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Phase 3 — Power the sensors

Four wires: SHT40 and BMP390 supply only. TFT power from Phase 2 stays. No I2C data yet.

Firmware

Unchanged — firmware/01-hello/.

Preconditions

Checkpoint 2 passed. One SHT40 and one BMP390 on the breadboard. Unplug USB while seating jumpers.

Warning

Power the modules from 3V3 only — 5V on the logic can kill them. After wiring, check for heat and ~3.3 V on each VCC before trusting it.

Wires

Phase 3 — sensor power

From S3 To
3V3 SHT40 VCC / VIN / VN, BMP390 VCC / VIN
GND SHT40 GND, BMP390 GND

Tap the breadboard 3V3 / GND star (how the board is tied) — don’t daisy-chain module-to-module for power. Silk may say VCC, VIN, VN, or 3Vo — same 3V3 rail as TFT VDD. Leave SDA / SCL open until Phase 4.

Check

Plug COM. Modules cool. Meter ≈ 3.3 V on each sensor VCC. TFT backlight still on. Hello still prints.

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

weather hello MAC=28:84:85:8C:D0:40 uptime_ms=1624

Checkpoint 3

  • [x] Those four sensor power wires only (TFT power still on)
  • [x] ~3.3 V on each VCC, no heat
  • [x] Hello still prints
  • [x] Lab log

Next: Phase 4 — I2C scan