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CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

What This Project Is

PcMeter is a Windows system tray application that reads CPU and memory utilization and sends the data over serial to an Arduino-based physical meter device (analog gauges with LEDs). There is also Arduino firmware for the device itself.

Projects

There are two Windows tray applications in this repo. The modern one (PcMeter/) supersedes the legacy one (PcMeter (legacy)/).

PcMeter — .NET 10 WPF (current)

dotnet build PcMeter/PcMeter.csproj
dotnet run --project PcMeter/PcMeter.csproj

Architecture — PcMeter (.NET 10 WPF)

Entry point is App.xaml.cs (App : Application). There is no main window; the app is tray-only with ShutdownMode = OnExplicitShutdown.

App.xaml.cs — central orchestrator. Owns the single-instance Mutex, creates the three services and TrayMenu, and wires up event handlers. Runs a 500ms DispatcherTimer that reads metrics and sends serial data each tick. All menu click handlers are private OnXxxMenuClick() methods here. App.xaml is minimal — no resources or XAML-defined UI.

Navigation/TrayMenu — encapsulates the TaskbarIcon and ContextMenu. Builds the menu items (CPU%, memory%, Connect, Settings, About, Exit) in CreateTrayIcon(), exposes events (ConnectClicked, SettingsClicked, AboutClicked, ExitClicked), and provides UpdateCpuMem(), RefreshMenuState(), and ShowNotification() methods. Implements IDisposable.

Services/

  • AppSettings — POCO with ComPort property. Load() / Save() read and write %APPDATA%\PcMeter\settings.json via System.Text.Json. Default port is COM20.
  • MetricsService — CPU% via PerformanceCounter("Processor", "% Processor Time", "_Total"); Memory% via P/Invoke through PsApiWrapper. Formula: 100 - (available / total * 100). Implements IDisposable.
  • SerialService — wraps SerialPort at 9600 baud. Connect() / Disconnect() / TrySend(cpu, mem). Fires ErrorOccurred(message) for unexpected errors and ConnectionLost for silent mid-session drops (unplug, sleep/resume); both events are marshaled to the UI thread via the captured Dispatcher. The timer in App.xaml.cs auto-reconnects each tick when disconnected, and polls SerialPort.GetPortNames() after each send to catch silent unplugs (USB drivers buffer writes, so no exception is thrown on device removal).
  • PsApiWrapper — static helper; P/Invokes psapi.dll!GetPerformanceInfo and returns (available, total) page counts.

Views/SettingsWindow — lists available COM ports in a ComboBox, pre-selects the saved port, and calls _settings.Save() on OK.

Views/AboutWindow — shows app info, MIT license text, and a clickable URL opened via Process.Start with UseShellExecute = true.

NuGet packages: H.NotifyIcon.Wpf (tray icon), System.IO.Ports (serial), System.Diagnostics.PerformanceCounter (CPU stats).

Serial Protocol

The Windows app sends to the Arduino:

  • C{0-100}\r — CPU percentage
  • M{0-100}\r — memory percentage

Messages are sent together every 500ms: C{cpu}\rM{mem}\r

Arduino firmware (arduino/pcmeter.ino) — runs on an Arduino Leonardo at 9600 baud. Smooths values using a rolling average of 20 readings, drives two analog meters via PWM, and controls green/red LEDs (red zone ≥80%). Includes a screensaver mode when no serial data is received for 2 seconds.