Vibration Node Design Notes
Architecture
Battery JST PH input -> AP2112K-3.3 LDO -> 3V3 rail -> Seeed XIAO ESP32S3, ADXL355, OLED connector.
Power budget
Estimated 3V3 loads:
- XIAO ESP32S3: use 240 mA typical active / up to 500 mA short WiFi TX bursts as sizing envelope.
- ADXL355: approximately 0.2 mA typical.
- OLED module: approximately 20 mA typical.
- Pull-ups and regulator overhead: ADXL355 SCLK
- SPI_MISO_ADXL: XIAO GPIO8 / D9 -> ADXL355 MISO
- SPI_MOSI_ADXL: XIAO GPIO9 / D10 -> ADXL355 MOSI
- SPI_CS_ADXL: XIAO GPIO4 / D3 -> ADXL355 CS, with 10k pull-up
- ADXL_DRDY: XIAO GPIO3 / D2 OLED SDA, 4.7k pull-up
- I2C_SCL_OLED: XIAO GPIO6 / D5 -> OLED SCL, 4.7k pull-up
Layout requirements for next phase
- Use 2-layer compact board if SPI is kept low/moderate speed; bottom layer should be mostly uninterrupted GND fill.
- Place ADXL355 close to a board edge, away from XIAO ESP32S3 antenna and regulator.
- Keep SPI SCLK/MISO/MOSI/CS short, same layer where possible, routed as a group over solid ground.
- Put ADXL355 decoupling immediately at VSUPPLY/VDDIO/V1P8DIG/V1P8ANA pins.
- Put OLED connector on an accessible edge and keep I2C away from the regulator and antenna region.
- Use four mounting holes close to corners for rigid mechanical coupling.