Features

Five doors on the menu. About and Settings live in the corners. Only one decoder or logger runs at a time.

The RADIO face is AM/FM listening. USB/LSB is loaded when SSTV, Morse, or Watch need it. It is not a general SSB mode on RADIO.

There is hardware seek. There is no band-scan face and no station memory list. Those were removed on purpose.

Hardware

ESP32-S3 in the same touch-bus style as ESP32-DIV. Developed against Arduino-ESP32 core 2.0.10. Do not treat this as a 3.x project.

Core

• ESP32-S3 - UI, Wi-Fi AP, decoders, I2S mic
• SI4732-A10 - AM / FM / SW tuner (I2C). Probes 0x11 and 0x63 (SEN to GND or 3.3 V)
• ILI9341 2.8" - 240x320 portrait, rotation 2
• XPT2046 - touch on its own SPI bus, not shared with the TFT
• PAM8403 - class-D amp. Mute GPIO 7 before analog outs power up
• I2S MEMS mic - INMP441 / SPH0645 class, 16 kHz averaged down to 8 kHz
• 3x WS2812 on GPIO 38. Hue is locked to orange
• 3x tactile buttons - UP / OK / DOWN, active-LOW with internal pull-ups

GPIO map

Edit Pins.h if your PCB is different. TFT SPI pins must also match TFT_eSPI_User_Setup.h.

Audio tap (required for SSTV and Morse from the radio)

SI4732 LOUT -> 1 uF capacitor -> GPIO 1 (ADC). Two 100 kOhm resistors as a mid-rail bias, one to 3.3 V, one to GND.

Without this wire, RADIO still plays through the PAM8403, Homing still works from RSSI, and Watch can still log RSSI. SSTV and Morse from the radio will have nothing to decode. You can still feed those tools from the MEMS mic.

Speaker path: SI4732 LOUT/ROUT through DC-blocking caps into the PAM8403. Keep the amp shutdown pin under firmware control.

Buttons

Touch is primary. Three buttons are the fallback.

In a tool: tune is 1 kHz steps, OK flips USB/LSB (or PEAK on Homing), long OK goes back. Hold UP+DOWN from any face to return to the menu. There is no rotary encoder.

Flash with Arduino IDE

The sketch folder must be named Fennec. Stay on Arduino-ESP32 2.0.10. Core 3.x breaks the NeoPixel RMT code.

1. Install Arduino IDE 2.x.
2. Boards Manager: add https://espressif.github.io/arduino-esp32/package_esp32_index.json if needed, then install esp32 by Espressif. Use 2.0.10 if you can.
3. Tools -> Board -> ESP32S3 Dev Module.
4. Sketch -> Include Library -> Manage Libraries, install:
   • PU2CLR SI4735 (Ricardo Caratti)
   • TFT_eSPI (Bodmer)
   • XPT2046_Touchscreen (Paul Stoffregen)
5. Copy TFT_eSPI_User_Setup.h over Documents/Arduino/libraries/TFT_eSPI/User_Setup.h. The sketch does not include that file. TFT_eSPI reads it from its own library folder. Paste it by hand once.
6. Open Fennec.ino and click Upload.

Suggested Tools menu

First boot

• Hold OK while resetting, or send c on serial, to calibrate touch.
• Join Wi-Fi SSID Fennec and open http://192.168.4.1/.
• Serial at 115200. Send ? for commands.

Radio

FM, AM, shortwave. The chip's whole analog world, from long wave up through the broadcast bands, amateur stretches, and CB. Not airband. Not weather radio. Not VHF.

Tap FM, AM, or SW. The chips under the tabs are shortcuts: a full span, or Japan FM, or forty-nine meters. The big number is where you are. SEEK hunts a station. MUTE is a finger on the speaker. Volume lives on the bottom row.

Last place you were is remembered. Open RADIO tomorrow and you are still there.

RADIO is AM/FM listening, not general SSB. The SSB patch loads when SSTV, Morse, or Watch need USB/LSB.

SSTV

Shortwave still sends pictures. Slow-scan. A tone that paints a line, then another, until a face or a schematic is sitting on the glass.

Open SSTV. Fennec goes USB or LSB, listens for the VIS, and draws as the lines arrive. Martin M1/M2, Scottie S1/S2, Robot 36. Leave it on AUTO, or lock a mode if you already know the handshake.

Calling frequencies are on the keys:

RADIO listens through the tuner. MIC listens through the capsule. Hold a speaker to the mic if you must, and the amplifier goes quiet so Fennec does not copy itself. Nudge BFO until the picture locks. RESET if the image goes wrong. Walk away and come back: the picture is still there.

Needs the GPIO 1 audio tap, or MIC. Web BMP is at /api/sstv.bmp. Picture size is load-bearing. Don't casually change kSstvPic.

Morse

Dits and dahs on the air, and Fennec writes them down. A listener's copy, not a contest machine.

Open MORSE. Set the pitch to the tone you hear. That is PIT. Sideband with USB and LSB. BFO if the note sits off-center.

RADIO copies from the tuner. MIC copies from the capsule. The speaker mutes so the box does not hear itself. Hold the phone close. Echo is the enemy. Gaps fill, letters glue.

The first word waits a breath. Fennec is learning how fast they are sending. Then the text starts to run. Fifteen to thirty words a minute is the neighborhood.

Goertzel, 400-1200 Hz, 4 ms blocks. Pitch has to match the tone. Not reliable at QRQ or with a noisy speaker across the room.

Homing

You are not getting a compass bearing. You are getting a peak.

Open HOMING. A line crawls across the screen, about eight seconds of signal strength. The orange LEDs breathe with it. Walk. Turn the beam. When the trace climbs and the lights quicken, you are looking at the transmitter.

Tap PEAK to mark the high water and hunt again. A whip standing straight up will not point. You need a direction. You are the motor. Fennec is the meter.

RSSI sparkline only. Not Adcock, Doppler, or compass. No sidetone. ESP32-S3 has no DAC. You hear the radio, or nothing on MIC.

Watch

Some signals do not talk. They just appear.

Open WATCH. Park on a frequency: UVB-76, a known USB marker, or HERE, wherever you already sit. ARM it. When the carrier holds above the threshold, Fennec writes an event: time, frequency, how strong it got. Up to thirty-two of them, kept in flash.

Raise or lower the threshold. Clear the list when the night is done. This is a log for a shortwave listener, not a decoder of voices, and not a tool for anything that is not yours to hear.

Serial d dumps JSON. Events live in the same NVS namespace as band and volume.

Menu, About, Settings

Power on, and Fennec does not shout. One orange blink. The CiferTech mark on black sand. Then a quiet menu. Five tiles: RADIO, SSTV, MORSE, HOMING, WATCH. About and Settings live in the corners. Tap a tile when you are ready.

About

Who built it. What board. What chip. A mail, a GitHub, a site. Tap anywhere to go back.

Settings

Four taps. Wi-Fi access point on or off. When it is on, the address sits under the list. PIXEL, the three orange LEDs. BRIGHT, twenty percent at a time, never dark enough to lose the menu. TOUCH, if the glass and the finger disagree, or hold OK while it boots and walk the crosses.

Brightness 20-100, step 20. Hold OK at boot to calibrate. A short lock after Settings taps eats bounce so the page does not flicker.

Web remote

Same radio. Second glass.

Join the network named Fennec. Open a browser to http://192.168.4.1/. What you see is what the box is doing. Change a tab on the phone, and the LCD follows. Change the LCD, and the page follows.

RADIO on the web is the live tuner, speaker up, not the silent boot menu. SSTV shows the picture as it paints. Morse, homing, watch: the same tools, in your hand, across the room.

If you have a home network in the firmware, Fennec can join it too, take time from the internet, and put a clock in the header.

Set FENNEC_WIFI_AP_PASS (8+ characters) to encrypt the AP. Only one exclusive tool at a time, shared with the LCD.

HTTP

Serial

115200 baud. Send ? for help.

Config.h

Tunables. Pins stay in Pins.h.

It doesn't work

The long form of this list, plus what was intentionally removed, is in FENNEC.txt.

License

MIT, CiferTech 2026. See LICENSE.txt.

SI4732 programming follows Silicon Labs AN332 via PU2CLR SI4735. The SI4732-A10 SSB patch comes from that library. Don't redistribute Silicon Labs chip firmware as a commercial product.

Contact

CiferTech · twitter · github.com/cifertech/Fennec · cifertech.net