CRT Test Pattern Generator Fits in Your Pocket

A CRT test pattern generator built around an ESP32 dev board is a neat answer to a very specific problem: You want to evaluate an old TV quickly, but you do not want to drag a whole console (or other video source) to someone’s garage or a thrift store. Nicholas Murray’s pocket tool outputs PAL/NTSC composite video and lets you cycle through patterns with a button press.

CRT Test Pattern Generator: What It Is

The build uses an ESP32-based M5StickC PLUS2 and a small add-on board that provides composite video out via a simple resistor network and an RCA jack.
 

In the project write-up, Hackaday notes the practical details that make it useful in the field: a large button cycles patterns, a side switch selects NTSC or PAL, and the unit’s own color screen mirrors the selected output so you know what you are sending without guessing.

How It Works, and How You Load It

On the software side, the source code on GitHub describes the feature set plainly: PAL/NTSC support, multiple patterns, RGB565 color, and a built-in battery/screen combination intended for quick CRT checks. Firmware flashing is designed to be low-friction: you connect over USB and use a browser installer, with the note that you may need USB-serial drivers depending on your setup.

Why It’s Handy for Retro Gear

For CRT buying and basic triage, patterns are a fast way to spot geometry issues, convergence problems, color balance oddities, and general “is this thing healthy?” behavior—before you commit to carrying a heavy set home. The M5StickC PLUS2 itself is tiny (48×24.0×13.5 mm), includes a 1.14-inch display, and packs a 200 mAh battery, which helps explain why this CRT test pattern generator can stay genuinely pocketable rather than turning into “portable” in the marketing sense. If you want the underlying hardware details, M5Stack’s device spec sheet is the quickest reference.

If this sort of tool is your kind of bench-adjacent retro hobby, you’ll probably also enjoy browsing Elektor’s Test & Measurement coverage for more practical instrumentation ideas: