# SAUL-TEE Wiring Reference

**Authoritative reference:** [`docs/SAUL-TEE-SYSTEM-REFERENCE.md`](SAUL-TEE-SYSTEM-REFERENCE.md)

This document is a quick-access wiring summary. For pin assignments, CAN frame formats,
RC channel mapping, and serial commands, see the full reference doc.

---

## System Block Diagram

```
                    ┌──────────────────────────────────────────────────────────┐
                    │               JETSON ORIN NANO SUPER                     │
                    │                  (Top plate, 25W)                        │
                    │                                                          │
                    │  USB-A ──── CANable 2.0 USB↔CAN (can0, 500 kbps)       │
                    │  USB-A ──── RealSense D435i (USB 3.1)                  │
                    │  USB-A ──── RPLIDAR A1M8 (CP2102, 115200)              │
                    │  USB-C ──── SIM7600A 4G/LTE modem                      │
                    │  CSI-A ─── 2× IMX219 cameras (front + left)            │
                    │  CSI-B ─── 2× IMX219 cameras (rear + right)            │
                    │  40-pin ── ReSpeaker 2-Mic HAT                          │
                    └──────────────────────┬───────────────────────────────────┘
                                           │ USB-A → CANable 2.0
                                           │ can0, 500 kbps
          ┌────────────────────────────────┴──────────────────────────────────┐
          │                    CAN BUS  (CANH / CANL / GND)                   │
          │              120 Ω ─┤                     ├─ 120 Ω               │
          └───────────┬──────────────────────────────────────────┬────────────┘
                      │                                          │
          ┌───────────┴────────────┐              ┌─────────────┴──────────┐
          │  ESP32-S3 BALANCE      │              │  VESC left  (ID 68)    │
          │  Waveshare Touch LCD   │              │  VESC right (ID 56)    │
          │  1.28 — CH343 USB      │              │  FSESC 6.7 Pro Mini    │
          │                        │              │  Dual                  │
          │  QMI8658 IMU (I2C)     │              └──────┬─────────────────┘
          │  SN65HVD230 (CAN)      │                     │ Phase wires
          │                        │            ┌────────┴─────────────┐
          │  UART ──────────────┐  │            │  Hub motors (4×)     │
          └────────────────────────┘            │  FL / FR / RL / RR   │
            ↕ 460800 baud binary │              └──────────────────────┘
              inter-board proto  │
          ┌───────────────────────┘
          │  ESP32-S3 IO (bare board)
          │  JTAG USB
          │
          │  UART0 ── TBS Crossfire RX (CRSF @ 420000)
          │  UART2 ── ELRS receiver (CRSF failover @ 420000)
          │  PWM ──── 4× BTS7960 H-bridge motor drivers
          │  I2C ──── NFC + Barometer + ToF (shared bus)
          │  RMT ──── WS2812B LED strip
          │  GPIO ─── Horn / Headlight / Fan / Buzzer
          └──────────────────────────────────────────────
```

---

## Wire-by-Wire Connections

### 1. Orin ↔ CAN Bus (via CANable 2.0)

| From | To | Notes |
|------|----|-------|
| Orin USB-A | CANable 2.0 USB | `/dev/canable0` → `can0` |
| CANable CANH | CAN bus CANH | Twisted pair |
| CANable CANL | CAN bus CANL | Twisted pair |
| CANable GND | CAN GND | Common |

Setup: `ip link set can0 up type can bitrate 500000`

### 2. ESP32-S3 BALANCE ↔ CAN Bus

| Signal | GPIO | CAN bus |
|--------|------|---------|
| CAN TX | TBD | → SN65HVD230 D pin |
| CAN RX | TBD | ← SN65HVD230 R pin |

> TBD pins — confirm in `esp32/balance/src/config.h`

### 3. ESP32-S3 BALANCE ↔ ESP32-S3 IO (Inter-Board UART)

| Signal | BALANCE GPIO | IO GPIO | Baud |
|--------|-------------|---------|------|
| TX | TBD | TBD (RX) | 460800 |
| RX | TBD (RX) | TBD (TX) | 460800 |
| GND | GND | GND | — |

Frame: `[0xAA][LEN][TYPE][PAYLOAD…][CRC8]` — see `esp32/shared/protocol.h`

### 4. ESP32-S3 IO ↔ TBS Crossfire RX (UART0)

| IO GPIO | Signal | Crossfire pin | Notes |
|---------|--------|---------------|-------|
| GPIO43 | TX | RX | CRSF telemetry to TX module |
| GPIO44 | RX | TX | CRSF RC frames in |
| GND | GND | GND | |
| 5V | — | VCC | Power from 5V bus |

Baud: 420000 (CRSF). Failsafe: disarm after 300 ms without frame.

### 5. ESP32-S3 IO ↔ ELRS Receiver (UART2, failover)

| IO GPIO | Signal | ELRS pin |
|---------|--------|----------|
| TBD | TX | RX |
| TBD | RX | TX |
| GND | GND | GND |
| 5V | — | VCC |

Baud: 420000 (CRSF). Activates automatically if Crossfire link lost >300 ms.

### 6. ESP32-S3 IO ↔ BTS7960 Motor Drivers (4×)

TBD GPIO assignments — see `esp32/io/src/config.h`.

| Signal | Per-driver | Notes |
|--------|-----------|-------|
| RPWM | GPIO TBD | Forward PWM |
| LPWM | GPIO TBD | Reverse PWM |
| R_EN | GPIO TBD | Enable H |
| L_EN | GPIO TBD | Enable H |
| Motor+ / Motor− | Hub motor | 36V via B+ / B− on BTS7960 |

### 7. ESP32-S3 IO I2C Sensors

| Device | I2C Address | Notes |
|--------|-------------|-------|
| NFC (PN532) | 0x24 | NFC tag read/write |
| Barometer (BMP280/388) | 0x76 | Altitude + temp |
| ToF range (VL53L0X) | 0x29 | Proximity/obstacle |

> SDA / SCL GPIOs TBD — confirm in `esp32/io/src/config.h`

### 8. Power Distribution

```
36V BATTERY
  │
  ├── VESC left  (36V) ─── Front-left + Rear-left hub motors
  ├── VESC right (36V) ─── Front-right + Rear-right hub motors
  ├── BTS7960 boards (B+/B−) — 36V motor power
  │
  ├── DC-DC 12V ──── Fan / Headlight / Accessories
  │
  └── DC-DC 5V ─┬── Jetson Orin (USB-C PD)
                 ├── ESP32-S3 BALANCE (USB 5V)
                 ├── ESP32-S3 IO (USB 5V)
                 ├── TBS Crossfire RX (5V)
                 ├── ELRS RX (5V)
                 ├── WS2812B strip (5V)
                 ├── RPLIDAR A1M8 (5V via USB)
                 └── Sensors (3.3V from ESP32-IO LDO)
```

---

## Orin USB Peripherals

| Device | Interface | Node |
|--------|-----------|------|
| CANable 2.0 | USB-A | `can0` (after `ip link set can0 up type can bitrate 500000`) |
| RealSense D435i | USB 3.1 | `/dev/bus/usb/...` |
| RPLIDAR A1M8 | USB-UART | `/dev/rplidar` |
| SIM7600A 4G | USB | `/dev/ttyUSB0–2` |
| ESP32-S3 BALANCE debug | USB-A (CH343) | `/dev/esp32-balance` |
| ESP32-S3 IO debug | USB-A (JTAG/CDC) | `/dev/esp32-io` |

---

## ReSpeaker 2-Mic HAT (Orin 40-pin)

| Orin Pin | Signal | Function |
|----------|--------|----------|
| Pin 12 (GPIO 18) | I2S BCLK | Audio bit clock |
| Pin 35 (GPIO 19) | I2S LRCLK | Audio left/right clock |
| Pin 38 (GPIO 20) | I2S DIN | Audio data in (from mics) |
| Pin 40 (GPIO 21) | I2S DOUT | Audio data out (to speaker) |
| Pin 3 (GPIO 2) | I2C SDA | WM8960 codec (i2c-7) |
| Pin 5 (GPIO 3) | I2C SCL | WM8960 codec (i2c-7) |
| Pin 2, 4 | 5V | Power |
| Pin 6, 9 | GND | Ground |

Codec: Wolfson WM8960 (0x1A). Use: voice commands, wake word, audio feedback.

---

## SIM7600A 4G/LTE HAT (Orin USB)

| Connection | Detail |
|-----------|--------|
| Interface | USB (micro-B on HAT → USB-A on Orin) |
| Device nodes | `/dev/ttyUSB0` (AT), `/dev/ttyUSB1` (PPP/data), `/dev/ttyUSB2` (GPS NMEA) |
| Power | 5V from USB (peak 2A during TX) |
| SIM | Nano-SIM slot |