nad2go

REST API server for controlling NAD amplifiers and receivers via RS232 serial port. Written in Go with zero external HTTP dependencies. Connects to the amplifier through a USB-to-serial adapter and exposes simple HTTP endpoints that can be called from Home Assistant, scripts, or any HTTP client.

Currently includes IR command mappings for the NAD C725BEE, but the RS232 protocol is shared across many NAD models — adapt the IR map for your unit.

Features

• Full RS232 control — power, source, mute, speakers, tuner, sleep, tone defeat, and more
• IR command passthrough — send any remote control command via Main.IR using plain-text names (e.g. volume_up) or decimal codes
• Auto-reconnect — recovers gracefully if the serial connection drops
• Home Assistant ready — simple GET endpoints work directly with rest_command

Requirements

• NAD amplifier/receiver with RS232 serial port
• USB-to-serial adapter (e.g. PL2303-based cable)
• Go 1.23+ (for building from source)

Configuration

Env Variable	Default	Description
SERIAL_PORT	/dev/cu.PL2303G-USBtoUART2140	Serial port path
PORT	8080	HTTP listen port

Endpoints

GET /control

Send a command to the amplifier.

Param	Required	Description
cmd	yes	RS232 command: Main.Power, Main.IR, Main.Source, Main.Model…
op	yes	Operator: = (set), + (increment), - (decrement), ? (query)
value	no	Value to set. For Main.IR, accepts plain-text names like volume_up

Response:

{"command": "Main.Power=On", "response": "Main.Power=On"}

GET /status

Returns serial port connection status.

{"portPath": "/dev/cu.PL2303G-USBtoUART2140", "connected": true}

GET /ir-commands

Returns the full IR command name-to-decimal-code mapping as JSON. Useful for discovering available commands.

RS232 Protocol

NAD RS232 commands follow the format \r<Command>\r (carriage return before and after).

Command	Values	Description
Main.Power	On / Off	Power on/off
Main.Source	1–6	Input source
Main.Mute	On / Off	Mute
Main.SpeakerA	On / Off	Speaker A output
Main.SpeakerB	On / Off	Speaker B output
Main.Dimmer	On / Off	Display dimmer
Main.Sleep	0–90	Sleep timer (minutes)
Main.ToneDefeat	On / Off	Tone defeat
Main.Model	(query)	Model number
Main.Version	(query)	Firmware version
Main.IR	decimal code	Send IR remote command

Note: Volume is not available as a direct RS232 command. Use Main.IR with volume_up (136) or volume_down (140).

Usage Examples

# Query model number
curl "http://localhost:8080/control?cmd=Main.Model&op=?"

# Power on
curl "http://localhost:8080/control?cmd=Main.Power&op==&value=On"

# Volume up
curl "http://localhost:8080/control?cmd=Main.IR&op==&value=volume_up"

# Volume down
curl "http://localhost:8080/control?cmd=Main.IR&op==&value=volume_down"

# Speaker A on via IR
curl "http://localhost:8080/control?cmd=Main.IR&op==&value=speaker_a"

# Mute
curl "http://localhost:8080/control?cmd=Main.Mute&op==&value=On"

# Change source to input 3
curl "http://localhost:8080/control?cmd=Main.Source&op==&value=3"

# Increment source
curl "http://localhost:8080/control?cmd=Main.Source&op=+"

# Query FM frequency
curl "http://localhost:8080/control?cmd=Tuner.FM.Frequency&op=?"

# Use decimal IR code directly
curl "http://localhost:8080/control?cmd=Main.IR&op==&value=206"

# List available IR commands
curl "http://localhost:8080/ir-commands"

Home Assistant

rest_command configuration

rest_command:
  nad_power_on:
    url: "http://nad2go:8080/control?cmd=Main.Power&op==&value=On"
  nad_power_off:
    url: "http://nad2go:8080/control?cmd=Main.Power&op==&value=Off"
  nad_volume_up:
    url: "http://nad2go:8080/control?cmd=Main.IR&op==&value=volume_up"
  nad_volume_down:
    url: "http://nad2go:8080/control?cmd=Main.IR&op==&value=volume_down"
  nad_mute:
    url: "http://nad2go:8080/control?cmd=Main.Mute&op==&value=On"
  nad_unmute:
    url: "http://nad2go:8080/control?cmd=Main.Mute&op==&value=Off"
  nad_source:
    url: "http://nad2go:8080/control?cmd=Main.Source&op==&value={{ source }}"

Automation example

automation:
  - alias: "Turn on amplifier when TV starts"
    trigger:
      - platform: state
        entity_id: media_player.living_room_tv
        to: "playing"
    action:
      - service: rest_command.nad_power_on
      - delay: "00:00:02"
      - service: rest_command.nad_source
        data:
          source: "1"

Run

Direct

SERIAL_PORT=/dev/cu.PL2303G-USBtoUART2140 go run .

Build and run

go build -o nad2go .
SERIAL_PORT=/dev/cu.PL2303G-USBtoUART2140 ./nad2go

Docker

docker compose up --build

The docker-compose.yml maps the serial device into the container. Edit the devices section to match your adapter path.

Project Structure

File	Description
server.go	HTTP server, endpoints, main entrypoint
serial.go	Serial port communication, auto-reconnect
irmap.go	IR command name → decimal code mapping
Dockerfile	Multi-stage alpine build
docker-compose.yml	Container config with serial passthrough

License

MIT