SmartMTR-ESP32

Based on SmartMTR by Dariusz Socha, SQ5X The design of this dial — the round face, the S-meter arcs, the side gauges, the center dock, its layout and styling — comes from SmartMTR, created by Dariusz Socha (SQ5X). This port is published with his kind permission. All credit for the SmartMTR design is his: https://smartmtr.net/

A FlexRadio controller on the Elecrow CrowPanel 2.1" HMI ESP32 Rotary Display (DHE03921D: ESP32-S3R8, 480×480 round IPS touch screen, rotary dial that also clicks). The face is modeled on SmartMTR by Dariusz Socha, SQ5X: S-meter arcs for two slices, SWR/COMP/PWR/MIC needles, and the frequency readout, with a dock of touch tiles in the middle.

It plugs into the PC running AetherSDR by USB. AetherSDR's CTR2 Proxy applet relays it to the radio over the CTR2 USB link v0 (spec), so the knob is an independent SmartSDR API client. It binds to the AetherSDR (or SmartSDR) station and drives that station's slices. No Wi-Fi setup is needed.

Controls

There are two kinds of input, and this document keeps their names apart:

• On the screen: tap (a short touch), touch-and-hold, and swipe.
• On the dial: turn it, one detent at a time, and click it (push it down until it clicks).

Input	Action
Turn the dial	Tune the active slice by its step
Click the dial	Next tuning step (10 Hz → 10 kHz); in parameter mode, back to tuning
Click-and-hold the dial (0.6 s)	Tune lock on/off for the active slice; the face shows LOCKED and turning does not tune
Tap a tile	Turning the dial adjusts that parameter (yellow outline); tap it again to tune
Touch-and-hold NR / NB / ANF	Toggle it on or off
Touch-and-hold AGC or AF	Step AGC mode (off/slow/med/fast)
Touch-and-hold FILT	Next tuning step
Tap a slice's TX label	Make that slice the transmit slice (gray = not TX, red outline = TX, filled = on air)
Swipe down	Open the menu (below)

Menu

Swipe down anywhere on the face to open it. It is a scrolling list of values for the active slice and the transmitter, and every row can be changed without leaving it:

• Levels (RIT, filter edges, squelch, NR amount, RF power, …) have a fader.
• Lists (Mode, antennas, Band, NR/ANF mode) have a stepped fader.
• On/off settings have a switch. Rows with both a level and an on/off setting (RIT, XIT, Squelch, WNB, APF, Compander, Monitor) have both.
• AGC has a fader for the amount and a mode button (Off/Slow/Med/Fast).

By touch:

• Swipe the list up or down to scroll it. A vertical swipe that starts on a fader still scrolls the list.
• Drag a fader sideways to set the value; levels go to the radio as you drag, and a list choice is sent when you lift your finger.
• Tap a switch or the AGC mode button to flip it or step it.
• Tap a row to put it in edit for the dial (yellow outline); tap it again to release it.

With the dial:

• Turn to move the highlight (white outline) down or up the list; the list scrolls with it.
• Click to put the highlighted row in edit (yellow outline). Turning then changes it: a level steps, a list previews its next choice in yellow, and an on/off row turns on (clockwise) or off (anticlockwise).
• Click while editing: on a row with a switch it flips the switch, and on AGC it steps the mode; both stay in edit. On any other row it leaves edit, and sends a previewed choice at once. Otherwise a choice is sent when the dial rests for 0.7 s.
• Click-and-hold leaves edit and drops a previewed choice. With nothing in edit, it closes the menu.

To close it, tap the grip at the bottom, swipe up from the grip, click-and-hold the dial (with nothing in edit), or leave it for 8 s.

Rows:

• Receive: Mode, RX antenna, Band, RIT, Filter low/high, AGC (mode and amount), Squelch, NR mode (NR/NRL/NRS/RNN/NRF) and amount, ANF mode (ANF/ANFL/ANFT) and amount, WNB, APF (CW only), Mute, Pan, Diversity, DAX channel, Tune lock.
• Transmit: RF power, Tune power, Mic gain, Compander, Monitor, TX antenna, XIT, and in CW also CW speed, CW pitch and Break-in.

Nothing in the menu keys the transmitter. VOX and TUNE are deliberately left out. To add a row, add one entry to the table in main/menu_items.c.

S-meters

The bars and their white peak markers use AetherSDR's SmartMTR ballistics (main/meter_ballistics.c, ported from SmartMtrWidget):

• Bar: jumps up in about 18 ms and sags back in about 270 ms.
• Peak marker: shows the highest level of the last 3 s. Once that peak leaves the window, the marker glides down at a steady rate, and it never sits below the bar.
• Scale: linear in dB from S0 to S9+40, so every dB is the same length and S9 sits a little past the middle.

Center: spectrum or tiles

With an AetherSDR that sends it, the center shows a 32-bar spectrum (with peak hold) of the receive audio you are hearing, like SmartMTR's: after the radio's DSP, AetherSDR's noise reduction and its RX chain up to and including the EQ. While transmitting it shows your transmit audio in red, across the TX filter width. Otherwise it spans 0 Hz to the active slice's filter width, so a 600 Hz CW filter shows 0–600 Hz and a 6 kHz SSB filter 0–6 kHz (at most 12 kHz, the limit of the 24 kHz audio). Bar heights are in dB, and the bars are spaced logarithmically in frequency like an audio analyzer, starting from a low edge of about a sixtieth of the span. The scale relabels itself to match. Tap it to show the tiles below instead; they return to the spectrum after 8 s unused, unless a tile is on the dial. A sideways swipe switches either way. Without a spectrum the tiles stay.

The spectrum is a CTR2 link extension, negotiated through HID Feature report 0x02 (see AetherSDR docs/ctr2-usb-relay-design.md, "Extensions"). A CTR2 never offers or receives it.

Tiles: AF (audio level), AGC (threshold), FILT (width, 50 Hz per detent, about the passband center), and NR / NB / ANF (level).

Connections (back of the board)

Connector	Pins	Use
USB-5V-IN (4-pin MX1.25)	VCC, D−, D+, GND	Power and native USB to the PC, through the MX1.25-to-USB cable that ships with the board. This carries the HID link to AetherSDR and is also the flashing port.
UART (4-pin)	RX, TX, 5V, GND	Firmware logs at 115200. Use a 3.3 V USB-serial adapter, and leave its power pin off the 5V pin.
I2C (4-pin)	SCL, SDA, 5V, GND	Spare. It is the same bus as the touch controller (0x15) and the PCF8574 (0x21), so an added device needs another address.
RESET, BOOT		Flashing, below.

Build and flash

Requires ESP-IDF 6.0 or later.

. ~/esp/esp-idf-v6.0.3/export.sh
idf.py build

The firmware takes over the native USB port as a HID device, so the board's USB serial port is not available while it runs. To flash: hold BOOT, tap RESET, release BOOT. The board then enumerates as the ROM's USB serial port.

idf.py -p /dev/ttyACM0 flash

Tap RESET to run it. Within about 3 s the board re-enumerates as AetherSDR AETHER_KNOB. If it is still USB JTAG/serial debug unit, the reset after flashing left it in download mode: tap RESET again, or run python -m esptool --port <port> --after watchdog-reset chip-id. Logs go to UART0 on the 4-pin UART header (115200).

Use with AetherSDR

1. Connect AetherSDR to the radio.
2. Open the CTR2 Proxy applet, set Mode to USB, pick AetherKnob (AETHER_KNOB), and press Start.
3. The knob's screen goes from "Waiting for AetherSDR" to the meter face once it has bound to your station.

On Linux the applet offers to install a udev rule the first time. The rule needs AetherSDR with AetherKnob support (the AETHER_KNOB product string).

Layout

Path	What
main/board.c	Display (ST7701S over 3-wire SPI + RGB), touch, dial turn (PCNT) and click (PCF8574)
main/usb_link.c	TinyUSB vendor HID, device side of CTR2 link v0, radio task
main/ctr2_link.{c,h}	Link framing, MIT, copied from AetherSDR tools/ctr2-firmware-reference
main/flex_api.c	SmartSDR API client: bind, slices, commands, VITA-49 meters
main/ui.c	LVGL 9 face
main/menu_items.c	Menu rows: keys, ranges, commands (host-tested)
main/menu.c	Swipe-down menu screen
test/	Host test of the API client (make -C test check)
test/preview/	Renders the screens on the PC (make faces) and drives the menu with a scripted finger and dial (make touchtest)
docs/smartsdr-api-notes.md	Protocol facts the client relies on, from FlexLib

Status

What is tested:

• The firmware builds.
• The API client passes host tests against a scripted radio session.

Not yet verified on hardware:

• Display bring-up.
• Encoder counts per detent (DIAL_COUNTS_PER_DETENT in board.c).
• Touch orientation.
• Meters over the relay's UDP path. No CTR2 has exercised that path on hardware yet.

License

GPL-3.0; see LICENSE. The two ctr2_link files are MIT. The design credit to Dariusz Socha, SQ5X, in NOTICE.md must be kept in any copy or derivative.