Thursday, March 05, 2026

This Blog Has Moved to prolinix.com

This blog has a new home.

After several years on Blogspot, I have moved all my content to a self-hosted site:

prolinix.com

What changed?

  • All existing posts from this blog have been migrated to prolinix.com
  • New posts will only be published on the new site
  • This Blogspot site will stay online as an archive but will not be updated

Why the move?

I wanted more control over how the site looks and works. The new site is built with Hugo and hosted on Cloudflare Pages with features like dark mode, image galleries, search, comments, and an RSS feed.

Stay in touch

Thanks to everyone who read and followed this blog over the years. See you on the new site!

Wednesday, February 18, 2026

Build a Low-Cost DIY USB Volume Knob with Digispark ATtiny85

This project turns a cheap Digispark ATtiny85 USB dongle and a KY-040 rotary encoder into a dedicated hardware volume knob. Rotate clockwise for volume up, counter-clockwise for volume down, press to mute. It enumerates as a standard USB HID Consumer Control device — no custom driver, no desktop app. Linux, Windows, and many Android devices recognise it out of the box.

Last updated: February 19, 2026

3D render of the DIY USB volume knob showing a Digispark ATtiny85 board connected to a KY-040 rotary encoder

3D render of the assembled volume knob — Digispark ATtiny85 USB board with KY-040 rotary encoder.

Finished DIY USB volume knob plugged into a USB port, showing the Digispark board with rotary encoder attached

The finished USB volume knob — plug in and it works immediately as a standard HID device.

Why Build This?

Keyboard shortcuts work, but a physical knob is better when you are:

  • Switching between headphones and speakers
  • On a call and need instant mute
  • Using a media PC or mini server with no easy keyboard access
  • Tired of digging into software mixer panels

For around 5–10 USD in parts you get a dedicated hardware control that is always there.

Parts

Parts required for the DIY USB volume knob: Digispark ATtiny85 board, KY-040 rotary encoder, and jumper wires

Everything needed: Digispark ATtiny85 USB board, KY-040 rotary encoder module, and jumper wires.

  • Digispark ATtiny85 USB board — ~2 USD
  • KY-040 rotary encoder module — ~1 USD
  • Jumper wires (female-to-female) — ~1 USD
  • Optional: 3D-printed case or aftermarket knob for a cleaner finish

Wiring

Wiring diagram showing connections between KY-040 rotary encoder and Digispark ATtiny85 board

Connection diagram: KY-040 rotary encoder wired to the Digispark ATtiny85 USB board.

Rotary Encoder Digispark ATtiny85
CLK P5 (PB5)
DT P2 (PB2)
SW P0 (PB0)
+ 5V
GND GND

ATtiny85 pin mapping used by this project:

                 +-\/-+
ENC_A (CLK) PB5  1|    |8  Vcc
USB D-      PB3  2|    |7  PB2  ENC_B (DT)
USB D+      PB4  3|    |6  PB1
            GND  4|    |5  PB0  ENC_SW (SW)
                 +----+

Note: PB5 is used as GPIO for encoder input in this design (RSTDISBL fuse context applies when programming bare chips). Digispark boards typically ship in a suitable configuration already.

Assembly

The build is straightforward — solder the five wires between the encoder module and the Digispark board as shown in the wiring table above, then attach a knob cap. The numbered steps below show the full process from bare parts to finished device:

Step-by-step assembly of the DIY USB volume knob: 12 numbered photos showing progression from bare Digispark board and rotary encoder to finished USB device with knob cap

Assembly steps 1–12: from bare components to a finished USB volume knob ready to plug in.

Firmware

The firmware sends standard HID Consumer Control usages:

HID Usage Function
0xE9 Volume Increment
0xEA Volume Decrement
0xE2 Mute

Because these are standard HID usages, the host OS handles them natively — no custom driver needed.

Build and Flash

Clone the repository and build the firmware and uploader:

git clone https://github.com/hackboxguy/attiny85-hid-rotary-knob.git
cd attiny85-hid-rotary-knob
make all

This builds main.hex (firmware) and tools/micronucleus/micronucleus (uploader).

Flash via Micronucleus bootloader:

make upload

Tip: After running make upload, you will see "Waiting for device...". Plug in the Digispark within 60 seconds — the upload starts automatically once the bootloader is detected.

If your setup does not require sudo:

make upload SUDO=''

Note: Digispark boards come with the Micronucleus bootloader pre-installed — just plug in and upload. This blog assumes a board with a working bootloader. If you have a blank ATtiny85 chip without Micronucleus, flashing the bootloader requires an ISP programmer and is outside the scope of this guide.

Build prerequisites: Install gcc-avr, avr-libc, binutils-avr, libusb-1.0-0-dev, and pkg-config before running make.

Platform Compatibility

Linux

Works out of the box as a USB HID media control device. Desktop environments map it immediately to system volume and mute. Good fit for Ubuntu/Debian desktops, Arch with Wayland or X11, and Raspberry Pi media boxes.

Windows

Also works without drivers as a standard media-control device. If you briefly see "USB device not recognized" right after plugging in, that is the short Micronucleus bootloader window before the firmware enumerates. After handoff, the knob works normally.

Android

Works on Android devices that support USB OTG and HID media keys. You need a USB-C OTG adapter (or Micro-USB OTG on older phones) and OTG host support enabled on the device.

Android caveats: Behaviour can vary by OEM/ROM. Some devices only react when the screen is unlocked, and mute handling may differ across apps.

Troubleshooting

  • Build fails with missing AVR tools — Install the prerequisites listed in the Build and Flash section above.
  • Linux error -71 during USB enumeration — Reflash or repair the bootloader. See the repository troubleshooting section.
  • No response to rotation — Check CLK/DT wiring first (most common issue), then confirm the encoder module GND and 5V connections.

Going Further

The firmware is intentionally simple and stable, but the hardware supports extensions:

  • Multi-mode knob (volume / media transport / brightness)
  • Long-press and double-click actions
  • Mode indicator LED
  • Additional HID report descriptors

Start with a practical tool, then evolve it into a custom desktop controller.

Tuesday, February 17, 2026

VMBOX: Deliver Web Apps as Self-Contained Virtual Machines

VMBOX packages web applications and runtime dependencies into a self-contained VirtualBox VM. Teams can deliver internal tools as a portable OVA artifact with browser-first access, reducing per-app EXE/MSI/DEB installation work on managed endpoints.

Last updated: February 18, 2026

The Problem

If you've ever tried to deploy a custom tool on managed Windows laptops, you know the pain. Installing Python, setting up dependencies, dealing with Group Policy restrictions, getting IT approval for a new .msi — it all takes longer than writing the tool itself.

Container workflows can also solve packaging, but they often require Docker/Desktop approval, daemon operation, and additional endpoint permissions. In tightly managed enterprise environments, a VM artifact is often easier to deploy and support.

VMBOX takes a different approach. It wraps the full application stack — OS, runtime, dependencies, and web UI — into a single VirtualBox image. When VirtualBox is available, users can import an .ova, start the VM, and access the tool in a browser with predictable setup steps.

What is VMBOX?

VMBOX is a build system for generating minimal Alpine Linux-based VirtualBox images. Reference builds are lightweight (often around ~150MB compressed), boot quickly on modern hardware, and expose functionality through browser-accessible web interfaces without requiring a full desktop environment.

At its core, VMBOX provides:

  • Immutable root filesystem — SquashFS-based read-only rootfs with OverlayFS for runtime changes
  • Persistent data partition — Separate ext4 partition for user data and configurations
  • Optional APP partition — A dedicated read-only SquashFS partition for deploying custom web apps and services
  • Factory reset — One-click reset that restores the system to its original state without reimporting the OVA
  • System management dashboard — Built-in web UI for monitoring CPU, memory, disk, network, and managing applications
  • Cross-platform portability — Export as OVA for use on Windows, macOS, or Linux

System Architecture

VMBOX uses a multi-partition disk layout designed for reliability and easy updates:

VMBOX system architecture showing 4-partition layout: BOOT, ROOTFS, DATA, and APP partitions with OverlayFS merge

VMBOX disk layout: BOOT (FAT32) loads the kernel, ROOTFS (SquashFS) holds the immutable Alpine system, DATA (ext4) stores persistent state via OverlayFS, and APP (SquashFS) contains custom applications.

The BOOT partition contains the Syslinux bootloader, kernel, and initramfs. The ROOTFS partition is a read-only SquashFS image of Alpine Linux with all base services. The DATA partition provides persistent read-write storage — it holds the OverlayFS upper layer, user home directories, and application data. The optional APP partition is another read-only SquashFS image containing your custom web applications, mounted at /app.

During boot, the initramfs merges the read-only ROOTFS with the read-write DATA partition using OverlayFS. This means the system always has a clean base to fall back to — a factory reset simply wipes the overlay, and on the next reboot you're back to a pristine state.

App Delivery as a Single Artifact

The core idea behind VMBOX is that deploying a web application should not require each end user to install and maintain app-specific host runtimes. Compare a traditional rollout with VMBOX:

Traditional Deployment VMBOX Deployment
Install Python/Node runtime
Install dependencies
Configure environment
Deal with OS-specific issues
Navigate endpoint policy approvals
Write platform-specific installers
Import .ova file
Start VM
Open browser to localhost:8000
Done.

This works for any application that can be accessed through a browser: business dashboards, LLM-powered tools, internal APIs, operational utilities, and optional hardware-facing interfaces. Any web framework/runtime that fits your packaging flow can be delivered as a VMBOX image.

Compared with container-first distribution, VMBOX trades daemon/image orchestration for a portable VM artifact and browser-based access. The operating model is straightforward: import, start, and connect.

System Management Dashboard

Every VMBOX image ships with a built-in system management web UI at http://localhost:8000. After boot, sign in (reference builds use admin/brb0x) and change the password on first use. The dashboard provides real-time monitoring and control without requiring SSH for routine operations:

VMBOX System Management Dashboard showing CPU, memory, disk gauges, network stats, applications panel, and log viewer

The System Management Dashboard: real-time CPU, memory, and disk monitoring, application status, log viewer, and system actions — all accessible from the browser.

The dashboard uses Server-Sent Events for 1-second live updates and includes:

  • CPU / Memory / Disk gauges with visual progress bars
  • Network statistics — real-time RX/TX traffic
  • Applications panel — status and control of all apps from the APP partition
  • Log viewer — search, filter, clear, and download logs
  • System actions — change password, reboot, factory reset

Optional: USB Passthrough for Embedded/Hardware Workflows

For embedded and hardware teams, VMBOX can optionally enable VirtualBox USB passthrough with automatic device filters. This allows selected USB devices to be forwarded to the VM for serial, ADB, or CAN workflows when host policy permits:

  • FTDI FT232/FT2232 (VID 0403) — common serial adapters
  • Silicon Labs CP210x (VID 10C4) — USB-to-UART bridges
  • WCH CH340/CH341 (VID 1A86) — budget serial adapters
  • Prolific PL2303 (VID 067B) — serial adapters
  • PCAN-USB (VID 0C72) — CAN bus adapters (optional)
  • Arduino boards (VID 2341) — development boards

When passthrough is enabled, a compatible USB adapter can appear inside the VM within seconds. Combined with a web-based terminal or device UI packaged in APP, teams can access hardware workflows through the browser without installing per-tool UI apps on each host.

Note: USB 2.0/3.0 passthrough requires the VirtualBox Extension Pack; USB 1.1 works without it.

Remote Collaboration via VPN

VMBOX can be paired with an approved VPN or internal network path (for example WireGuard, Tailscale, or enterprise VPN) to enable remote collaboration. Once the VM is reachable, colleagues can access web-based tools through a browser without local app installation.

This supports distributed teams and shared lab resources: one engineer can host the VM near equipment, while others access dashboards and tools remotely in scheduled sessions.

Getting Started

Building a VMBOX image requires a Linux host with standard tools (parted, squashfs-tools, syslinux, virtualbox). The example below builds a demo image with two bundled apps (hello-world and web-terminal):

  1. Clone the repository
    git clone https://github.com/hackboxguy/vmbox.git
    cd vmbox
  2. Build the base rootfs
    sudo ./build.sh --mode=base --output=/tmp/alpine-build --version=1.0.1
  3. Build the APP partition
    sudo ./scripts/build-app-partition.sh \
      --packages=configs/hello-web-terminal-package.txt \
      --output=/tmp/alpine-build/app \
      --rootfs=/tmp/alpine-build/rootfs
  4. Create disk image with APP partition
    sudo ./scripts/03-create-image.sh \
      --rootfs=/tmp/alpine-build/rootfs \
      --output=/tmp/alpine-build \
      --ospart=600M \
      --datapart=200M \
      --apppart=300M \
      --appdir=/tmp/alpine-build/app/app
  5. Fix ownership of build output
    sudo chown -R $(id -u):$(id -g) /tmp/alpine-build
  6. Convert to VirtualBox VM
    ./scripts/04-convert-to-vbox.sh \
      --input=/tmp/alpine-build/alpine-vbox.raw \
      --vmname=vmbox-hello-webterm-demo \
      --appdir=/tmp/alpine-build/app/app \
      --force \
      --memory=1024
  7. Start the VM on Linux
    VBoxManage startvm "vmbox-hello-webterm-demo" --type headless
  8. Or export as OVA for distribution
    VBoxManage export "vmbox-hello-webterm-demo" -o "vmbox-hello-webterm-demo.ova"

After boot completes (typically ~30-60 seconds depending on host resources), open http://localhost:8000 to access the System Management Dashboard.

Tip: Add --serial to step 6 to see boot messages in the terminal. To package your own apps, create a custom package list and pass it to build-app-partition.sh in step 3. See the repository README for the full build guide and the VM App Design Guide for creating custom web apps with the recommended structure and UI/UX style to integrate seamlessly with the VMBOX framework.

Use Cases

  • Internal tool distribution — Package web dashboards, APIs, and line-of-business tools as portable VMs
  • Enterprise self-hosted apps — Deliver browser-based workflows without per-user host dependency setup
  • LLM-powered applications — Deliver AI-driven tools as self-contained VMs that run locally without cloud dependencies
  • Lab equipment interfaces — Browser-based control panels for test setups shared across teams
  • Optional embedded/hardware workspaces — Web-based serial terminals, CAN tools, and device management where USB passthrough is enabled
  • Training and demos — Hand out OVA files that work identically on every machine

SOURCE CODE

github.com/hackboxguy/vmbox — build system, rootfs overlay, system management UI, and example apps