ESP32-C3-Mini (Lolin C3 Mini Mainboard)

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A board under the board-centric repo convention. This repo is organized with the board as root:

esp32-c3-mini/
├── README.md          # this file: all hardware info for this board
└── <project>/         # one directory per project built on this board (named by capability)
    ├── CMakeLists.txt / main/ / sdkconfig.defaults / main/idf_component.yml
    └── README.md      # project description + build/flash commands

Key points of the convention:

• Board directory name = board name (kebab-case); the root README covers hardware only, never project content;
• Each project directory builds standalone: it ships the full ESP-IDF project trio (top-level CMakeLists, main/, sdkconfig.defaults); cd <project> && idf.py build produces the firmware;
• Projects share no code; when commonality is needed, copy first, and consider extracting a shared component only once things stabilize.

Firmware baseline norms (mandatory fleet-wide)

1. Watchdog: mandatory. Tasks subscribe to the ESP-IDF TWDT and feed it periodically;
2. Web/API firmware upgrade (OTA): mandatory where the hardware allows. WiFi plus 4 MB flash fit dual OTA slots, so every project ships a web upgrade path.

Project	Watchdog	Web/API OTA
blink	✅ per-task TWDT (5 s panic)	✅ dual OTA slots + streaming POST /ota
weather-clock	✅ per-task TWDT (5 s panic)	✅ dual OTA slots + streaming POST /ota

---

Board Overview

Item	Value
Module/chip	ESP32-C3FH4 — RISC-V single-core @ 160 MHz (4 MB flash in-package, no PSRAM)
Flash	4 MB (embedded)
PSRAM	None
Wireless	2.4 GHz WiFi b/g/n + Bluetooth 5 (LE)
USB	Native USB Type-C (USB-Serial-JTAG: console + flashing, no bridge chip)
Onboard LED	WS2812B RGB = GPIO7 (addressable; Arduino official board def PIN_RGB_LED=7)
Buttons	BOOT = GPIO9 (standard C3 strapping, hold at power-up for download), RESET
Breakout	12× digital IO (D1 mini shield-compatible form factor)
Dimensions	34.3 × 25.4 mm (D1 mini form factor, accepts Lolin/D1 mini shields)
Factory	Ships with MicroPython by default; this repo uses ESP-IDF (v6.0)
Source	Board facts from the Wemos/Lolin official page + the Arduino official board definition — the most common board named "esp32-c3-mini"; if your carrier board is a different vendor, trust the actual board

Pinout Diagram (USB-C pointing up, front/component-side view; functional pin map)

                 ┌─ USB-C ─┐
                 │ [WS2812]│
                 │  =GPIO7 │   ESP32-C3FH4
                 │ [RST]   │   4MB flash (in-package, no PSRAM)
                 │ [BOOT]  │   12× IO (D1 mini form factor)
                 └─────────┘
  The physical pad order is not documented as a table on the official
  page — follow the official wemos.cc pinout diagram for wiring; do not
  infer wiring from this figure.

Key points (pin functions per the Arduino official board definition lolin_c3_mini/pins_arduino.h):

• WS2812 RGB = GPIO7; BOOT = GPIO9; UART0 TX=GPIO21 · RX=GPIO20;
• I2C: SDA=GPIO8 · SCL=GPIO10; SPI: SS=GPIO5 · MOSI=GPIO4 · MISO=GPIO3 · SCK=GPIO2;
• ADC: A0–A5 = GPIO0–5;
• GPIO18/19 = USB D-/D+ (generic C3 constraint) — do not repurpose; GPIO2/8/9 are strapping pins — mind their power-on levels when attaching peripherals.

Caveats

• No USB-UART bridge: the serial port is the C3's native USB-Serial-JTAG (console/flashing/JTAG on one port);
• Download mode: hold BOOT (GPIO9) while plugging USB / pressing RESET;
• No PSRAM — plan large buffers around the ~400 KB SRAM class (same league as luatos-esp32c3);
• The board ships with MicroPython — flashing ESP-IDF firmware replaces it (re-flashable);
• D1 mini shield compatibility is this board's differentiator (3.3 V logic — mind compatibility with older 5 V shields).

Project Index

Project	Description
blink	Baseline/test firmware: WS2812 (GPIO7) status-color rotation + BOOT interaction + web maintenance page (provisioning/OTA) + TWDT watchdog
weather-clock	ST7735 0.96" TFT (160x80) + AHT30 desktop clock: NTP time, temp/hum over a rotating random background (ported from the user's Arduino sketch, same wiring) + web provisioning/OTA