Phase 3 — GNSS power¶

Two wires: GNSS supply from the 3V3 star, plus the antenna. No UART data yet — just prove the module lives without browning out the bus. TFT power from Phase 2 stays.

Firmware¶

Unchanged — firmware/01-hello/. Tracker: Firmware.

Preconditions¶

Checkpoint 2 passed (TFT still powered). ATGM336H + antenna on the desk. Unplug USB while seating jumpers.

Warning

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

Wires¶

From star	To ATGM336H
3V3	VCC
GND	GND

Tap the same breadboard 3V3/GND star as the TFT (Hardware — Breadboard). Silk on many modules reads VCC · GND · TX · RX · PPS (order varies — trust the labels). Leave TX RX PPS open until Phase 4. Fit the antenna (U.FL pigtail / ceramic patch as supplied) before you expect any later fix.

Check¶

Plug USB and check the port — it may have moved after the unplug:

ls /dev/ttyUSB*

/dev/ttyUSB0
# or /dev/ttyUSB1 — use whichever ls shows

Then eyeball the power:

Module cool — if warm or smelling, unplug and recheck polarity / 5V.
Meter ≈ 3.3 V on ATGM336H VCC to GND if you have one.
TFT backlight still on.

Finally, confirm hello still ticks (bus not browned out):

cd firmware/01-hello
pio device monitor -b 115200 --port /dev/ttyUSB0

--- Terminal on /dev/ttyUSB0 | 115200 8-N-1
--- Quit: Ctrl+C | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H
gnss-field hello MAC=8C:94:DF:6D:C9:5C uptime_ms=...
gnss-field hello MAC=8C:94:DF:6D:C9:5C uptime_ms=...

Some modules blink an LED after a while outdoors; indoors it may stay dark — OK for this phase. NMEA comes in Phase 4.

Checkpoint 3¶

[x] GNSS VCC/GND from the star only (TX RX PPS open)
[x] Antenna attached
[x] ~3.3 V, no heat; TFT backlight still on
[x] Hello serial still alive
[x] Logged in Lab log

Next: Phase 4 — NMEA raw