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• R909-tester: What It Is, What It Does, and Why You Should Care

  nobcha • 3 小時前 • 0 comments

  So, I tried to turn the leftover RP2040 boards into a useful prototype.

  What It Is

  R909-tester is a modular, low-cost instrument platform built around the Raspberry Pi RP2040 Zero. It's designed to be a handy companion on your workbench, combining several useful measurement functions into a single, compact device.

  What It Does (The Functions)

  Currently, it packs four main tools:

  Continuity Tester: Quick and audible checks for your circuits.

  Capacitance Meter: Measures capacitors in a practical range.

  Frequency Counter: Counts signals – with some limitations I'll discuss in a later log.

  Diode Identifier: Identifies and tests diodes.

  All of this is controlled through a simple OLED display and a rotary encoder. No complex menus – just select the function and go.

  Why I Built It (The Design Intent)

  This project was born from a simple question: "How far can I take a practical instrument using just an RP2040 and minimal external parts?"

  It's not about replacing a $500 multimeter. It's about exploring the boundaries of what's possible with this cheap and powerful microcontroller, and creating something genuinely useful for everyday electronics work.

  The Modular Concept

  I also designed it with modularity in mind. The core hardware and software are structured so that adding new features – or even replacing existing ones – should be straightforward. This is why I'm planning to explore adding an external ADC for a SINAD measurement add-on in the future.

  What's Next (The Roadmap)

  Short-term: Refining the existing features and improving the frequency counter (more on that in its own log!).

  Long-term: Designing a custom PCB, building a proper enclosure, and exploring the SINAD add-on.

  So, that's the plan. If you're interested in seeing how far a cheap RP2040 zero can go as a test instrument, stick around. It's going to be a fun ride.

• The Real Reason I Built R909-tester (It Wasn't Planned)

  nobcha • 1 天前 • 0 comments

  This project didn't start with a grand plan to build a multi-function tester. It started with a disappointment.

  I was working on the ESP32-C3 version of my SINAD indicator. The ADC performance was… not great. So I thought: "What if I try the RP2040? Maybe its ADC is better suited for this kind of measurement." https://nobcha23.hatenablog.com/entry/2025/06/10/211826

  The RP2040's ADC turned out to be slightly better – but still not enough for serious measurement work. I realized that for real accuracy, I would need an external ADC. And that meant dealing with I2S, which turned out to be its own can of worms.

  So there I was: a handful of RP2040 boards sitting on my desk, no clear use for them, and a bit of frustration. https://nobcha23.hatenablog.com/entry/2026/04/01/194146

  That's when I thought: "Why not turn them into something useful? A simple tester, maybe? Just to put these boards to work."

  And that's how R909-tester began – not as a brilliant idea, but as a way to salvage some boards and learn something along the way. It turned out to be a fun project after all.
  https://chitose6thplant.fc2.page/r909-tester/

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