GUI Overview

pcu ships as two programs: the desktop app (pcu / pcu.exe) documented in this section, and the command-line companion pcu-cli covered in the Command Reference. The app looks and works the same on Windows and Linux.

Launching pcu

On Windows:

1. Run pcu.exe.
2. pcu needs Administrator rights to reach the hardware, so it relaunches itself elevated and Windows shows a UAC prompt. Accept it.

If you decline the prompt, or start the app without Administrator rights some other way, the splash screen shows “Administrator privileges required” and tells you to right-click pcu.exe and select “Run as administrator”.

On Linux:

• Launch pcu from the desktop entry that the installer adds, or run pcu from a terminal. No root is needed once you are in the i2c group (see Install on Linux).

On both platforms:

• Only one copy of pcu runs at a time. Starting a second copy shows “pcu is already running.” and exits.
• A splash screen appears while pcu connects to the hardware. It stays up for at least two seconds and then the main window opens. If pcu cannot reach the hardware, the main window still opens and the sidebar shows the reason, with a “Retry” button. The splash itself only shows an error when pcu is not running as Administrator (see above) or startup fails outright.

The window

The main window is titled “pcu - Platform Control Utility”. A sidebar on the left holds the connection status and the page navigation; the selected page fills the rest of the window.

Once pcu is connected, a green “Connected” indicator at the top of the sidebar names the platform. If the connection fails, an error box appears there instead, with a “Retry” button (and, on Windows when the PawnIO driver is missing, a “Driver Setup” button).

Under the “NAVIGATION” heading are seven pages:

Page	What it is	Available
Home	Welcome and status	Always
Ignition	Timer configuration	Platforms with ignition timers (CQ20)
Digital I/O	Inputs and outputs	Platforms with digital I/O (CQ40)
Driver	Hardware access setup	Windows only
Platforms	Supported hardware	Always
CLI Commands	Command reference	Always
About	Info and licenses	Always

A page that does not apply to the connected hardware is greyed out. Hover it to see why: before pcu connects, the tooltip reads “Connect to the hardware to use this option.”; once connected to hardware that lacks the feature, it reads “This option isn’t available on this platform or pcu version.”

The Home page

Home opens first and is available on any platform. It shows:

• System Status. On Windows, a “PawnIO Driver” row shows “Installed”, “Not installed”, or “Reboot required”, with an “Install Driver” button when the driver is missing. On Linux, a “Kernel I2C Transport” row shows an “i2c-dev” badge instead, because there is no driver to install. A “Hardware Connection” row shows “Connected” or “Disconnected”; when connected it lists the platform description and MCU identity, and when not it reads “Not connected to MCU hardware.”
• Live status overview. Once connected, Home shows a live status dashboard that refreshes every 5 seconds while the page is open.
• Quick Navigation. Shortcut buttons to the pages your platform supports.
• Getting Started. When pcu is not yet connected, a numbered checklist: set up hardware access (install the PawnIO driver on Windows, or join the i2c group on Linux), run on supported hardware, then configure.

The other pages

• Ignition configures the power-sequence timers. See Ignition Page.
• Digital I/O monitors inputs and switches outputs. See Digital I/O Page.
• Driver manages the Windows kernel driver. See Driver Page.
• Platforms compares the supported hardware. Full detail on Supported Platforms.
• CLI Commands is an in-app copy of the pcu-cli command reference. It is generated from the same catalogue as pcu-cli’s own help, so the two cannot drift apart. Full version: Command Reference.
• About shows the version, build details, transports, and licenses.

If the connection drops

pcu checks the hardware link every 5 seconds. If it is lost, the sidebar shows “Connection to MCU hardware was lost.” and its live data stops. Use “Retry” (or “Driver Setup” on Windows) to reconnect; a successful reconnect returns you to Home. See Connection and Detection if it keeps happening.