, always on DMR slot 1 (the OpenBridge convention). A call originating on either side — CC-CC B-on/voice/B-off, or an OpenBridge DMRD VOICE_HEAD/burst/VOICE_TERM — is translated in real time and relayed to the other side, with no playout timer, jitter buffer, or loss concealment: packets are translated and forwarded on arrival, and gaps present as real gaps on the far end, not synthesized filler.

DESIGN GOALS:

• Transparent translation only. No routing, bridging, talkgroup rewriting, or DMR-ID lookups. Group voice in, group voice out, unchanged.
• Single event loop, single thread. A poll()-based loop multiplexes every CC-CC and OpenBridge socket and all timers. No threads, no locks.
• Any number of links, any number of peers. One shared CC-CC listener and voice/keepalive socket serve every configured [[link]]; one UDP socket per enabled [[openbridge]] peer. Strictly 1:1:1 — a CC-CC link and an OpenBridge (system, TGID) never fan out to more than each other. If you need N-way conference bridging spanning CC-CC, compose it by pointing an HBlink3 bridge.py confbridge at one of cc2obp's OpenBridge legs, rather than expecting cc2obp itself to do fan-out.
• One TOML config file. See CONFIGURING.md.
• No external dependencies. The TOML parser, HMAC-SHA1, the event loop, and the DMR DSP/FEC code are all in this repository and compiled into the binary — no Python, no pip, no third-party libraries.
• enabled / cross_connect_active runtime toggles, reloadable via SIGHUP without a full restart — for taking a link out of service, or for transit-side maintenance that keeps the far Control Center from seeing reconnect churn while you work behind the OpenBridge leg.

ARCHITECTURE:

• dmr/ — self-contained DMR DSP/FEC library (BPTC(196,96), embedded LC, AMBE 49↔72-bit conversion, RS(12,9), Hamming, Golay), shared with ipsc2hbpc and validated bit-for-bit against the reference dmr_utils3 implementation.
• cccc/ — the CC-CC side: link state machine (handshake, keepalive, link-test reflector, B-on/B-off), and the CC-CC 21-byte voice payload ⇄ AMBE bit-packing.
• openbridge/ — the OpenBridge side: per-peer UDP socket, HMAC-SHA1 framing, DMRD send/receive.
• translate.c — wires the two sides together: the link table, per-call state, and both directional translation flows.
• tests/ — a DSP self-test against golden vectors, a CC-CC AMBE bit-packing test, and two system tests that drive the compiled binary over real loopback sockets (SSRC collision; orphaned call and sequence/timestamp gap consistency).

VERIFICATION:

make test

runs all four suites — 117 checks as of this writing, 0 failures.

WHAT IT IS NOT:

This is not a general-purpose bridge, reflector, or conference server. It does not do N-way bridging, talkgroup rewriting, or DMR-ID lookups. It speaks CC-CC on one side and OpenBridge on the other, and only ever translates one call at a time per configured link.

REQUIREMENTS:

• A C11 compiler and make
• A CC-CC-speaking remote (a c-Bridge Control Center) to link to
• An OpenBridge-speaking peer to link to — HBlink3, HBlink4, or another OpenBridge-capable product

GETTING STARTED:

make
cp cc2obp.toml.sample cc2obp.toml
# edit cc2obp.toml — see CONFIGURING.md
./cc2obp -c cc2obp.toml --log-level DEBUG

See INSTALL.md for the systemd service, and CONFIGURING.md for how to fill in a working config, including what you'll need from the operator of the far end of each link.

PROPERTY:

This work represents the author's interpretation of the CC-CC and OpenBridge protocols. CC-CC behavior is derived from interoperability analysis against a production c-Bridge (see CC-CC_Link_Protocol_Specification.md); OpenBridge behavior is derived from HBlink3. The DMR DSP/FEC code is shared with ipsc2hbpc, itself a C port of dmr_utils3 (N0MJS, with original AMBE work by Mike Zingman N4IRR and FEC routines after Jonathan Naylor G4KLX).

No Support Is Provided

This is not commercial software. It is provided free of charge. The author(s) received no compensation for creating and maintaining it. Countless hours over many years have gone into the this. If you have problems, the author will try to help if possible, please have no expectations for support. There is no online group, such as DVSwitch or groups.io that is an "official" outlet for information. The only definitive source of information is me. Beware of others claiming to be authoritative. User-based mutual support is great, and I'm all for it. But please understand, this is what they are, and I have not sanctioned anyone to be the "home" of my software packages.

GitHub "Issues"

Do not use GitHub issues for support. Genuine bugs are accepted as issues. Before opening one, make sure that it is a true problem with the software and not merely a misconfiguration, or contention around a feature that was not supported. Isssues should never be used to ask for or recommend features. Issues that do not include complete details, relevent tracebacks, error messages, configuration snippets, operatrional conditions surrounding the event, etc. will be closed without action.

0x49 DE N0MJS

Copyright (C) 2026 Cortney T. Buffington, N0MJS n0mjs@me.com

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA