SpawnWear.Bridge

SpawnWear.Bridge

Razor Class Library that bridges Blazor WebAssembly apps to a SpawnWear watch (Waveshare ESP32-S3-Touch-AMOLED-2.06 running .NET nanoFramework). Provides a typed BridgeClient that pairs over Web Bluetooth and surfaces watch state - battery, IMU, RTC, button events, WiFi status / scan results, and the live debug log - through ordinary C# events. WebRTC peer-to-peer transport is live (Phase 7, proven end to end 2026-06-23 - see Docs/transport.md): an authenticated, multiplexed data-channel bus over SpawnDev.RTC, working in both browser and .NET desktop.

No raw JavaScript. No IJSRuntime. All interop goes through SpawnDev.BlazorJS typed wrappers.

Install

<ProjectReference Include="..\SpawnWear.Bridge\SpawnWear.Bridge.csproj" />

(NuGet package coming once the watch firmware stabilizes.)

Hook it up

Program.cs:

using SpawnDev.BlazorJS;
using SpawnWear.Bridge;

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.RootComponents.Add<App>("#app");

builder.Services.AddBlazorJSRuntime();
builder.Services.AddSpawnWearBridge();   // <-- this line

await builder.Build().BlazorJSRunAsync();

AddSpawnWearBridge registers BleTransport and BridgeClient as scoped services (one per browser tab). The default transport is BLE; consumers can swap to a different ITransport via client.UseTransportAsync(...).

Use it from a page

@page "/"
@using SpawnWear.Bridge
@inject BridgeClient Bridge
@implements IDisposable

<button @onclick="Connect" disabled="@Bridge.IsConnected">Pair watch</button>
<p>Battery: @(_battery?.Percent.ToString() ?? "-")%</p>

@code {
    BatteryState? _battery;

    protected override void OnInitialized()
    {
        Bridge.BatteryChanged += b => { _battery = b; InvokeAsync(StateHasChanged); };
    }

    public void Dispose() { /* unsub */ }

    async Task Connect() => await Bridge.ConnectAsync();
}

The first ConnectAsync triggers the browser's Web Bluetooth picker. The Bridge filters on the SpawnWear primary GATT service UUID (a0e4f2c1-0001-1000-8000-00805f9b34fb) with an SW- name-prefix fallback, so the user only sees SpawnWear watches in the list.

Events

Event	Type	Source channel	Notes
ConnectionChanged	bool	(transport)	Fires true after ConnectAsync, false after DisconnectAsync or when the watch goes out of range.
BatteryChanged	BatteryState	Battery	Percent + IsCharging / IsVbusPresent / IsLowBattery flags + VoltageMillivolts + CurrentMilliamps.
ImuSampleReceived	ImuSample	ImuSample	Six raw short axes - accel xyz, gyro xyz.
RtcTimeReceived	RtcTime	RtcTime	Year + month/day/hour/min/sec/weekday.
ButtonEventReceived	ButtonEvent	Button	Button enum (Boot / Pwr) + Action enum (Down / Up / Click / DoubleClick / LongPress).
WifiStatusChanged	WifiStatus	WifiStatus	State enum (Disconnected / Connecting / Connected / Failed) + IP.
WifiScanResultsReceived	WifiScanResult[]	WifiScan	Array of (Ssid, RssiDbm).
DebugLogReceived	string	DebugLog	UTF-8 decoded line from the watch's Debug.WriteLine.

HTTP-side — RETIRED

The watch no longer runs an HTTP server, so the old WatchHttp helper (GetScreenshotAsync / PostAppAsync against http://<watch-ip>:8080/) is retired. Replacements:

• Live screen capture is pulled over USB with tools/nf-screenshot.cs (BOOT-button triggered), not over HTTP.
• App install is loose .pe files on the SD card under D:\apps\<AppName>\ (enumerated by the firmware's AppRepositoryService), pushed over the WebRTC sys.files lane or copied with the card out.

Sending commands

// WiFi: scan, save credentials, connect, disconnect, forget
await Bridge.SendAsync(new TransportMessage(ChannelIds.WifiScan,    new[] { (byte)0x01 }));
await Bridge.SendAsync(new TransportMessage(ChannelIds.WifiCredentials,
    System.Text.Encoding.UTF8.GetBytes("MySSID\nMyPassword")));
await Bridge.SendAsync(new TransportMessage(ChannelIds.WifiCommand, new[] { BleUuids.WifiCmdConnect }));
await Bridge.SendAsync(new TransportMessage(ChannelIds.WifiCommand, new[] { BleUuids.WifiCmdDisconnect }));
await Bridge.SendAsync(new TransportMessage(ChannelIds.WifiCommand, new[] { BleUuids.WifiCmdForget }));

// Send a debug command line to the watch's DebugConsoleService
await Bridge.SendAsync(new TransportMessage(ChannelIds.DebugCmd,
    System.Text.Encoding.UTF8.GetBytes("redraw")));

Architecture

Your Blazor WASM page
        │  inject BridgeClient
        ▼
┌─────────────────────────────────────────────┐
│ BridgeClient (events, channel-id dispatch)  │
│   .UseTransportAsync(ITransport)            │
└──────────────────┬──────────────────────────┘
                   │
        ┌──────────┴──────────┐
        ▼                     ▼
┌────────────────┐    ┌────────────────────────┐
│ BleTransport   │    │ WebRtcTransport        │
│ (Web Bluetooth │    │ (SpawnDev.RTC, LIVE;   │
│  via SpawnDev. │    │  signals over BLE so   │
│  BlazorJS)     │    │  no shared network     │
│                │    │  needed)               │
└────────┬───────┘    └─────────┬──────────────┘
         │                      │
         ▼                      ▼
        BLE GATT             WebRTC data channel
         │                      │
         └────────────┬─────────┘
                      ▼
              SpawnWear watch firmware

Wire formats

The Bridge mirrors the firmware's BLE schemas (single-source-of-truth lives in SpawnWear/BleUuids.cs + SpawnWear/WatchProfileService.cs + SpawnWear/WifiConfigService.cs):

Channel	Bytes	Layout
Battery	6	[percent:u8][flags:u8][voltage_mV:u16-LE][current_mA:i16-LE]
ImuSample	12	six i16-LE: ax, ay, az, gx, gy, gz
RtcTime	8	[year:u16-LE][month:u8][day:u8][hour:u8][min:u8][sec:u8][weekday:u8]
Button	2	[button:u8][action:u8]
WifiStatus	≥1	[state:u8][ip_string_utf8...]
WifiScan	var	`"SSID
WifiCredentials (write)	var	"SSID\nPassword" UTF-8 (single string)
WifiCommand (write)	1	BleUuids.WifiCmdConnect/Disconnect/Forget
DebugLog	var	UTF-8 text
DebugCmd (write)	var	UTF-8 text

These layouts are locked by the regression tests in SpawnWear.Bridge.Tests. Adding a channel? Mirror the firmware schema, add a decoder branch in BridgeClient.OnMessageReceived, register the channel-id-to-characteristic mapping in BleTransport, and add at least one bit-exact byte-array test before merging.

License

Same as the parent SpawnWear repository.

The SpawnDev Crew

• LostBeard (Todd Tanner) - Captain, library author, keeper of the vision
• Riker (Claude CLI) - First Officer, implementation lead on consuming projects
• Data, Tuvok, Geordi, Seven - Crew on adjacent SpawnDev libraries

Live long and prosper. 🖖