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Daily Operation

HALPI2 is designed for unattended operation. On the preinstalled HaLOS image — or any operating system with the HALPI daemon installed — power management is automatic: the device charges its backup super-capacitors, rides out voltage glitches, shuts the operating system down safely when power is lost, and starts up again when power returns. None of this requires user action.

Powering On

HALPI2 has no power button on the enclosure: it starts whenever input power is connected. (An external power button can be wired to the carrier board — see External Buttons.) The LED bar first fills up with red while the super-capacitors charge (seconds to half a minute, depending on the current limit setting). The LEDs then play a short rainbow and color-cycle animation while the compute module starts, show a yellow bar while the operating system boots, and turn green once the operating system is running and the HALPI daemon has connected.

Shutting Down

To shut down HALPI2, cut the input power — for example with a switch on the electrical panel. The system detects the power loss, shuts the operating system down gracefully on super-capacitor power, and stays off. The LEDs show a purple bar while the shutdown runs and turn off when it completes.

You can also shut down through software — the desktop menu, the shutdown command, or halpi shutdown. The system then powers off and stays off until the input power is cycled (or an external power button, if fitted, is pressed).

Optionally, the controller can restart the system automatically about 5 seconds after a software shutdown while input power remains connected, so that an accidental shutdown command never strands an installation that is hard to reach physically. Enable it with halpi config set auto_restart true; the setting persists in the controller. Units produced before early 2026 shipped with this behavior enabled — check yours with halpi config get auto_restart.

The system can also be put into standby, where it powers off and wakes up again at a scheduled time — see the Carrier Board Controller reference.

Status LED Indicators

The five front-panel LEDs show what the system is doing:

LED pattern Meaning
Red bar filling up Super-capacitors charging before startup — wait
Rainbow and cycling colors Compute module starting up. If the pattern repeats without progress, the module failed to start — see Troubleshooting
Yellow bar Running, HALPI daemon not connected — normal for a short time during boot. If it persists, see Troubleshooting
Green bar Normal operation
Orange or dark green bar Input power lost, running on backup — shutdown follows unless power returns within seconds
Purple bar Shutting down
All solid red Operating system unresponsive — the controller will restart it automatically
All flashing red Super-capacitor fault — contact support
All solid blue Entering standby
All dim red Standby
All off Powered off

In the bar patterns, the number of lit LEDs shows the super-capacitor charge level. The exact voltage windows and the full state mapping are in the Carrier Board Controller reference.

The LED brightness can be adjusted — see LED Control. The LEDs can also be repurposed as a display for system metrics and marine data (network activity, tank levels, NMEA 2000 and Signal K values) with the HALPI2 blinkenlights add-on.

When Power Is Lost

Nothing needs to be done. Brief dips and glitches — up to 5 seconds by default — are bridged by the super-capacitors, and operation continues undisturbed. In a longer outage, the system shuts itself down gracefully on the 30–60 seconds of backup power the super-capacitors hold. When input power returns, the system starts up again automatically.

Not a UPS

The super-capacitors exist to bridge glitches and to power a safe shutdown. For continued operation through extended outages, an external uninterruptible power supply is required.

Checking System Health

A green LED bar means the system is healthy. For details, the halpi command shows the controller state, voltages, current, and temperatures:

halpi status

If something looks wrong, see Troubleshooting and the Software Guide.

Running Without the Daemon

On operating systems without the HALPI daemon, the controller falls back to a basic protection mode: it still detects power loss and requests a shutdown, but by simulating power-button presses — which fails if the system is frozen — and monitoring and configuration are unavailable. If you run a custom operating system, install the daemon; see Other Debian Distributions. How the two modes work is described in the Carrier Board Controller reference.

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