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Wiring Guide

Overview

Three modules connect to the XIAO ESP32-C3:

  • ATGM336H GPS module via UART (2 data wires + power)
  • ADXL345 accelerometer via I2C (2 data wires + power)
  • Battery (2 wires)

Total: 10 connections, with shared 3V3 and GND lines.

Pin Connections

XIAO ESP32-C3          ATGM336H GPS
┌─────────────┐        ┌───────────┐
│         D7 ─┼────────┤ TX        │
│         D6 ─┼────────┤ RX        │
│        3V3 ─┼──┬─────┤ VCC       │
│        GND ─┼──┬─────┤ GND       │
│             │  │  │  └───────────┘
│             │  │  │
│             │  │  │  ADXL345
│             │  │  │  ┌───────────┐
│         D4 ─┼──┼──┼──┤ SDA       │
│         D5 ─┼──┼──┼──┤ SCL       │
│             │  ├──┼──┤ VCC       │
│             │  │  ├──┤ GND       │
│             │  │  │  └───────────┘
│             │  │  │
│             │  │  │  3x AA Battery
│             │  │  │  ┌───────────┐
│         5V ─┼──┼──┼──┤ + (red)   │
│             │  │  └──┤ - (black) │
└─────────────┘  │     └───────────┘
                 │
          Shared 3V3 and GND rails

XIAO ESP32-C3 Pin Reference

Board label GPIO Used for
D4 GPIO6 ADXL345 SDA (I2C)
D5 GPIO7 ADXL345 SCL (I2C)
D6 GPIO21 GPS TX→RX
D7 GPIO20 GPS RX→TX
3V3 — Power for GPS + accelerometer
5V — Battery input (regulated to 3.3V)
GND — Common ground

Power Options

Option A: 3x AA batteries

  • Connect battery holder red (+) wire to XIAO 5V pin
  • Connect battery holder black (-) wire to XIAO GND pin
  • 4.5V is regulated down to 3.3V by the XIAO's onboard regulator
  • Replace batteries when voltage drops below ~3.0V

Option B: Li-Po + TP4056 charger

  • TP4056 B+ → Li-Po red (+)
  • TP4056 B- → Li-Po black (-)
  • TP4056 OUT+ → XIAO 5V
  • TP4056 OUT- → XIAO GND
  • Charge via USB-C on the TP4056 module
  • Do NOT connect USB to XIAO and TP4056 at the same time

Important Notes

  • The ATGM336H is 3.3V only — do NOT connect VCC to 5V
  • GPS TX connects to XIAO RX (D7), and GPS RX connects to XIAO TX (D6) — they cross
  • Keep wires short to reduce noise, especially the GPS UART lines
  • If using a breadboard, share 3V3 and GND via the power rails