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PRD-225 COM Radio

The PRD-225 is a hardware VHF COM radio panel modelled on the Garmin GTR-225 — a dual-concentric tuning knob, a 256×64 greyscale OLED display, and a full row of function buttons, all connected to MSFS 2024 through SimLinkHub and a CAN bridge.

The PRD-225 front panel

What it does​

  • Active and standby frequencies, shown large on its own OLED display, exactly like the real radio it's modelled on.
  • Dual-concentric tuning — the outer ring steps whole megahertz, the inner knob fine-tunes by the current channel spacing (25 kHz or 8.33 kHz).
  • Direct frequency entry — jump straight to a known frequency by dialing in each digit, rather than spinning through the whole band.
  • Flip-flop between active and standby, the same as a real radio.
  • Nearest Airports browser — see nearby airports and their COM frequencies live, sourced from your Little Navmap database, and load one straight into standby.
  • Monitor and squelch indicators, channel spacing toggle, and COM1/COM2 radio selection.

Display zones during normal operation

Controls at a glance​

Every control labelled

The dual-concentric tuning knob handles both coarse and fine tuning in one place:

Dual-concentric tuning knob

Full operating instructions​

Every button, mode, and display state is covered in detail in the Pilot's Guide — the same document included with the physical unit.

Firmware​

The PRD-225's firmware is open — see the STM-FlightSim-PRD-225-V1 repository. It runs on an STM32F072C8T6.

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