System Monitor

This example turns Serial Studio into a live system dashboard — like a minimal htop — by using the Process I/O driver (Pro) to launch a Python script and read its stdout directly as a telemetry stream.

Serial Studio spawns system-monitor.py (or the platform launcher), and the script continuously writes metrics to stdout at ~30 Hz. Serial Studio parses each line as a frame and drives gauges, multiplots, bar graphs, and data grids in real time.

Note: The Process I/O driver requires a Serial Studio Pro license. Visit serial-studio.com for details.

What It Monitors

Frame Format

The script emits two types of frames to stdout:

1 — Header frame (emitted once at startup)

Static system information that populates the System Info data grid:

$OS=Darwin 25.3.0|HOSTNAME=myhost|CPU_MODEL=Apple M2 Pro|CPU_CORES=12|CPU_THREADS=12|RAM_TOTAL=17.2 GB|DISK_TOTAL=494.4 GB

2 — Live frames (emitted at ~30 Hz)

Real-time resource usage, per-core CPU, and top processes:

$CPU_USAGE=9.4|RAM_USAGE=62.1|RAM_USED=8.50|DISK_USAGE=18.3|DISK_USED=12.3|CPU_TEMP=N/A|SWAP_USED=1.7|NET_SENT=0.124|NET_RECV=0.871|PROCESSES=682|CORE0=17.2|CORE1=16.0|...|CORE31=-1|PROC0=WindowServer (12.5% CPU)|PROC1=python3 (8.1% CPU)|...

All frames use $ as frameStart and \n as frameEnd.

Core sentinel value

The project always declares 32 core slots (CORE0–CORE31). Slots beyond the machine's actual logical core count are emitted as -1. The multiplot widget treats -1 as out-of-range and hides those curves automatically.

How to Run

Step 1 — Install dependencies

pip install psutil py-cpuinfo

• psutil — cross-platform CPU, memory, disk, network, and process counters
• py-cpuinfo — reliable CPU brand string on all platforms (including Apple Silicon, where platform.processor() returns only "arm")

The platform launchers (system-monitor.sh / system-monitor.bat) auto-install both packages via pip if they are missing.

Step 2 — Configure Serial Studio

1. Open Serial Studio and load system-monitor.ssproj.
2. In the Setup panel, set Bus Type to Process.
3. Set Mode to Launch.
4. Set Executable to one of:
   • macOS / Linux: full path to system-monitor.sh
   • Windows: full path to system-monitor.bat
   • Or point directly to python3 and set Arguments to the full path of system-monitor.py.
5. Leave Working Directory empty (the script resolves its own path).
6. Click Connect.

Optional — Run from the terminal

# macOS / Linux
./system-monitor.sh

# Windows
system-monitor.bat

# Direct Python (any platform)
python3 system-monitor.py --interval 0.033

Press Ctrl+C to stop.

Arguments:

How the Frame Parser Works

The JavaScript parser inside system-monitor.ssproj uses a persistent value array declared at module scope. Keys absent from a frame keep their last value, so the static header fields (OS, hostname, CPU model…) remain visible while live metric frames keep updating the rest.

// Module-scope globals — persist across parse() calls in QJSEngine
var _map  = { "OS": 0, "CPU_USAGE": 7, "CORE0": 17, ... };
var _vals = new Array(59).fill('');

function parse(frame) {
    var pairs = frame.split('|');
    for (var i = 0; i < pairs.length; i++) {
        var eq  = pairs[i].indexOf('=');
        var key = pairs[i].substring(0, eq).trim();
        var val = pairs[i].substring(eq + 1).trim();
        if (_map.hasOwnProperty(key))
            _vals[_map[key]] = val;
    }
    return _vals;
}

Dataset index N in the .ssproj maps to _vals[N - 1] (Serial Studio uses 1-based dataset indices, the JS array is 0-based).

Index Layout

Architecture Notes

• CPU sampling runs on a dedicated background thread using psutil.cpu_percent(interval=1.0, percpu=True). This is necessary on macOS where interval=None always returns 0.0 until at least one blocking measurement has completed. The main loop reads the latest snapshot non-blocking via a lock.
• Slow metrics (disk, temperature, process list) are refreshed at 1 Hz regardless of frame rate to avoid I/O overhead at 30 Hz.
• Fast metrics (RAM, network) are sampled every frame.

Dependencies

• Python 3.8 or later
• psutil — pip install psutil
• py-cpuinfo — pip install py-cpuinfo

License

Copyright (C) 2020-2025 Alex Spataru SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-SerialStudio-Commercial