Haptic Feedback
CYM includes an optional ERM (eccentric rotating mass) vibrator motor driven through the onboard SC8002B class-D audio amplifier on the SPEAK header (GPIO 26). Because the alert is completely non-audible, it lets you operate the device in occupied or sensitive environments — pocket, bag, or flat on a desk — without drawing attention.
| Feature | Pattern | Behaviour |
|---|---|---|
| BT Lookout | 3 × 1-second bursts, 500 ms gaps | Fires on every watchlist MAC/OUI match |
| BT Locator | Continuous pulse every 500 ms | Strength scales 10–100% with RSSI |
| WiFi Deauth | 1 × 3-second solid pulse | Fires at attack launch as non-audible confirmation |
| CC1101 Fox Hunt | 150 ms bursts, 100% strength | Pulse rate scales with signal level |
| nRF24 Fox Hunt | 150 ms bursts, 100% strength | Pulse rate scales with carrier detect rate |
| RF433 Fox Hunt | 150 ms bursts, 100% strength | Pulse rate scales with 433 MHz edge activity |
| RSSI | Approximate distance | Motor strength |
|---|---|---|
| −40 dBm or stronger | Within ~1 m | 100% |
| −55 dBm | ~1–3 m | ~58% |
| −69 dBm | ~5 m (edge of range) | 10% |
| Below −69 dBm | Too far / obstructed | Silent |
Strength updates every 500 ms. The formula is linear in dBm: strength = 10 + (RSSI + 69) × 90 / 29, clamped to 10–100 %.
The vibrator is an optional hardware add-on. The firmware detects it automatically — if the motor is not installed, all haptic calls are no-ops.
| Role | Part | Notes |
|---|---|---|
| Series rectifier | 1N5819 Schottky diode | Anode → VO1 (SPEAK pin 1), cathode → motor +. Half-wave rectifies the BTL output. |
| Flyback protection | 1N4148 signal diode | Cathode → motor +, anode → motor −. Suppresses back-EMF spikes on each PWM off-cycle. |
| Motor | Mini ERM vibration motor, 3 V nominal | Coin or cylindrical form factor. |
| Header connector | JST GH 1.25 mm 2-pin | 1.25 mm pitch only — the 1.0 mm SH connector is too small and will not fit. |
Why the SC8002B amp? ERM motors draw 100–200 mA at startup, well beyond the ~20 mA continuous GPIO limit. The SC8002B buffers the GPIO signal and drives up to ~1.5 A peak from the board's power rail. GPIO 26 sources only ~1 mA into the amp input. Never connect a motor directly to a GPIO pin.
The SC8002B outputs a BTL (bridge-tied load) differential signal. The 1N5819 half-wave rectifies it so the motor sees clean DC-biased pulses. The 1N4148 flyback diode clamps the inductive spike produced by the motor on each PWM off-cycle — without it, the spike would damage the SC8002B output stage.
PWM parameters: LEDC timer, 333 Hz, 8-bit. Maximum effective duty is 50% (the BTL half-wave rectification means higher duty gives no additional torque). Strength slider in Settings → Vibrator Test maps 10–100% → 13–128/255 duty counts.
Rectifier circuit — 1N5819 series diode and 1N4148 flyback
Motor wired to SPEAK header with diode circuit in place
Assembly wrapped and ready to install
Motor installed in the device
Settings → Vibrator Test exposes:
- ON / OFF buttons — manual control for confirming the motor is wired and working
- Strength slider (10–100%) — adjusts duty cycle in real time while running; lets you find the minimum strength that reliably spins the motor in your specific motor/mounting combination
The strength setting persists within the session. BT Locator saves and restores your test strength so the locator's RSSI-scaled range isn't affected by a prior test value.
- Fox Hunt / BT Locator in a jacket pocket — the variable pulse rate is easy to read by feel after a few minutes of practice. Faster = closer, stronger = closer. You can navigate to a target without ever looking at the screen.
- BT Lookout during a walk-through — the 3-burst pattern is distinctive and hard to confuse with accidental contact. Hold the device loosely; the bursts transmit clearly through fabric.
- Deauth confirmation — the 3-second solid pulse means you felt the attack launch without looking down. Useful when you're watching a target's screen for client drops while simultaneously operating CYM.