Sensor Breakout Board — BME280 (KiCad)

A compact (21 × 16 mm) 2-layer breakout board for the Bosch BME280 temperature / humidity / pressure sensor, designed from schematic to manufacturable layout in KiCad. The repository contains the full design source, bill of materials and fabrication instructions, plus a write-up of every design decision for reproducibility.

 ┌───────────────────────────┐
 │ 3V3 ○                     │
 │ GND ○   [R][R][R] [C][C]  │   21 x 16 mm, 2 layers
 │ SDA ○      ┌────┐         │   BME280 in LGA-8
 │ SCL ○      │BME │         │   I2C @ address 0x76
 │ SDO ○      └────┘         │
 └───────────────────────────┘

Design summary

• Interface: I2C (CSB pulled high selects I2C mode; SDO pulled low sets address 0x76). SDO is broken out on the header so the address can be changed to 0x77 externally.
• Pull-ups: 4.7 kΩ on SDA/SCL — suitable for 100–400 kHz on short buses.
• Decoupling: separate 100 nF X7R capacitors on VDD and VDDIO, placed close to the sensor.
• Ground: solid GND pours on both layers with stitching vias under the sensor for a low-impedance return path.
• Header pinout: 3V3 · GND · SDA · SCL · SDO (2.54 mm, breadboard-friendly).

Repository layout

├── hardware/
│   ├── sensor-breakout.kicad_pro   KiCad project
│   ├── sensor-breakout.kicad_sch   schematic
│   └── sensor-breakout.kicad_pcb   2-layer PCB layout
├── fabrication/
│   ├── BOM.csv                     bill of materials with MPNs
│   └── README.md                   Gerber/drill generation (kicad-cli)
├── docs/DESIGN.md                  full design write-up (DFM, decisions)
└── LICENSE

Opening the project

1. Install KiCad 7+.
2. Open hardware/sensor-breakout.kicad_pro.
3. In the PCB editor press B to refill the copper zones, then run DRC.

Manufacturing

See fabrication/README.md — one kicad-cli command produces a Gerber ZIP accepted by JLCPCB, PCBWay or OSH Park. All parts are basic/extended parts at JLCPCB; the board can also be hand-assembled with a hot plate or hot-air station (the LGA-8 is the only tricky part — see the soldering notes in the design write-up).

License

MIT — see LICENSE.