# BabyMobile Audio Manager (PWA)

A dependency-free, **client-side** web app that scans for the BabyMobile XIAO
(nRF52840) over Bluetooth LE and manages the audio files on it. No backend, no
build step, nothing leaves your device — all audio conversion happens in the
browser with the Web Audio API.

Pairs with the firmware in `../baby_mobile_v2/baby_mobile_v2.ino`.

## What it does

- **Scan & connect** to the `BabyMobile` BLE peripheral.
- **Convert** any browser-decodable file (WAV/MP3/M4A/OGG/FLAC…) to a conformant
  mono PCM WAV — **8-bit / 8 kHz by default**, with 8/16-bit and 8/16/32 kHz
  selectable. The full WAV (44-byte header + data) is streamed intact; the
  firmware self-configures bit depth and sample rate from the header.
- **Upload** to any of the 32 track slots, with a live progress bar driven by the
  device's status-notification byte count.
- **Play / stop** any slot.
- **Remember** what you uploaded per browser (localStorage), since the firmware
  exposes no track-listing command over BLE.

## BLE protocol used

| | UUID | Use |
|---|---|---|
| Service | `12340001-…` | advertised |
| Cmd (write) | `12340002-…` | `0x02 <slot>` start upload · `0x03` finish · `0x04 <slot>` play · `0x05` stop · `0x06` list · `0x07 <slot>` delete |
| Data (write-without-response) | `12340003-…` | raw WAV bytes, chunked to 180 B |
| Status (notify) | `12340004-…` | tagged by byte 0: `0x00…` upload byte count (uint32 BE) · `0x80\|idx, bits, kHz, secs` list entry · `0xFF, n` list end · `0xD0, idx, ok` delete reply |

## Running it

Web Bluetooth requires a **secure context**: `https://` or `http://localhost`.

```sh
# from this app/ directory — any static server works
python -m http.server 8000
#   then open  http://localhost:8000
```

Deploy the folder as-is to any static host (GitHub Pages, Netlify, Cloudflare
Pages…) to install it as a PWA from a phone. It's a complete app shell with a
service worker, so it also launches offline once cached.

## Platform support

| Platform | BLE works? | How |
|---|---|---|
| Android | ✅ | Chrome or Edge; "Add to Home screen" installs the PWA |
| Windows / macOS / Linux | ✅ | Chrome or Edge |
| **iPhone / iPad** | ⚠️ via Bluefy | iOS Safari/WebKit has **no** Web Bluetooth |

### iOS setup (no App Store)

Apple doesn't ship Web Bluetooth, so a plain Safari PWA can't reach BLE. Use the
free **[Bluefy – Web BLE Browser](https://apps.apple.com/app/bluefy-web-ble-browser/id1492822055)**:
open this app's URL inside Bluefy and everything works. (Bluefy itself is the
only App Store install needed — the app stays a web app.)

If you later want a true installable iOS app without Bluefy, wrap this same
folder in [Capacitor](https://capacitorjs.com/) with `@capacitor-community/bluetooth-le`
and reuse `ble.js`'s protocol constants.

## Notes & limits

- **Flash size:** the firmware's POC stores tracks in the nRF52840's internal
  LittleFS, which is small. 8-bit/8 kHz ≈ 8 KB per second of audio — keep clips
  short. If the device acknowledges fewer bytes than sent, the app warns you
  (flash likely full).
- **Listing & delete are live:** on connect (and after every upload/delete) the
  app sends `0x06` to read the device's real track table, and `0x07` deletes a
  slot on the device. Track *titles* aren't stored on the device, so they're
  remembered locally and shown next to the live entries; an uploaded slot with no
  local name just shows "Track N".
- **MTU:** data is chunked to 180 bytes to stay within a modest negotiated ATT
  MTU (firmware char max is 240).