Cobra-19XS-VFO-DDS-VFO

ESP32-based digital VFO, meter, and menu firmware for a Cobra 19XS-style radio.

What’s included

• Flashable PlatformIO project
• ESP32 Arduino firmware in src/main.cpp
• Dual OLED support:
  • 128x64 main frequency screen
  • 128x32 Cobra-style meter screen
• Separate preview/status screen for quick-glance frequency and mode info
• Encoder menu, memory slots, meter modes, and voltage calibration

Project layout

• platformio.ini — build configuration
• src/main.cpp — firmware source
• main code — legacy source snapshot from the original upload

Flashing

1. Open the folder in VS Code with PlatformIO installed.
2. Select the esp32dev environment.
3. Build and upload.

Command line:

pio run
pio run -t upload

Screen preview

Main screen

27.000.000 MHz
AM   RX
^ step underline moves with the selected tuning step

Meter screen

S/RF
S1  S3  S5  S7  S9  +10  +20  +30
pixel-dotted Cobra 148 GTL-style meter face

Preview screen

STATUS     RX
FREQ 27.000 MHz
MODE AM STEP 1k

Controls

• Short press encoder: cycle tuning step
• Long press encoder: open menu
• Encoder rotation: tune or navigate menus
• Long press from main screen: toggle meter invert
• Meter mode, brightness, invert, and voltage calibration are in the Meter menu

Wiring notes

• Si5351 CLK0 -> radio mixer/VFO injection point
• GPIO35 -> audio/S-meter tap
• GPIO34 / GPIO26 -> PTT detect/key
• GPIO36 -> voltage divider input
• Shared ground is required

Notes

• This firmware is written for an ESP32 Dev Module target.
• The voltage input must be scaled with a proper divider before connecting to GPIO36.
• Radio modifications should only be done by experienced users.