Flea-Scope: $18 Source Available USB Oscilloscope, Logic Analyzer and More [pdf]

Original Article ↗ Hacker News Discussion ↗

Licensing, Patents, and “FOSS” Terminology

  • Project uses a mix of All Rights Reserved, public domain, MIT, and some non-commercial components; parts are also patented.
  • Several commenters say “FOSS” / “open source” is misleading here; “source available” or “with published design” is preferred.
  • Debate over whether public domain counts as “free” or “open source” and how jurisdiction (US vs EU) complicates public-domain claims.
  • Arguments over GPL: some see copyleft as protecting freedom; others view it as commercially restrictive.

Capabilities and Architecture (Clarifications)

  • Actual specs: ~18 Msps, one analog channel, ~12‑bit ADC but effective 10–11 bits, plus multiple digital channels and waveform generation.
  • Implemented on a PIC32MK, not STM32; no FPGA involved.
  • Designed as a simple, low-cost mixed-signal tool, not a high-performance scope.

Educational Goals and Use Cases

  • Creator states the main goal is one unit per student in a classroom that already has PCs/Chromebooks.
  • WebUSB/JavaScript UI avoids software installs; a “deep dive” BASIC mode allows interactive experiments and even autorun projects (e.g., games, reflow-oven controller).
  • Some users plan to carry it for field/debug work (factories, automotive sensors) due to tiny form factor.

Cheap vs “Real” Oscilloscopes

  • Many point out that very capable 100–200 MHz bench scopes (Rigol, Siglent, etc.) are now ~$300–$450 and vastly superior for serious work.
  • Counterpoint: there is still a big gap between $18 and $300; cheap gear is vital for learners, students, and low-income regions.
  • Ongoing argument: cheap tools can either lower the barrier and encourage experimentation or frustrate beginners due to limitations and poor reliability.

Global Affordability and Context

  • Several comments emphasize that $300 is near or above a monthly minimum wage in many countries; $18 can still be significant but is far more reachable.
  • Comparisons made to $2–$50 toy scopes and $80–$100 handhelds; flea-scope’s multi-channel digital IO is seen as unusually strong at this price.

Safety and USB Grounding

  • Warnings about ground loops and shared USB ground when probing mains or high-voltage circuits; isolation or proper probes recommended.
  • The documentation explicitly advises using a USB isolator.

Alternatives, Ecosystem, and Data Export

  • Mentioned alternatives: $13 logic analyzers (with sigrok), FNIRSI handheld scopes, EspoTek Labrador, other MCU-based boards like “buck50,” and full-featured bench scopes.
  • Flea-scope does not focus on protocol decoding or recording in the UI, but raw data can be pulled over serial/USB and analyzed in Python or other tools.

Hardware Design and Tooling Feedback

  • Schematic/PCB are in DipTrace; some would prefer KiCad for hacker-friendliness.
  • Reviewers note the simple 2‑layer board, lack of ground pour, and routing choices likely leave analog performance and EMC margin on the table, but overall see it as an impressive, instructive design for the cost.