What if you could watch pictures come out of thin air — no computer, no fancy SDR, just a $4 microcontroller and a bit of code? This project turns a Raspberry Pi Pico into a standalone SSTV decoder that takes an audio feed from your radio and displays images live on a tiny screen. It’s one of those “because I can” builds that reminds you just how far a few lines of C code and a soldering iron can go.
What Is SSTV?
Slow Scan Television (SSTV) is a way to transmit still images over radio. It’s been around since the early space missions, and hams still use it today — you’ll hear it on 14.230 MHz if you spin the dial on a weekend. The signal sounds like an old dial-up modem, but inside that noise is a picture waiting to be decoded.
“Each transmission encodes a single image using audio tones between 1200 Hz and 2300 Hz. The receiver decodes those tones back into pixel brightness and color.”
Why the Pico?
The Raspberry Pi Pico is cheap, fast, and has just enough horsepower to handle real-time FFTs for decoding SSTV. With a small display attached — like a 1.8″ ST7735 SPI screen — it becomes a self-contained visual decoder that fits in the palm of your hand.
Parts You’ll Need
- Raspberry Pi Pico (or Pico W)
- 1.8″ ST7735 or similar SPI TFT display
- 3.5 mm audio jack for radio input
- Optional: small speaker for monitoring audio
- A few resistors and jumper wires
Tip: You can feed the Pico directly from your radio’s speaker output — just make sure to pad it down with a voltage divider so the input stays under 3.3 V.
How It Works
The Pico listens to the incoming audio through its ADC pin, performs a fast Fourier transform (FFT) to detect tone frequencies, and maps those to pixel color values. The image is drawn line-by-line on the display in real time as the transmission comes in.
The code supports popular modes like Martin M1 and Scottie 1. With a good signal, you’ll see the image slowly appear from top to bottom — just like decoding SSTV in software, but this time, no laptop required.
Schematic and Code
Everything you need — including the C source code, wiring diagram, and prebuilt UF2 file — is available here:
View Project on GitHub
Flash the UF2 onto your Pico, wire up the display and audio jack, and you’re ready to start decoding images off the air. Plug the audio into your HF rig, tune to 14.230 MHz, and wait for someone to send a picture.
Optional Add-Ons
- 3D-printed enclosure for field use
- Battery power pack for portable ops
- OLED display for signal strength
- Headphone passthrough to monitor audio
Want to test without transmitting? Play an SSTV sample audio file from your phone into the Pico — it’ll decode it just like a real signal.
Final Thoughts
There’s something magical about seeing images decoded from pure audio, especially when it’s running on a board smaller than a matchbox. The Raspberry Pi Pico proves that you don’t need a computer to explore radio experiments — just curiosity, patience, and a good antenna.