# DigiRadio ### DAB+/FM Bluetooth Receiver with SigmaDSP Audio Processing **Open-source digital radio — Si4684 tuner · ADAU1701 SigmaDSP · Bluetooth aptX Adaptive · ESP32-S3** ![Status](https://img.shields.io/badge/hardware-verified-brightgreen) ![Firmware](https://img.shields.io/badge/firmware-in%20development-orange) ![PCB](https://img.shields.io/badge/PCB-6--layer-blue) ![Hardware License](https://img.shields.io/badge/hardware-CERN--OHL--S-lightgrey) ![Firmware License](https://img.shields.io/badge/firmware-MIT-lightgrey)
--- ## Overview **DigiRadio** is an open-source digital radio receiver that combines terrestrial broadcast reception (**DAB+ / DAB / FM**) with a programmable audio-processing stage and high-quality **Bluetooth** audio output. Incoming broadcast audio is decoded by a Silicon Labs **Si4684** digital-radio receiver, processed by an Analog Devices **ADAU1701 SigmaDSP** (equalisation, mixing, level control), and transmitted over Bluetooth by a Qualcomm QCC3056-based **Feasycom FSC-BT1035** module supporting the **aptX Adaptive** codec. An Espressif **ESP32-S3** acts as the host controller, orchestrating the three subsystems and providing Wi-Fi/BLE connectivity and a USB service interface. The entire tuner → DSP → Bluetooth path is **fully digital (I²S, 48 kHz / 24-bit)** — no analogue conversions are introduced between the tuner and the wireless link. ``` FM/DAB antenna → [ Si4684 ] --I²S--> [ ADAU1701 DSP ] --I²S--> [ FSC-BT1035 ] → aptX ↑ ↑ ↑ └──── SPI ──── [ ESP32-S3 host ] ──── UART ────┘ │ I²C ``` --- ## Key Features - **DAB+ / DAB / FM** reception (Si4684) via external whip antenna (SMA) - **Fully digital audio path** — no avoidable A/D–D/A conversions - **Programmable audio processing** on the ADAU1701 SigmaDSP - **Bluetooth 5.2** output with **aptX / aptX HD / aptX Adaptive** - **ESP32-S3** host with native USB, Wi-Fi and BLE - **USB-C powered**; single-rail 3.3 V + low-noise 1.8 V for the tuner - **6-layer impedance-controlled PCB**, 50 × 90 mm, two ground planes - Three antennas (ESP32 2.4 GHz, BT1035 2.4 GHz, FM/DAB SMA) with proper keep-outs --- ## Repository Structure ``` DigiRadio/ ├── docs/ Technical Reference Manual (LaTeX source + PDF) │ └── DigiRadio_Manual.pdf ├── Hardware/ │ ├── schematics/ Schematic (PDF) │ ├── gerber/ Gerber + drill files (fabrication) │ ├── bom/ Bill of Materials │ ├── pick-and-place/ Component placement (CPL / centroid) │ ├── easyeda/ EasyEDA source project │ └── 3d/ 3D renders / STEP └── Software/ Firmware (in development — see Software/README.md) ``` --- ## Documentation The full design is described in the **[Technical Reference Manual](docs/DigiRadio_Manual.pdf)**, covering the system architecture, signal chain, clock and power design, the 6-layer stack-up and controlled-impedance strategy, the functional blocks, and the design decisions behind the key choices. --- ## Design Highlights | Topic | Choice | Rationale | |---|---|---| | **Audio quality** | QCC3056 / aptX Adaptive | The codec is the dominant quality factor on a wireless link; the DAC lives in the sink | | **Audio path** | Fully digital I²S | Avoids unnecessary A/D–D/A conversions between tuner and Bluetooth | | **I²S master** | ADAU1701 (12.288 MHz) | Clean ×256 → 48 kHz; avoids sample-rate mismatch | | **Stack-up** | 6-layer, 2× GND | Solid ground reference under RF, crystals and USB | | **USB routing** | TOP, ref. GND | 90 Ω diff achievable at manufacturable geometry | | **Antennas** | 3 zones, diagonal 2.4 GHz | Coexistence separation + full-layer keep-outs | --- ## Status - ✅ **Schematic** — complete and reviewed - ✅ **PCB layout** — 6-layer, DRC clean, plane continuity verified - ✅ **BOM** — finalised (manufacturable / sourced) - 🔜 **Prototype** — in fabrication (PCBWay) - 🛠️ **Firmware** — in active development (released after bring-up) --- ## Manufacturing The board is manufactured with **PCBWay** as a 6-layer, impedance-controlled PCB with turnkey assembly. The FSC-BT1035 Bluetooth module is sourced from Feasycom (the footprint uses a BT806-compatible, pin-identical land pattern). See the [Manufacturing chapter](docs/DigiRadio_Manual.pdf) of the manual for fabrication notes, impedance-control settings and MSL-3 handling of the BT module. --- ## License - **Hardware** (schematic, PCB, Gerber): [CERN-OHL-S](https://ohwr.org/cern_ohl_s_v2.txt) - **Firmware / software**: [MIT](https://opensource.org/licenses/MIT) - **Documentation**: CC BY 4.0 Intellectual property of the design remains with the author. You are free to study, modify and build the hardware under the terms of the respective licenses. --- ## Author **Michele Bigi** — Open-source hardware project. *Contributions, issues and questions are welcome via the repository issue tracker.*