# BLE Bridge Wiring — ESP32-S3 + 2× MAX485

Transparent BLE-to-RS422 bridge for the Winegard Carryout G2 satellite dish.

## Parts

- 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

## Schematic

```
                          SparkFun Level Converter (BOB-12009)
                         ┌──────────────────────────────────────┐
                         │                                      │
ESP32 3V3 ──────────────►│ LV                            HV │◄── ESP32 5V
ESP32 GND ──────────────►│ GND                          GND │◄── (shared)
                         │                                      │
ESP32 GPIO17 (TX) ──────►│ LV1                          HV1 │──────► MAX485₁ DI
ESP32 GPIO18 (RX) ◄──────│ LV2                          HV2 │◄────── MAX485₂ RO
                         │                                      │
                         │  LV3  (spare)          HV3  (spare)  │
                         │  LV4  (spare)          HV4  (spare)  │
                         └──────────────────────────────────────┘


    MAX485 Board 1 (TX only)              MAX485 Board 2 (RX only)
    ┌────────────────────────┐            ┌────────────────────────┐
    │  VCC ◄── 5V            │            │  VCC ◄── 5V            │
    │  GND ◄── GND           │            │  GND ◄── GND           │
    │                        │            │                        │
    │  DI  ◄── HV1           │            │  RO  ──► HV2           │
    │  RO     (unused)       │            │  DI     (unused)       │
    │                        │            │                        │
    │  DE  ◄── 5V ┐ locked   │            │  DE  ◄── GND ┐ locked  │
    │  RE  ◄── 5V ┘ TX mode  │            │  RE  ◄── GND ┘ RX mode │
    │                        │            │                        │
    │  A  ───────────────────┼──► pin 2   │  A  ◄──────────────────┼── pin 4
    │  B  ───────────────────┼──► pin 3   │  B  ◄──────────────────┼── pin 5
    └────────────────────────┘            └────────────────────────┘

                        RJ-12 to Carryout G2
                    ┌───────────────────────────┐
                    │  Pin 1 (White)  ── GND     │◄── ESP32 GND
                    │  Pin 2 (Red)    ── TX+/TA  │◄── A₁
                    │  Pin 3 (Black)  ── TX-/TB  │◄── B₁
                    │  Pin 4 (Yellow) ── RX+/RA  │──► A₂
                    │  Pin 5 (Green)  ── RX-/RB  │──► B₂
                    │  Pin 6 (Blue)   ── N/C     │
                    └───────────────────────────┘
```

## Power Rails

```
ESP32 5V ──┬── Level Converter HV
           ├── MAX485₁ VCC
           ├── MAX485₁ DE + RE (tied high = TX mode)
           └── MAX485₂ VCC

ESP32 3V3 ─── Level Converter LV

ESP32 GND ─┬── Level Converter GND
           ├── MAX485₁ GND
           ├── MAX485₂ GND
           ├── MAX485₂ DE + RE (tied low = RX mode)
           └── RJ-12 Pin 1
```

## RJ-12 Cable Notes

Straight-wired 6P6C. Pin 1 is leftmost when looking at the jack with the clip
facing away from you (tab down). Wire colors per the standard flat cable:

| Pin | Color  | Function         | Connects to       |
|-----|--------|------------------|--------------------|
| 1   | White  | GND              | Common ground      |
| 2   | Red    | TX+ (TA)         | MAX485₁ A          |
| 3   | Black  | TX- (TB)         | MAX485₁ B          |
| 4   | Yellow | RX+ (RA)         | MAX485₂ A          |
| 5   | Green  | RX- (RB)         | MAX485₂ B          |
| 6   | Blue   | N/C              | —                  |

If crimping your own cable, verify pin-to-color with a multimeter before
connecting to the dish. RJ-12 crimps are easy to get reversed (pins mirror
if the connector is flipped). A wrong connection won't damage anything
(differential signals are current-limited) but communication won't work.

## How It Works

The Carryout G2 uses RS-422 full-duplex: two separate differential pairs,
one for each direction. The MAX485 is a half-duplex RS-485 transceiver with
a shared A/B pair and direction control pins (DE/RE). By hardwiring DE/RE,
each board is locked into a single direction:

- **Board 1 (TX):** DE=HIGH, RE=HIGH → driver always enabled, receiver disabled.
  ESP32 UART1 TX → level shifter → DI → differential A/B → G2 serial RX.

- **Board 2 (RX):** DE=LOW, RE=LOW → driver disabled, receiver always enabled.
  G2 serial TX → differential A/B → RO → level shifter → ESP32 UART1 RX.

The SparkFun level converter translates between 3.3V (ESP32) and 5V (MAX485)
on both data lines. The two spare channels (LV3/HV3, LV4/HV4) are available
if DE/RE ever need GPIO control for a half-duplex variant.

## Firmware

See `firmware/ble-bridge/` — transparent BLE Nordic UART Service (NUS) bridge.
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.

## Loopback Test (no dish)

Before connecting to the G2, verify the bridge by shorting MAX485₁ A to
MAX485₂ A, and MAX485₁ B to MAX485₂ B (loop TX back into RX). Anything
sent via BLE or USB serial should echo back.