diff --git a/docs/ble-bridge-wiring.md b/docs/ble-bridge-wiring.md
index d25f0c8..fa1971b 100644
--- a/docs/ble-bridge-wiring.md
+++ b/docs/ble-bridge-wiring.md
@@ -1,15 +1,21 @@
 # BLE Bridge Wiring — ESP32-S3 + 2× MAX485
 
-Transparent BLE-to-RS422 bridge for the Winegard Carryout G2 satellite dish.
+Transparent BLE-to-RS422 bridge for the Winegard Carryout G2 satellite dish,
+with optional IMU and barometric sensors for orientation and refraction correction.
 
 ## Parts
 
+**Bridge (required):**
 - ESP32-S3-DevKitC-1-N16R8
 - 2× MAX485 TTL-to-RS485 module
 - 1× SparkFun Bidirectional Logic Level Converter (BOB-12009, BSS138-based)
 - RJ-12 6P6C straight-wired cable with breakout
 - Hookup wire / jumpers
 
+**Sensors (optional):**
+- 1× GY-9250 (MPU-9250) — 9-axis IMU (accelerometer + gyroscope + magnetometer)
+- 1× BMP388 — barometric pressure + temperature
+
 ## Schematic
 
 ```
@@ -113,6 +119,103 @@ The firmware is the same regardless of whether the RS-422 transceiver is a
 MAX490 (single full-duplex chip) or two MAX485s (locked half-duplex pair).
 It only sees UART TX/RX on GPIO17/18.
 
+## Sensors — I2C Bus
+
+The MPU-9250 and BMP388 share a single I2C bus on GPIO8 (SDA) / GPIO9 (SCL).
+Both run at 3.3V directly from the ESP32, no level shifting needed.
+
+```
+                    I2C Bus (3.3V, 400kHz)
+                    ─────────────────────
+
+ESP32 3V3 ──┬──────────────────┬─── MPU-9250 VCC
+             │                  └─── BMP388 VCC
+             │
+             ├── 4.7KΩ ── SDA bus ──┬── MPU-9250 SDA
+             │                      └── BMP388 SDI
+             │
+             └── 4.7KΩ ── SCL bus ──┬── MPU-9250 SCL
+                                    └── BMP388 SCK
+
+ESP32 GPIO8  (SDA) ──── SDA bus
+ESP32 GPIO9  (SCL) ──── SCL bus
+
+ESP32 GND ──┬── MPU-9250 GND
+             └── BMP388 GND (SDO to GND = addr 0x76)
+
+MPU-9250 AD0 ── GND  (I2C address = 0x68)
+BMP388   SDO ── GND  (I2C address = 0x76)
+```
+
+The 4.7KΩ pull-ups are shared — one pair for the whole bus. Many breakout
+boards include onboard pull-ups already; if both the GY-9250 and BMP388
+boards have them, the combined parallel resistance (~2.3KΩ) is still fine
+for 400kHz I2C at 3.3V. Only add external pull-ups if neither board has them.
+
+### MPU-9250 (GY-9250) — 9-Axis IMU
+
+| I2C Address | 0x68 (AD0 → GND) |
+|-------------|-------------------|
+| VCC | 3-5V (onboard LDO) |
+| Interface | I2C (up to 400kHz) or SPI |
+
+**What it provides for satellite tracking:**
+
+- **Magnetometer (AK8963):** Compass heading for automatic north alignment.
+  Eliminates manual alignment of dish base "BACK" marking to true north.
+  Apply local magnetic declination to convert magnetic north → true north.
+- **Accelerometer:** Gravity vector → tilt angle = elevation. Independent
+  verification of the dish firmware's reported EL position.
+- **Gyroscope:** Angular rate during slews. Detect oscillation, overshoot,
+  and vibration for tuning the leapfrog overshoot compensation algorithm.
+
+**Mounting considerations:** The magnetometer is extremely sensitive to nearby
+ferrous metals and electromagnetic interference from motors. Mount on the
+fixed base plate, away from motor housings, with a known axis aligned to the
+dish's reference direction. Rigid mounting — any flex between sensor and dish
+structure introduces measurement error.
+
+### BMP388 — Barometric Pressure + Temperature
+
+| I2C Address | 0x76 (SDO → GND) |
+|-------------|-------------------|
+| VCC | 3.3V |
+| Pressure range | 300-1250 hPa |
+| Pressure resolution | ±0.01 hPa (±8 cm altitude) |
+| Temperature accuracy | ±0.5°C |
+| Interface | I2C (up to 3.4MHz) or SPI |
+
+**What it provides for satellite tracking:**
+
+- **Atmospheric refraction correction.** Radio signals bend as they pass
+  through the atmosphere, especially at low elevation angles. The amount of
+  bending depends on air pressure and temperature. At 15° elevation (the
+  Trav'ler's minimum), refraction shifts apparent position by ~0.2°.
+  Standard refraction models (Bennett, Saemundsson) take pressure and
+  temperature as inputs — the BMP388 provides both in real time.
+- **Temperature monitoring.** Ambient temperature at the dish for thermal
+  drift awareness and electronics health monitoring.
+
+**Refraction formula (simplified Bennett):**
+```
+R = 1/tan(el + 7.31/(el + 4.4)) × (P/1010) × (283/(273 + T))
+```
+Where R is refraction in arcminutes, el is apparent elevation in degrees,
+P is pressure in hPa, T is temperature in °C. At el=15°, P=1013, T=20°C:
+R ≈ 3.4 arcmin ≈ 0.057°. Small but meaningful for narrow-beam antennas.
+
+## Full GPIO Map
+
+| GPIO | Function | Interface | Notes |
+|------|----------|-----------|-------|
+| 17 | RS-422 TX | UART1 TX | → Level shifter → MAX485₁ DI |
+| 18 | RS-422 RX | UART1 RX | ← Level shifter ← MAX485₂ RO |
+| 8 | I2C SDA | I2C | MPU-9250 + BMP388 (shared bus) |
+| 9 | I2C SCL | I2C | MPU-9250 + BMP388 (shared bus) |
+| 38 | RGB LED | WS2812 | Onboard NeoPixel (DevKitC V1.1) |
+| 43 | USB Console TX | UART0 | CH343 USB-serial (untouched) |
+| 44 | USB Console RX | UART0 | CH343 USB-serial (untouched) |
+
 ## Loopback Test (no dish)
 
 Before connecting to the G2, verify the bridge by shorting MAX485₁ A to