Icom RC-28 USB encoder controller for FlexRadio SmartSDR and AetherSDR
FlexRC-28 connects an Icom RC-28 USB remote encoder to a FlexRadio FLEX-6000/8000 series radio running SmartSDR or AetherSDR for Windows. It replaces the need for a mouse when tuning, gives you one-touch mode and band cycling, and adds PTT latch for comfortable ragchew operation.
- Dial tuning — velocity-sensitive, slow (10 Hz/step) and fast (100 Hz/step) modes
- Tuning Sensitivity — determines how much physical rotation is required before a frequency change is sent to the radio; at the rightmost (maximum) position every detected wheel movement triggers a step, while sliding left requires progressively more rotation before a step fires — useful for high-gearing the dial so a full rotation only nudges the frequency a small amount
- Tuning Step — determines the frequency step size applied on each detected rotation increment; moving the slider left selects a smaller step (e.g. 1 Hz) while the rightmost position selects a larger step (e.g. 100 Hz); together with Tuning Sensitivity, sliding both controls toward the left makes the frequency change very slowly and allows fine, precise tuning with the RC-28 wheel
- Step snapping — switches between step sizes with automatic frequency boundary snap
- Snap to 1 kHz — detects panadapter clicks and snaps to nearest 1 kHz; ignores mouse wheel and dial tuning
- PTT — momentary press-and-hold, or hold 2.5 seconds to latch TX on; tap again to release
- Mode cycle — step through LSB → USB → CW → AM
- Band cycle — step through 160m to 6m with automatic mode selection per band
- RIT — toggle on/off, tune with dial, display shows offset; clear with button hold
- Link LED — solid green when connected to radio
- TX LED — lights during transmit, stays lit when latched
- F1/F2 LEDs — mirror app state (fast mode, RIT active)
- Radio discovery — automatically finds FlexRadio on local network; if exactly one radio is found it is selected and connected automatically at startup
- All button assignments configurable — assign any action to any button press or hold
- Settings persisted — reconnects automatically on next launch
- Windows 10/11
- FlexRadio FLEX-6000 or FLEX-8000 series running SmartSDR for Windows
- Icom RC-28 USB remote encoder
See INSTALL.md for step-by-step instructions covering both the installer and running from source.
- Plug in the RC-28 via USB
- Start SmartSDR and open a slice
- Launch FlexRC-28 — the RC-28 will be detected automatically
- Enter your radio's IP address (or select from the discovery dropdown) and station name
- Click Connect
- The Link LED on the RC-28 will go solid green
| Button | Action |
|---|---|
| PTT press & hold | Transmit (momentary) |
| PTT hold 2.5s | Latch TX on — tap to release |
| F1 press | Toggle fast/slow tuning (5x or 1x step size) |
| F1 hold | Cycle mode (LSB → USB → CW → AM) |
| F2 press | Toggle RIT |
| F2 hold | Cycle band (160m → 80m → … → 6m) |
All assignments can be changed in the Button Assignments panel. Available actions:
- PTT (Transmit)
- Toggle Fast/Slow Tuning
- Lock/Unlock Dial
- Cycle Mode (LSB/USB/CW/AM)
- Cycle Band (160m–6m)
- Toggle RIT
- Clear RIT
- Snap to 1 kHz
- No Action
Enable the Snap to 1kHz toggle to snap to the nearest 1 kHz frequency 0.6 seconds after dial rotation stops.
- Short press and hold — transmits while held, releases on button release
- Hold 2.5 seconds — when PTT Latch button is on on, latches TX after 2.5 seconds; the TX badge changes to TX LATCH
- Tap PTT while latched — immediately releases TX
| Band | Frequency | Mode |
|---|---|---|
| 160m | 1.900 MHz | LSB |
| 80m | 3.750 MHz | LSB |
| 60m | 5.372 MHz | USB |
| 40m | 7.150 MHz | LSB |
| 30m | 10.120 MHz | USB |
| 20m | 14.225 MHz | USB |
| 17m | 18.128 MHz | USB |
| 15m | 21.285 MHz | USB |
| 12m | 24.940 MHz | USB |
| 10m | 28.500 MHz | USB |
| 6m | 50.150 MHz | USB |
FlexRC-28/
├── index.html UI
├── package.json
└── src/
├── main.js Electron main process
├── preload.js IPC bridge
├── rc28.js RC-28 HID driver (WebHID)
├── flex.js SmartSDR TCP API client
└── controller.js RC-28 to radio action mapping
Reverse-engineered from USB capture (USBPcap/Wireshark). The RC-28 presents as a USB HID device (VID 0x0C26, PID 0x001E).
| Byte | Meaning |
|---|---|
| 0 | Report type — always 0x01 |
| 1 | Dial velocity (0 = stopped, 1–16+ = speed) |
| 2 | Always 0x00 |
| 3 | Dial direction: 0x01 = CW (freq up), 0x02 = CCW (freq down) |
| 4 | Always 0x00 |
| 5 | Button bitmask (active-low): bit 0 = PTT, bit 1 = F1, bit 2 = F2 |
Button state values:
| Value | State |
|---|---|
0x07 |
Idle — all released |
0x06 |
PTT held |
0x05 |
F1 pressed |
0x03 |
F2 pressed |
[0x01][ledByte][0x00 x 30]
LED byte bitmask (all active-low):
| Bit | LED |
|---|---|
| 0 | TX/PTT LED |
| 1 | F1 LED |
| 2 | F2 LED |
| 3 | Link LED |
| Value | State |
|---|---|
0x0F |
All LEDs off |
0x07 |
Link LED on |
0x06 |
Link + TX on |
0x05 |
Link + F1 on |
0x03 |
Link + F2 on |
| Action | Command |
|---|---|
| Subscribe to slice status | sub slice all |
| Subscribe to TX status | sub tx all |
| Tune frequency | slice tune <id> <MHz> |
| Set mode | slice set <id> mode=<mode> |
| Set RIT offset | slice set <id> rit_freq=<Hz> |
| Enable/disable RIT | slice set <id> rit_on=1/0 |
| PTT on/off | xmit 1/0 |
Connects via TCP to port 4992. Radio discovery uses UDP broadcast on port 4992.
Built with Electron. Uses Electron's built-in WebHID API for RC-28 communication — no native build tools required.
RC-28 HID protocol reverse-engineered using USBPcap and Wireshark.
SmartSDR TCP/IP API documented at github.com/flexradio/smartsdr-api-docs.
Thanks to Steve Walker CerberusSolutions for the original edition of this project
GNU General Public License v3.0 — see LICENSE for details.
If the app is not behaving as expected, run it in debug mode to see the raw SmartSDR API traffic in the activity log.
From source:
npm start -- --debugInstalled app (run from PowerShell or Command Prompt):
& "$env:LOCALAPPDATA\Programs\FlexRC-28\FlexRC-28.exe" --debugIn debug mode the activity log will show all raw status messages from the radio, prefixed with ⬡. This output is useful when reporting issues.
- Check the RC-28 is plugged in before launching the app
- Check Windows Device Manager — it should appear as Icom RC-28 REMOTE ENCODER
- Try a different USB port or cable
- Confirm SmartSDR is running and a slice is open
- Check the IP address — use the discovery dropdown if unsure
- Confirm the radio and PC are on the same subnet
- FlexRC-28 does not currently support SmartLink remote connections (a VPN to your home network will work)
- Check the station name matches what is shown at the bottom of the SmartSDR window
- Disconnect and reconnect