Notes

Hardware notes for small products

All (52)Hardware (7)Firmware (28)PCB Design (7)Embedded UI (3)Product Design (1)3D Printing (0)Mochi (6)

Hardware

HC-05 vs HM-10 vs BLE 5.0: Which Bluetooth Module Should You Choose?

Compare HC-05, HM-10, and BLE 5.0 modules by Bluetooth Classic, BLE GATT, UART, phone support, range, power, and integration for Arduino, ESP32, and IoT projects.

6 min read·September 6, 2026

Hardware

ESP32 Beginner Guide – P1: What Is ESP32 and Choose ESP32

Learn the difference between ESP32 chips, modules, and development boards, then choose an ESP32-C3, ESP32-S3, or classic ESP32 board without buying hardware you do not need.

9 min read·September 2, 2026

Hardware

18 Common ESP32 Errors and How to Fix Them – Part 1

How I troubleshoot eight common ESP32 problems: flashing, boot mode, brownouts, serial, GPIO, I2C, SPI, and custom PCB bring-up.

9 min read·August 31, 2026

Hardware

What Is a MEMS Microphone? From a Silicon Diaphragm to ESP32 Audio

Learn how MEMS microphones work, how analog, PDM, and I2S outputs differ, and how to avoid PCB, power, and acoustic-port mistakes.

8 min read·August 10, 2026

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Hardware

ESP32 Battery Power Design: From USB-C Charging to the 3.3V Rail

Review an ESP32-S3 battery power path from USB-C and TP4056 charging to protection, load sharing, 3.3V regulation, and load budget.

12 min read·August 6, 2026

Hardware

ESP32-C3 or ESP32-S3: Which Chip for a Robot with a Screen and Audio?

Comparing ESP32-C3 and ESP32-S3 on GPIO, RAM, PSRAM, USB, I2S, and LVGL headroom, with a concrete recommendation for a basic Mochi build and a Mochi AI build.

5 min read·August 5, 2026

Hardware

First Notes On Hardware Design For Small Products

Initial principles for designing hardware for a small product: scope, power, PCB layout, firmware, and debugging.

3 min read·July 20, 2026