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Hardware

This section describes the main blocks of the iW-Beacon, taken from the project schematic (iW-iBeacon).

Board overview​

The iW-Beacon is organized into four blocks: the nRF52832 radio SoC, the sensors on the I2C bus, the power circuit with the nano-power timer, and the debug interfaces.

iW-Beacon board

3D model​

Drag to rotate, scroll to zoom.

Carregando modelo 3D...
3D model of the iW-Beacon (preliminary)

Processing and radio — nRF52832​

  • Nordic nRF52832 SoC (32-bit ARM Cortex-M4F)
  • Bluetooth 5 Low Energy
  • 32 MHz main crystal
  • 32.768 kHz crystal for the RTC and low-power timing
  • NFC pins available for tap pairing
  • internal DC/DC converter (DCC lines) for RF efficiency

The antenna output goes through a matching network (15 nH and 10 uH inductors) to the board antenna.

Integrated sensors​

Accelerometer — LIS3DH​

An ultra-low-power 3-axis inertial sensor, connected to the SoC over I2C/SPI with interrupt lines (INT1, INT2). Useful to wake the board on motion, and to detect tilt, orientation and tampering.

Temperature and humidity — SHTC3​

An SHTC3 sensor (Sensirion) on the I2C bus, with 2.2 k pull-ups. It provides temperature and relative-humidity readings for environmental telemetry directly in the beacon payload.

Both sensors share the same nRF52832 I2C bus, which simplifies the firmware and routing.

Power management (nano-power)​

The power circuit was designed for maximum battery life.

  • BT1 battery (coin-cell / battery type) as the primary source
  • nano-power TPL5110 timer (U4) that sets the wakeup interval
  • AO3401A P-MOSFET load switch (Q2), controlled by the timer
  • JP1 jumper to select the power mode
  • a capacitor bank (47 uF + 4.7 uF + 100 nF) to stabilize transmission peaks

How the cycle works​

  1. The TPL5110 keeps the board off during the programmed interval.
  2. At the end of the interval, it switches the MOSFET on and powers the nRF52832.
  3. The SoC wakes up, reads the sensors and transmits the BLE packet.
  4. The firmware signals DONE to the timer, which cuts power again.

This scheme reduces average consumption to microamperes, since the SoC only draws current during the short transmission window.

Interfaces and debugging​

  • SWD connector (J1, 3 ways: SWDCLK, SWDIO, GND) for flashing and debug
  • UART_TX / UART_RX console lines
  • I2C bus shared by the sensors
  • RESET button/line

Electrical characteristics (typical)​

ParameterValueNotes
Logic voltage3.3 Vsystem rail
Batterysingle cellcoin-cell / battery type (BT1)
Load switchAO3401AP-MOSFET controlled by the TPL5110
Average consumptionmicroampere rangedominated by the TPL5110 cycle
Crystals32 MHz + 32.768 kHzradio + RTC

The values above are derived from the schematic components. Actual consumption depends on the transmission interval, the RF power and the active sensors.

Best practices​

  • program the TPL5110 interval according to the trade-off between data freshness and battery life
  • use the accelerometer as a trigger for event-driven transmissions
  • keep the payload lean to shorten the active radio window
  • validate the antenna matching before closing the enclosure