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A coin-cell-powered 915 MHz wireless sensor node — an ATmega328P driving a Silicon Labs Si4455 sub-GHz transceiver, with onboard sensing and a hand-tuned RF matching network. Designed end-to-end in KiCad: schematic → impedance-matched RF front-end → PCB layout.
CoinCellSensor is a tiny battery-powered telemetry board: it wakes, samples its sensors, transmits a packet over the 915 MHz ISM band, and drops back to sleep to sip coin-cell power.
| MCU | ATmega328P |
| Radio | Silicon Labs Si4455 (EZRadio sub-GHz transceiver, 915 MHz ISM) |
| Sensing | onboard temperature + pressure, status LED |
| Power | single coin cell, low-power duty-cycled operation |
| EDA | KiCad — schematic + PCB layout |
The Si4455 only hits its range and efficiency with a properly impedance-matched front-end. I implemented the direct-tie matching + harmonic-filter topology between the radio and the antenna:
Choosing the L/C values, keeping the RF trace controlled-impedance, and getting the ground return right is the same class of problem I now work on at scale (RF coexistence and antenna de-sense). This board is where that started.
📷 Photos of the assembled board are coming — drop them in
Images/and they'll slot in here.
CoinCellSensor.sch — full schematicCoinCellSensor.kicad_pcb — PCB layout*.lib / *.net / *.pro — KiCad symbol libraries, netlist, project filesBuilt by Frank Walsh — electrical engineer (RF / PCB / embedded).
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