DECT NR+ live camera link

Live video from a camera module to a PC over a DECT NR+ radio link built from two nRF9151 development kits.

┌────────────────┐  UART 1 Mbaud  ┌──────────────┐   DECT NR+    ┌──────────────┐  VCOM1 1 Mbaud ┌─────────┐
│ ESP32-S3 + cam │ ─────────────► │ nRF9151 DK   │ ────────────► │ nRF9151 DK   │ ─────────────► │ PC      │
│ JPEG frames    │  framed frags  │ transmitter  │   1.9 GHz     │ receiver     │  framed frags  │ viewer  │
└────────────────┘                └──────────────┘               └──────────────┘                └─────────┘

The sensor produces JPEG, the camera board chops each frame into fragments sized to exactly one DECT transport block, and both radio boards move those fragments without ever looking inside them. All image handling lives at the two ends, which keeps the radio firmware small and lets every hop be tested on its own.

Measured

End to end at QVGA, JPEG quality 6, boards about 30 cm apart:

291 frames, 0 lost, 14.6 fps, 41.1 kB/s
291/291 decoded, 0 packet CRC errors
RSSI -33 dBm, SNR 24 dB, 0 radio errors

Resolution and quality are changeable at runtime. See docs/results.md for the full measurements, the resolution ladder, and the traps met along the way.

Repository layout

Path	What
nrf/	Transmitter and receiver firmware — Zephyr / nRF Connect SDK
esp32/	Camera firmware — ESP-IDF
viewer/	Reassembly and live display — Python + OpenCV
docs/	Architecture, wire protocol, wiring, measurements

The wire format is specified in docs/protocol.md. nrf/common/dectcam_proto.h is the reference implementation; it is copied verbatim into esp32/main/ and mirrored in Python as viewer/dectcam_viewer/proto.py, and a self-test checks the copies against one another.

Hardware

Radio	2 × nRF9151 DK, with DECT NR+ modem firmware installed
Camera	ESP32-S3 board with an OV2640 or OV3660 sensor and PSRAM
Wiring	4 jumper wires plus ground, 2 series resistors

Developed on a Freenove ESP32-S3 WROOM CAM, which is pin-compatible with Espressif's ESP32-S3-EYE. Any ESP32-S3 camera board works if you adjust the pin map in esp32/main/cam.c.

DECT NR+ operation needs the DECT PHY modem firmware on the nRF9151, which is distributed separately by Nordic Semiconductor and is not part of this repository.

See docs/wiring.md before connecting anything — in particular the two series resistors and the I/O rail voltage.

Getting started

Each part builds with its own vendor toolchain; there is no top-level build.

# 1. radio firmware  (needs nRF Connect SDK)
cd nrf
west build -b nrf9151dk/nrf9151/ns -d build/tx tx
west build -b nrf9151dk/nrf9151/ns -d build/rx rx
west flash -d build/tx --dev-id <transmitter-serial>
west flash -d build/rx --dev-id <receiver-serial>

# 2. camera firmware  (needs ESP-IDF)
cd ../esp32
idf.py set-target esp32s3
idf.py build
idf.py -p /dev/ttyUSB0 flash

# 3. viewer  (needs Python 3.10+)
cd ../viewer
python3 -m venv .venv
./.venv/bin/pip install -r requirements.txt
./run_viewer.sh

Full instructions, including how to tell the two DKs apart and what to check when nothing appears, are in each subdirectory's README.

Runtime control

Everything adjustable is reachable from the PC, through a side panel next to the picture:

cd viewer && ./run_panel.sh

Radio	Camera
Carrier (1657–1677, odd)	Resolution
MCS	Target frame rate
Transmit power index	JPEG quality

Commands travel against the video — PC → receiver → over the air → transmitter — and the transmitter either applies them to its radio or passes them to the camera. It announces its settings once a second, so the panel shows where the link actually is rather than what was last asked for.

Changing the carrier moves both ends. Neither waits for the other: each retunes on its own timer and returns to the previous channel by itself if no traffic appears, so a command that only half arrives cannot strand them apart.

The same commands are available without the GUI:

scripts/send_ctrl.py carrier 1667
scripts/send_ctrl.py res hvga
scripts/read_state.py

and the transmitter's own shell still works for the camera:

dectcam-tx:~$ cam quality 4
dectcam-tx:~$ dectstat

Regulatory note

Streaming video is a near-continuous transmit duty cycle. This firmware does not implement the channel-access rules of ETSI EN 301 406-2; a listen-before-talk gate is available as a build option but is not a substitute for compliance work. This is lab equipment, and it is the operator's responsibility to confirm what is permitted locally before transmitting.

Licence

Apache-2.0. See LICENSE.