Use a Benshi-compatible Bluetooth radio (Vero VR-N76, VR-N7600, and similar) as the transceiver for SvxLink.

This is a Linux port of the radio layer from BenshiNode. It connects to the radio's Bluetooth Classic control and audio services, speaks the Gaia control protocol, exchanges SBC audio, and exposes the radio to SvxLink through SvxLink's native NetTrx / RemoteTrx protocol.

The result is a normal SvxLink simplex node or repeater with the Benshi radio as its RF front end. SvxLink still provides DTMF command handling, parrot, identification, EchoLink, Reflector, AllStar, and the other modules you configure.

Benshi radio  <-- Bluetooth RFCOMM (Gaia + SBC) -->  svxlink-benshi
                                                             |
                                            TCP NetTrx (2.8) |
                                                             v
                                                       svxlink

See INSTALL.md for the complete step-by-step installation.

SvxLink modules loaded with MODULES= are voice-service plugins. They sit in the audio chain of an already existing transceiver; they cannot be the transceiver and cannot inject receiver audio into the logic core. A radio backend has to implement SvxLink's Rx/Tx side.

SvxLink already has a supported mechanism for that: its RemoteTrx protocol, used by remotetrx and the built-in NetRx/NetTx transceiver types. This project implements the server side of that protocol, so SvxLink sees a normal network transceiver. No SvxLink source changes, custom .so plugin, ALSA loopback (snd-aloop), or PTY/GPIO PTT wiring is required.

• Bluetooth Classic RFCOMM control and audio channels (BlueZ)
• SDP discovery of the SPP control service and the vendor "BS AOC" audio service, with a generic-audio fallback
• Gaia device status, notifications, channel/VFO configuration, APRS setting
• SBC encode/decode compatible with the radio (32 kHz, mono, 16 blocks, 8 subbands)
• 32 kHz radio audio <-> SvxLink audio resampling (8000, 16000, or 32000 Hz)
• Radio squelch, VOX squelch, or automatic combination
• RX and TX gain controls
• DTMF decoding from radio audio, with tone muting, forwarded to SvxLink
• SVXLink NetTrx protocol version 2.8 with optional HMAC-SHA1 authentication
• RAW (float32) and S16 audio codecs
• Automatic Bluetooth reconnect
• Diagnostic commands: --probe, --dump, --unkey, --test-tx, --list

• Linux with BlueZ
• A paired and trusted Benshi-compatible radio
• SvxLink with NetTrx protocol 2.8 (SvxLink 1.10.x / current master)
• Build dependencies: CMake, a C++17 compiler, pkg-config, BlueZ development headers, OpenSSL development headers

# 1. Build and install the bridge
cmake -S . -B build \
  -DCMAKE_INSTALL_PREFIX=/usr \
  -DCMAKE_INSTALL_SYSCONFDIR=/etc
cmake --build build -j
ctest --test-dir build --output-on-failure
sudo cmake --install build

# 2. Pair and trust the radio (see INSTALL.md for bond troubleshooting)
svxlink-benshi --list
bluetoothctl
#   scan on
#   pair AA:BB:CC:DD:EE:FF
#   trust AA:BB:CC:DD:EE:FF

# 3. Edit the bridge config
sudo editor /etc/svxlink-benshi.conf
#   MAC=AA:BB:CC:DD:EE:FF
#   SAMPLE_RATE=16000

# 4. Install/configure SvxLink, then run the bridge and SvxLink
svxlink-benshi --config /etc/svxlink-benshi.conf
# in another terminal:
svxlink --config=/etc/svxlink/svxlink.conf

Full details, including how to build SvxLink and install the sound pack, are in INSTALL.md.

The example bridge configuration is config/svxlink-benshi.conf. The key settings are:

[RADIO]
MAC=AA:BB:CC:DD:EE:FF
DUAL_WATCH=0
APRS=0
TX_LEAD_MS=100

[SVXLINK]
BIND=127.0.0.1
PORT=5210
AUTH_KEY=
SAMPLE_RATE=16000

The matching SvxLink sections are in config/svxlink.conf.example:

[SimplexLogic]
TYPE=Simplex
RX=RxBenshi
TX=TxBenshi
MODULES=ModuleHelp,ModuleParrot
CALLSIGN=MYCALL

[RxBenshi]
TYPE=Net
HOST=127.0.0.1
TCP_PORT=5210
CODEC=S16
AUTH_KEY=

[TxBenshi]
TYPE=Net
HOST=127.0.0.1
TCP_PORT=5210
CODEC=S16
AUTH_KEY=

SAMPLE_RATE must match the INTERNAL_SAMPLE_RATE that SvxLink was compiled with. Current SvxLink defaults to 16000; older builds and some distribution packages use 8000. 32000 also works.

If BIND is not loopback, set a non-empty AUTH_KEY in [SVXLINK] and in both SvxLink transceiver sections. NetTrx traffic is not encrypted; use a VPN or SSH tunnel for remote links.

Once the bridge and SvxLink are running, key the radio and use DTMF:

If Help is active, 1# is interpreted by Help as "show module 1". Send just # to leave Help first, or wait for the module timeout.

# List nearby Bluetooth devices
svxlink-benshi --list

# Connect, print radio status/device info, disconnect
svxlink-benshi --probe

# Print memory channels and radio settings
svxlink-benshi --dump

# Force the radio out of transmit
svxlink-benshi --unkey

# Transmit a 1 kHz test tone for two seconds (RF on air!)
svxlink-benshi --test-tx

Both programs log to the terminal. To keep logs while running in the background:

svxlink-benshi --config /etc/svxlink-benshi.conf 2>&1 | tee benshi.log
svxlink --config=/etc/svxlink/svxlink.conf 2>&1 | tee svxlink.log

• RX: SBC frames from the radio are decoded to 32 kHz mono PCM. Gain and squelch are applied, then audio is downsampled to SvxLink's internal rate and sent as S16 or RAW NetTrx audio.
• TX: audio from SvxLink is upsampled to 32 kHz, encoded to SBC, and written to the radio in batches. Sending audio keys the radio; the end frame unkeys it.
• A short lead silence (TX_LEAD_MS) lets the radio's playout buffer settle. While keyed, silence is sent between network chunks so brief scheduling hiccups do not sound like dropouts.
• DTMF is decoded from the radio's 32 kHz audio and forwarded to SvxLink as NetTrx MsgDtmf messages. The tones are muted from the forwarded audio.

br-connection-key-missing or AuthenticationFailed
The Bluetooth bond is stale. Delete the computer/host pairing on the radio, then re-pair from Linux:

sudo btmgmt bondable on
bluetoothctl remove AA:BB:CC:DD:EE:FF
bluetoothctl --timeout 10 scan on
bluetoothctl pair AA:BB:CC:DD:EE:FF
bluetoothctl trust AA:BB:CC:DD:EE:FF
bluetoothctl connect AA:BB:CC:DD:EE:FF

No matching RFCOMM service found
Pair and trust the radio, power it on, and confirm with bluetoothctl info <MAC>. Some firmware needs a moment after pairing before SDP is available.

Radio connects but there is no RX audio
Run --probe and check squelch/RSSI. Try SQUELCH_MODE=vox and adjust VOX_THRESHOLD_DB. Check the radio volume and channel.

Audio sounds choppy
Keep the default TX_LEAD_MS=100. Check system load and Bluetooth link quality. Make sure only one program is controlling the radio. Do not run SvxLink's remotetrx on the same port (5210).

SvxLink says Could not find audio clip ...
The English sound pack is not installed. See INSTALL.md.

SvxLink heartbeat timeout
Both Rx and Tx must use the same HOST/TCP_PORT so SvxLink shares one NetTrx connection. Keep the bridge running.

• Linux only. The radio transport uses BlueZ RFCOMM; BenshiNode remains the Windows implementation.
• One NetTrx client at a time, matching SvxLink's remotetrx server behavior.
• Radio audio is resampled with simple filters optimized for voice.
• SVXLink tone detectors requested with MsgAddToneDetector are ignored. DTMF works, but 1750 Hz tone-burst repeater opening and CTCSS/PL detection are not implemented; use DTMF or squelch-based opening instead.
• Configure CTCSS on the radio or with [RADIO] RX_CTCSS/TX_CTCSS in the bridge, not with SvxLink's TX_CTCSS/CTCSS settings.
• SVXLink's MsgSendDtmf request (used by the DTMF repeater module) is ignored.
• The bridge does not bridge BenshiNode's proprietary link/reflector protocol. It makes the radio a transceiver for SvxLink instead.

• Radio protocol, SBC framing, and the original Windows implementation: BenshiNode.
• NetTrx protocol and SvxLink: Copyright Tobias Blomberg / SM0SVX, SvxLink, GPL-2.0-or-later.
• SBC codec: Google libsbc, Apache-2.0, see third_party/sbc/LICENSE.

This project is licensed under GPL-2.0-or-later; see LICENSE.