smokescreen/README.md

smokescreen

Feed third-party BBQ probes (MEATER, ThermoWorks, Combustion) into a pellet grill's wired probe jacks, so they show up as native probes on the grill display and in the vendor app — with working target-temp alarms and Keep Warm.

Developed and tested against a Traeger Ironwood (2022 touchscreen WiFire), but the technique is just PT1000 emulation, so it should carry to any grill using the same 3.5 mm PT1000 jacks — Pit Boss, Camp Chef, GMG and friends.

The name is the mechanism: the grill is looking at a probe that isn't there.

How it works

your probes ──BLE──> Raspberry Pi ──I²C──> AD5272 rheostat ──3.5mm──> Traeger jacks 1 & 2

The Ironwood's wired jacks take PT1000 RTDs — 1000 Ω at 0 °C, ~3.85 Ω/°C, a published standard curve. So instead of breaking Traeger's wireless pairing, we just be a PT1000: read your probe over BLE, compute the resistance a real PT1000 would have at that temperature, and present it to the jack.

No protocol to reverse, nothing to re-break after a firmware update, and the grill's own logic works because as far as it knows, nothing unusual happened.

Why not MITM the wireless probes — and why one nRF52840 dongle can't anyway — is in docs/PROTOCOL_NOTES.md.

Start here

Before writing code or buying parts, do Step 0 in docs/HARDWARE.md: put a plain 1.2 kΩ resistor in a 3.5 mm plug, plug it into jack 1, and check the grill reads ~127 °F. That one experiment validates this entire design in ten minutes with a multimeter and a junk-drawer resistor.

Quick start

python3 -m venv .venv && .venv/bin/pip install -e '.[dev]'

Run the whole pipeline with no hardware at all — simulated probes, no I²C writes:

cp config.example.yaml config.yaml && .venv/bin/smokescreen run --dry-run

jack1=20.3C/1079ohm [Simulated probe 1]  jack2=17.2C/1067ohm [Simulated probe 2]

The PT1000 reference table, for bench work with a multimeter:

.venv/bin/smokescreen table

On the Pi, with hardware wired and calibrated:

.venv/bin/smokescreen run

Adding a probe vendor

Subclass ProbeSource, emit ProbeReading objects, register it in sources/__init__.py. Nothing else changes — the router and the PT1000 emulator never learn what hardware produced a number.

Source	Status
simulator	Works. Synthetic cook curve with a stall, for development
thermoworks	RFX via ThermoWorks Cloud. Needs pip install '.[thermoworks]'
meater	Implemented from community reverse engineering — verify on the bench
combustion	Stub. Open published spec, easiest to finish

With more probes than jacks — four RFX probes into two jacks — list what's visible and pin the two you want:

.venv/bin/smokescreen discover

Unimplemented sources raise rather than returning plausible-looking numbers. The grill acts on these values, so a driver that silently invents data would be worse than one that refuses to start.

Safety

Stale, missing, or implausible readings drive the channel cold, never hot. A stuck-hot channel could convince the grill a cook finished early; a stuck-cold one can only look obviously wrong. Details and the reasoning are in docs/HARDWARE.md.

This is a hobby project driving a fire with reverse-engineered numbers. Keep a real probe in the cook until you have several successful runs behind you.

Layout

src/smokescreen/
  pt1000.py              IEC 60751 curve math — the part that must be right
  models.py              ProbeReading, ChannelState
  router.py              which probe drives which jack
  bridge.py              orchestration loop
  sources/               probe backends (add vendors here)
  outputs/               rheostat driver + PT1000 emulator
docs/HARDWARE.md         wiring, BOM, calibration, Step 0
docs/PROTOCOL_NOTES.md   what we know per vendor, and how much to trust it