zyphlar
78 lines
3.5 KiB
Markdown
78 lines
3.5 KiB
Markdown
# BabyMobile Audio Manager (PWA)
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A dependency-free, **client-side** web app that scans for the BabyMobile XIAO
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(nRF52840) over Bluetooth LE and manages the audio files on it. No backend, no
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build step, nothing leaves your device — all audio conversion happens in the
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browser with the Web Audio API.
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Pairs with the firmware in `../baby_mobile_v2/baby_mobile_v2.ino`.
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## What it does
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- **Scan & connect** to the `BabyMobile` BLE peripheral.
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- **Convert** any browser-decodable file (WAV/MP3/M4A/OGG/FLAC…) to a conformant
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mono PCM WAV — **8-bit / 8 kHz by default**, with 8/16-bit and 8/16/32 kHz
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selectable. The full WAV (44-byte header + data) is streamed intact; the
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firmware self-configures bit depth and sample rate from the header.
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- **Upload** to any of the 32 track slots, with a live progress bar driven by the
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device's status-notification byte count.
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- **Play / stop** any slot.
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- **Remember** what you uploaded per browser (localStorage), since the firmware
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exposes no track-listing command over BLE.
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## BLE protocol used
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| | UUID | Use |
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|---|---|---|
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| Service | `12340001-…` | advertised |
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| Cmd (write) | `12340002-…` | `0x02 <slot>` start upload · `0x03` finish · `0x04 <slot>` play · `0x05` stop · `0x06` list · `0x07 <slot>` delete |
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| Data (write-without-response) | `12340003-…` | raw WAV bytes, chunked to 180 B |
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| 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 |
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## Running it
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Web Bluetooth requires a **secure context**: `https://` or `http://localhost`.
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```sh
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# from this app/ directory — any static server works
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python -m http.server 8000
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# then open http://localhost:8000
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```
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Deploy the folder as-is to any static host (GitHub Pages, Netlify, Cloudflare
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Pages…) to install it as a PWA from a phone. It's a complete app shell with a
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service worker, so it also launches offline once cached.
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## Platform support
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| Platform | BLE works? | How |
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| Android | ✅ | Chrome or Edge; "Add to Home screen" installs the PWA |
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| Windows / macOS / Linux | ✅ | Chrome or Edge |
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| **iPhone / iPad** | ⚠️ via Bluefy | iOS Safari/WebKit has **no** Web Bluetooth |
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### iOS setup (no App Store)
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Apple doesn't ship Web Bluetooth, so a plain Safari PWA can't reach BLE. Use the
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free **[Bluefy – Web BLE Browser](https://apps.apple.com/app/bluefy-web-ble-browser/id1492822055)**:
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open this app's URL inside Bluefy and everything works. (Bluefy itself is the
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only App Store install needed — the app stays a web app.)
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If you later want a true installable iOS app without Bluefy, wrap this same
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folder in [Capacitor](https://capacitorjs.com/) with `@capacitor-community/bluetooth-le`
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and reuse `ble.js`'s protocol constants.
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## Notes & limits
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- **Flash size:** the firmware's POC stores tracks in the nRF52840's internal
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LittleFS, which is small. 8-bit/8 kHz ≈ 8 KB per second of audio — keep clips
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short. If the device acknowledges fewer bytes than sent, the app warns you
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(flash likely full).
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- **Listing & delete are live:** on connect (and after every upload/delete) the
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app sends `0x06` to read the device's real track table, and `0x07` deletes a
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slot on the device. Track *titles* aren't stored on the device, so they're
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remembered locally and shown next to the live entries; an uploaded slot with no
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local name just shows "Track N".
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- **MTU:** data is chunked to 180 bytes to stay within a modest negotiated ATT
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MTU (firmware char max is 240).
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