USB‑C powered ESP32‑C3 controller board with regulated 3.3 V supply, USB ESD protection, buttons/status LEDs, ambient-light I²C sensing, and a 555-driven capacitive soil-moisture electrode.
# MuseGrow V2.1
MuseGrow is a compact USB-C plant monitor built around the ESP32-C3. Its narrow PCB blade goes directly into the soil, so no external soil-probe cable or JST connector is required. Covered interdigitated copper electrodes measure moisture capacitively, while a VEML7700 reads ambient light.
## Board
- Electronics head: 44 mm × 34 mm
- Integrated probe: 14 mm × 50 mm
- Overall outline: 44 mm × 84 mm
- Stackup: 2-layer, 1.6 mm FR-4
- Supply: USB-C 5 V input and AP2112K 3.3 V regulation
- MCU: ESP32-C3-WROOM-02-N4 with native USB data
- Sensors: covered capacitive soil probe and VEML7700 ambient-light sensor
- Controls: reset, boot, and pair/user pushbuttons
- Indicators: green power LED and blue firmware-controlled status LED
- Protection: USBLC6-2SC6 USB data ESD array and ESD5Z5V0 VBUS TVS
- Routing: current tscircuit 0.0.2794 autorouter, latest router version, 10× effort
- Assembly: every fitted component and every test point is on the top side; the bottom side carries routing and ground copper only
The schematic uses three automatically laid-out sheets: Power and USB, Controller and Controls, and Light and Integrated Soil Probe. The circuit source contains no `schX` or `schY` placement properties.
## How the soil probe works
The two comb-shaped copper electrodes are part of the PCB and remain covered by solder mask. Soil moisture changes their capacitance. U5, a TLC555, converts that capacitance into a frequency through R14 and R15; the ESP32 reads the frequency on GPIO1 and converts it to a moisture percentage after dry-soil and wet-soil calibration.
Only the blade below the **MAX SOIL** line should enter the soil. Keep the electronics head, USB-C connector, buttons, light sensor, and LEDs dry. A conformal coating or sealed enclosure around the head is recommended for real plant use.
## Power and connection
USB-C supplies 5 V and the regulator produces 3.3 V for the ESP32 and sensors. The board has no battery charger in V2. Firmware can send readings directly over Wi-Fi through the local router; a phone hotspot is only needed where no normal Wi-Fi network is available. Bluetooth can be used for first-time setup.
## Test points
The small top-side pads expose 5 V, 3.3 V, GND, UART RX/TX, EN, I²C SDA/SCL, and the soil-frequency signal. They are for factory testing, programming recovery, and calibration; they require no connector and are not fitted parts.
## Build and verification
```sh
bun install
bun run typecheck
bun run build
tsci check netlist index.circuit.tsx
tsci check pin_specification index.circuit.tsx
tsci check placement index.circuit.tsx
tsci check shorts index.circuit.tsx
```
V1 and V2 artifacts remain in `fabrication/`, `previews/`, `fabrication-v2/`, and `previews-v2/`. The top-assembly V2.1 manufacturing and review files are in `fabrication-v2-top/` and `previews-v2-top/`. Review the Gerbers, assembly drawing, BOM, and pick-and-place data with the chosen fabricator before ordering. Keep copper, enclosure walls, batteries, and cables out of the marked ESP32 antenna area.