Our first PCB

Note: This post documents our hardware design journey. Final implementation: ESP32-S3-based board with ports for 4 sensors (pH, temperature, NPK, moisture) as per government voucher deliverables.

Prototyping can only take us so far. It’s time for Dragonfly Lake to move our hardware into the next stage of maturity.

While many teams jump straight to fully custom boards, we’re taking a different approach for our first PCB.

We want our PCB to be compatible with existing development boards, for a very practical reason.

It makes the product easier to own and maintain: if a module ever fails, the client can replace it quickly without having to swap the entire device.

Some of these components are:

  • USB connectivity, so clients can flash new firmware versions when needed
  • Power regulation and protection handled by a widely available module
  • A proven Wi‑Fi module and antenna design, with easy sourcing and replacements

ESP32-S3 Super Mini

We decided to use the ESP32-S3 Super Mini for our first board.

It’s ultra-compact (22.5 x 18 mm), widely available, and keeps replacements simple.

It’s packed with features:

  • Dual-core Xtensa LX7 processor at 240 MHz
  • 512 KB SRAM, 4 MB flash
  • 14 GPIO pins with ADC, I2C, SPI, UART support
  • Type-C USB port
  • WiFi 802.11b/g/n and Bluetooth 5 (LE)
  • Built-in PCB antenna
  • Onboard RGB LED (WS2812)

It’s compatible with MicroPython, Arduino, and ESP-IDF.

Ports

We opted for JST connectors to connect our device to external sensors and power sources.

Ports (as per project deliverables):

  • 1x 5V JST Power port: accepts external 5V power source;
  • 1x Analog port: for capacitive soil moisture sensor;
  • 2x Digital ports: for digital sensors and outputs;
  • 2x UART/RS485 ports: for RS485 communication modules (NPK and soil pH sensors);
  • 2x I²C ports: for external sensors (e.g. temperature and humidity sensors).

The dual UART/RS485 ports provide dedicated connections for soil analysis sensors. The dual I²C ports enable multiple temperature and humidity sensors. Analog provides simple moisture readings. Digital ports offer flexibility for additional sensors or control signals.

All ports use JST-PH (2.0 mm) - common, reliable standard compatible with thousands of sensors and modules.