This project transforms a vintage German transistor radio — the SABA Mainau — into a modern smart audio device powered by Raspberry Pi 4 and Raspberry Pi Pico. While preserving the iconic design and analog audio amplifier of the original, the project adds support for Spotify Connect, Internet Radio, and a TFT display interface, fully controlled by physical buttons and a rotary tuning dial.
Everything described below is the Raspberry Pi 4 version, the one covered in the YouTube series. It stays in this repository exactly as it was — the .NET service (RadioApp), the Angular admin UI (RadioFrontend) and the Pico firmware (RadioIO) are all still here and still build.
In practice, though, the SABA's mono transistor amplifier turned out to be a poor fit for a general-purpose media device. So the project has split. A proper media device is being built separately, and this radio is being simplified into what its cabinet is genuinely good at: a standalone internet radio driven by an ESP32.
What that means:
- The Raspberry Pi 4 is removed from the device, together with Spotify Connect, the web interface and the MyTuner scraper.
- An ESP32 (AZ-Delivery DevKit C V4) takes over, with a PCM5102A I2S DAC feeding the original SABA amplifier.
- The Raspberry Pi Pico I/O board and its firmware are unchanged — the same buttons, the same tuning dial, the same JSON messages over UART.
- The TFT display stays, rewired to the ESP32, with the same on-screen layout.
- With Spotify gone, all four toggle buttons (
L,M,K,U) select internet radio banks — 4 banks × 19 dial positions = 76 station slots, each with a stream URL, name and logo.
New work lives in Esp32InternetRadio/. The design and the reasoning behind it are in Architecture.md, and the step-by-step build order is in DeliveryPlan.md.
- Raspberry Pi 4 — main processing unit (audio, web interface, display)
- Raspberry Pi Pico — microcontroller for reading physical I/O (buttons, tuning dial)
- 1.77" TFT SPI Display (128x160, ST7735)
- Original SABA transistor amplifier — reused as final stage for audio output
- Remove original radio circuits, leaving only the transistor audio amplifier.
- Mix stereo output from Raspberry Pi’s 3.5mm jack into mono using two resistors. And inject this signal into radio's circuit.
- Mount TFT display to the front panel, connected to SPI interface of the Pi 4.
- Connect physical buttons to Raspberry Pi Pico.
- Use the original variable capacitor (from radio oscillator) as a tuning dial:
- Read its analog value via RC circuit and ADC input on the Pico.
- Connect Pico and Pi 4 via UART: Pico acts as an I/O controller, sending input events to the Pi.
The device will support two modes, switchable via physical controls:
-
Spotify Connect Mode
- Acts as a Spotify Connect device via Raspotify.
- Use physical button for Play/Pause.
- Use tuning dial to skip to Next/Previous Track.
- TFT screen shows track info and album art via Spotify API.
-
Internet Radio Mode
- Streams MP3 radio stations via VLC.
- Use physical controls to Play/Pause and switch stations.
- TFT screen displays station name and status.
- OS: Raspberry Pi OS Lite
- Audio:
- Spotify:
Raspotify(daemon) - Radio:
libVLC(called via .NET)
- Spotify:
- Main Application:
.NET 9 WebAPIhosted on Raspberry Pi 4- BackgroundWorker for input handling and mode management
- SQLite database to store:
- Radio stream URLs
- Spotify authorization tokens
- GPIO/SPI/UART: Accessed via
PIGPIOC library + .NET interop (P/Invoke) - Frontend UI:
- Web interface built with Angular
- Used for initial setup and Spotify authentication
- Hosted together with WebAPI app, accessible in local network via NGINX
| Component | Interface | Role |
|---|---|---|
| Raspberry Pi 4 | UART | Master, receives input events |
| Raspberry Pi Pico | UART + ADC | I/O controller (buttons, dial) |
| Pi 4 ↔ TFT LCD | SPI | Display track/station info |
All schematics, wiring diagrams, and specifications are in the Docs/ folder:
- Raspberry Pi Setup instructions
- System Architecture
- TFT Display And PICO Wiring
- Pico I/O & RC Tuning Circuit
- SABA Upgrade Circuit Plan
Diagrams are stored in Docs/Img/ and created using draw.io.
| Folder | Description |
|---|---|
| RadioApp | .NET WebAPI and main worker service project (Raspberry Pi 4 version) |
| RadioFrontend | Angular "admin" application for Spotify authentication and setup radio channels (Raspberry Pi 4 version) |
| RadioIO | C firmware for Raspberry Pi Pico — used by both versions |
| Esp32InternetRadio | PlatformIO firmware for the new ESP32 version |
| Docs | Markdown documentation & diagrams |