Denon Controller

A web remote for a Denon AVR-4308CI receiver, running on a Raspberry Pi. It controls power, volume, mute and input source for the main zone and zones 2 and 3, from any browser on the home network (phone included).

The receiver can be reached over RS-232 (a USB-to-serial adapter on the Pi) or the network (telnet, TCP port 23). The choice is one setting; nothing else changes.

 Phone / browser ──► Denon.Web.Remote ──► Denon.Web.Api ──► Denon.Core.Command ──► receiver
   (page + JS)        port 5090            port 5091         serial or TCP

Projects

Project	What it is
Denon.Web.Api	ASP.NET Core Web API. Translates REST calls into receiver commands using the device schema in Schemas/4308ci.json.
Denon.Web.Remote	ASP.NET Core MVC web page: volume dials, power and mute switches, source dropdown per zone. Calls the API from the browser.
Denon.Core.Command (folder Denon.Core.Telnet)	Connections to the receiver: TcpConnection (network) and SerialConnection (RS-232), plus the shared reply reader.
Denon.Core.Model	Shared models: device schema, configuration, command responses.
Denon.Telnet.Test	Command-line tool: send commands to the receiver over the network and print the replies.
Denon.Serial.Test	Command-line tool: send commands to the receiver over the serial port. See its README.

Docs/ holds notes on undocumented commands and the receiver's UPnP service descriptions. The command set comes from Denon's AVR-4308CI control protocol, version 5.1.0a (PDF on Denon's site; not included here).

How it behaves

• One command at a time. The connection stays open between commands and is reopened automatically if the receiver drops it.
• Unsolicited status lines are ignored. The receiver announces changes made from its front panel or remote; those lines are filtered out of command replies.
• Fails fast when the receiver is off or unplugged. The API answers 503 Receiver ... not reachable within about 2 seconds, then immediately for the next 5 seconds, so requests don't pile up.
• Volume limit. The API never sets a volume above Safety:MaxVolume, and the page's dials stop there.
• Cross-site protection. Only the pages listed in Security:AllowedOrigins can call the API from a browser.

Configuration

The committed settings files use example addresses (192.168.1.100, raspberrypi.local). Put your own in a appsettings.{Environment}.Local.json file next to them, e.g. appsettings.Production.Local.json on the Pi and appsettings.Development.Local.json for debugging. Git ignores these files; they are read after appsettings.{Environment}.json, and publishing copies them with the app. Only the values that differ are needed:

{
  "DeviceConfig": { "Host": "192.168.1.50" },
  "Security": { "AllowedOrigins": [ "http://my-pi.home.lan:5090", "http://192.168.1.20:5090" ] }
}

A list such as AllowedOrigins is merged by position, so the local file's list should be at least as long as the one it replaces.

API — Denon.Web.Api/appsettings.json

"DeviceConfig": {
  "ModelFilename": "4308ci.json",       // device schema in Schemas/
  "ConnectionType": "Serial",           // "Serial" or "Telnet"
  "Host": "192.168.x.x",                // receiver address (Telnet)
  "TelnetPort": 23,
  "Serial": {
    "PortName": "/dev/ttyUSB0",         // COMx on Windows; /dev/serial/by-id/... is stable across reboots
    "BaudRate": 9600, "DataBits": 8, "Parity": "None", "StopBits": "One"
  },
  "TimeoutRatio": "1",                  // multiplies every command's reply timeout
  "TelnetConnectionTimeout": 300000     // close an idle network connection after this many ms
},
"Safety": {
  "MaxVolume": 80,                      // 80 = 0 dB reference, 98 = receiver maximum
  "MaxVolumeByZone": { }                // optional per zone, e.g. { "2": 70 }
},
"Security": {
  "AllowedOrigins": [ "http://<pi-name>:5090" ],   // every address the remote page is opened from
  "EnableRawCommandEndpoint": false     // SendCommand bypasses all checks; debugging only
},
"Kestrel": { "Endpoints": { "Http": { "Url": "http://0.0.0.0:5091" } } }

Web remote — Denon.Web.Remote/appsettings.json

"DeviceConfig": {
  "RemoteWebApi": "http://<pi-name>:5091/api/Remote/",   // used by the browser, so not "localhost"
  "TimeoutRatio": "1",
  "RemoteWebApiTimeoutSeconds": 5       // optional; server-side call to the API when the page loads
},
"Kestrel": { "Endpoints": { "Http": { "Url": "http://0.0.0.0:5090" } } }

Device schema — Denon.Web.Api/Schemas/4308ci.json

Defines the receiver's commands and how to read their replies, plus:

• configuration.zones — zone IDs (M, 2, 3) and the names shown on the page.
• configuration.sources — the input sources:

  { "id": "CD", "default": "CD", "name": "Raspotify", "enabled": true }

  id is the receiver's code (sent as SICD, Z2CD, ...), name is an optional custom label (empty = use default), and enabled controls whether the page offers it. The API always returns every source.

Editing the schema only needs an API restart, not a rebuild.

API endpoints

All GET, under /api/Remote/. Swagger UI is at /swagger on the API.

Area	Endpoints
Setup	GetConfiguration (zones, sources, volume limits, receiver model, API version), CheckConnectionStatus, GetSystemModel
Power	GetSystemPowerStatus, SetSystemPowerOn, SetSystemPowerStandBy, GetZonePowerStatus, SetZonePowerOn, SetZonePowerOff
Volume	GetMasterVolume, SetMasterVolume?value=, SetMasterVolumeUp/Down, SetZoneVolume?zoneId=&value=, SetZoneVolumeUp/Down
Mute	GetMasterVolumeMute, SetMasterVolumeMute?value=ON|OFF, ...On/Off, and the Zone equivalents with zoneId
Source	GetSourceList, GetSourceListDefault, GetMasterSource, SetMasterSource?source=, GetZoneSource, SetZoneSource

Volume is 00–98 (half steps as 455 = 45.5 on the main zone) or UP/DOWN. Invalid values get 400; an unreachable receiver gets 503.

Development

• Open Denon Controller.sln in Visual Studio and start both Denon.Web.Api and Denon.Web.Remote.
• appsettings.Development.json listens on all interfaces, so the remote can be tried from a phone at http://<dev-pc-ip>:5000. Allow ports 5000 and 5091 through the Windows firewall.
• Only one program can use the receiver's connection: stop the services on the Pi (or the test tools) while debugging against the same receiver.

Deploying to the Raspberry Pi

1. Publish both projects with the linux-arm64 profile (self-contained; the Pi doesn't need .NET installed).
   • API: Denon.Web.Api/bin/Release/linux-arm64
   • Remote: Denon.Web.Remote/bin/Release/net10.0/linux-arm64
2. Stop both services on the Pi, copy each publish folder over, and start them again. If copied from Windows: chmod +x Denon.Web.Api Denon.Web.Remote.
3. For serial: the account running the API needs the port — sudo usermod -aG dialout <user> (then log in again).
4. Check: the API log shows Receiver connection: serial port ..., GET /api/Remote/CheckConnectionStatus returns "systemState":"Alive", and the page footer shows the receiver model and matching versions.

Versioning

Directory.Build.props sets one version for all projects (currently 1.1.0); bump it when deploying. The SDK appends the git commit, and the remote's footer shows both services' versions — AVR-4308USA | Remote 1.1.0+1c9df25 | API 1.1.0+1c9df25 — so a mismatch means one service wasn't redeployed.

Test tools

# Network (telnet)
dotnet Denon.Telnet.Test.dll -a <receiver-ip>              # interactive; Up/Down for command history
dotnet Denon.Telnet.Test.dll -a <receiver-ip> -c "MV?" -q  # one command, raw reply only

# Serial
dotnet Denon.Serial.Test.dll -n /dev/ttyUSB0

Both keep the last 100 commands in ~/.denon.telnet.test_history / ~/.denon.serial.test_history.

License

GNU General Public License v3.0. See LICENSE.