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Phase 4 — Wire IMU I2C + scan

Add SDA / SCL and confirm the LSM6DSO answers at 0x6A. Power and straps from Phases 2–3 stay on.

Firmware

Changed. New folder firmware/04-i2c-scan/. Do not edit 01-hello. Pins SDA=8 SCL=18.

Preconditions

  • Checkpoint 3 passed
  • Straps: CS→3V3, SDO→GND
  • Unplug USB while seating the two data jumpers

4.1 Data wires

Phase 4 — I2C wires

S3 IMU
GPIO8 SDA
GPIO18 SCL

Both wires or nothing — one alone → found none. Leave IMU left row open. Do not wire TFT SPI yet.

4.2 Flash scanner

Stop any serial monitor on COM first.

cd firmware/04-i2c-scan
pio run -e esp32-s3-n16r8 -t upload --upload-port /dev/ttyACM0

Connected to ESP32-S3 on /dev/ttyACM0:
…
Hash of data verified.
Hard resetting via RTS pin...
========================= [SUCCESS] Took 9.17 seconds =========================

pio device monitor -b 115200 --port /dev/ttyACM0

seismo i2c-scan — phase 4
SDA=GPIO8 SCL=GPIO18 expect=0x6A (CS→3V3 SDO→GND)
--- i2c scan ---
found 0x6A
found 0x7E
devices=2

Expect 0x6A and 0x7E every scan. Pass on 0x6A. 0x7E is not the IMU.

4.3 If no device

  • Confirm both wires seated (see above)
  • Recheck SDA/SCL not swapped
  • Try SDO→3V3 (address becomes 0x6B) and re-scan
  • Shorter jumpers; shared GND confirmed

Checkpoint 4

  • [x] Serial scan lists 0x6A (or documented 0x6B fallback)
  • [x] Address stable across resets
  • [x] Logged in lab-log.md

Stop here until checkpoint passes.

Next: Phase 5 — Accel stream