What I learned selling 2,500 MIDI recorders: Hardware is not so hard

Original Article ↗ Hacker News Discussion ↗

A solo developer’s success selling 2,500 units of a simple ESP32-based MIDI recorder prompts debate over how hard modern hardware really is when you lean on mature modules, Chinese assembly houses, and modest product scope. Commenters probe the hidden complexity behind the project: 200k lines of firmware and app code, manufacturing tooling, anti-counterfeit measures using secure elements and per-device keys, and regulatory hurdles like FCC/CE testing. Many conclude that small, well-scoped consumer devices are now highly achievable for software engineers, but warn that hardware becomes truly difficult at larger scales, with analog complexity, strict compliance, logistics, cash flow, and cloning risks.

Software vs. Hardware Difficulty

  • Many commenters argue the product’s hardware is intentionally simple (ESP32 module, MIDI circuitry, SD, basic peripherals), so “hardware isn’t hard” only applies at this low-complexity end.
  • Others stress that “real” hardware difficulty shows up with complex analog, RF, high-speed digital, or multi-board systems and at larger scales (tolerances, EMI/EMC, logistics, cash flow).
  • Several note that most of the work was in software (firmware, mobile app, manufacturing tooling), reinforcing that hardware complexity was constrained by design.

Codebase Size and Architecture

  • The codebase is 200k lines, split between app (85k) and firmware (~110k), excluding vendor libraries.
  • Commenters are surprised at the size; some compare with much smaller personal ESP32 projects.
  • The author says long compile/flash cycles and feature creep were major early mistakes; cross-platform firmware stubs on desktop would have sped iteration.

Anti-Counterfeiting and Security

  • Strong interest in “have a strong anti-counterfeit strategy.”
  • Device uses a secure element (STSAFE), per-device random IDs/product keys, and app-side enforcement that only talks to genuine devices, mostly offline.
  • Discussion covers how keys are provisioned at scale (HSMs vs preprogrammed ICs), threat models involving the factory, and why many commercial devices need unique IDs/keys.
  • Multiple people request a dedicated write-up; some question whether anti-counterfeiting is even necessary at this niche scale.

Compliance and Certification

  • Device reportedly has FCC testing and CE self-certification; using pre-certified radio modules keeps cost down (~$5k cited as a typical budget).
  • Hardware engineers emphasize that EMI/EMC and regulatory work is often the truly “hard” part of shipping electronics and can require redesigns.
  • Others note many cheap imports skip proper testing, but small domestic makers are more exposed to regulatory risk.

Hardware Design Choices & Critiques

  • Detailed critiques target choices like AMS1117 regulators, ESD protection coverage, resistor sizes on MIDI outputs, coin-cell vs supercap, USB-B for power, and lack of USB-C.
  • The author responds with tradeoff reasoning: availability, user demographics (older users benefit from clear, non-interchangeable ports), and long RTC retention.

Manufacturing, Tooling, and Fulfillment

  • Manufacturing tooling includes flashing, key provisioning, and per-unit hardware testing (battery, SD, clock, anti-counterfeit IC, etc.).
  • Prototyping and low-volume injection molding are discussed; ~1000–2500 units is framed as a reasonable threshold where custom molds start to make sense.
  • Fulfillment at this scale is “annoying but manageable”; too small yet for most 3PLs.

Customer Reception and Use

  • Multiple owners report very positive experiences: “it just works,” records everything to SD, and the app’s playback and practice tracking are praised.
  • Users appreciate that core recording works without the app and that recordings are standard MIDI files, easing long-term viability concerns.

Learning Resources and Getting Started

  • New hardware builders are pointed to online electronics channels, PCB design communities (e.g., KiCad chat/subreddits), and even LLMs for PCB review as surprisingly useful.
  • A recurring meta-point: hardware is much more accessible than a decade ago, but still becomes hard as complexity and scale increase.