Ryan Malloy
068f38d7eb
NimBLE-based Nordic UART Service (NUS) bridge on ESP32-S3-DevKitC-1. Transparent passthrough: BLE client writes → UART1 TX → RS-422 → G2, and G2 → RS-422 → UART1 RX → BLE notifications. USB serial serves as debug monitor and fallback input. Uses two MAX485 modules (one locked TX, one locked RX) with a SparkFun BSS138 level converter for 3.3V/5V translation. Wiring schematic and RJ-12 pinout documented in docs/ble-bridge-wiring.md.
121 lines
6.4 KiB
Markdown
121 lines
6.4 KiB
Markdown
# BLE Bridge Wiring — ESP32-S3 + 2× MAX485
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Transparent BLE-to-RS422 bridge for the Winegard Carryout G2 satellite dish.
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## Parts
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- ESP32-S3-DevKitC-1-N16R8
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- 2× MAX485 TTL-to-RS485 module
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- 1× SparkFun Bidirectional Logic Level Converter (BOB-12009, BSS138-based)
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- RJ-12 6P6C straight-wired cable with breakout
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- Hookup wire / jumpers
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## Schematic
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```
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SparkFun Level Converter (BOB-12009)
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┌──────────────────────────────────────┐
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│ │
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ESP32 3V3 ──────────────►│ LV HV │◄── ESP32 5V
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ESP32 GND ──────────────►│ GND GND │◄── (shared)
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│ │
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ESP32 GPIO17 (TX) ──────►│ LV1 HV1 │──────► MAX485₁ DI
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ESP32 GPIO18 (RX) ◄──────│ LV2 HV2 │◄────── MAX485₂ RO
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│ │
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│ LV3 (spare) HV3 (spare) │
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│ LV4 (spare) HV4 (spare) │
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└──────────────────────────────────────┘
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MAX485 Board 1 (TX only) MAX485 Board 2 (RX only)
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┌────────────────────────┐ ┌────────────────────────┐
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│ VCC ◄── 5V │ │ VCC ◄── 5V │
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│ GND ◄── GND │ │ GND ◄── GND │
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│ │ │ │
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│ DI ◄── HV1 │ │ RO ──► HV2 │
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│ RO (unused) │ │ DI (unused) │
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│ │ │ │
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│ DE ◄── 5V ┐ locked │ │ DE ◄── GND ┐ locked │
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│ RE ◄── 5V ┘ TX mode │ │ RE ◄── GND ┘ RX mode │
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│ │ │ │
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│ A ───────────────────┼──► pin 2 │ A ◄──────────────────┼── pin 4
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│ B ───────────────────┼──► pin 3 │ B ◄──────────────────┼── pin 5
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└────────────────────────┘ └────────────────────────┘
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RJ-12 to Carryout G2
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┌───────────────────────────┐
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│ Pin 1 (White) ── GND │◄── ESP32 GND
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│ Pin 2 (Red) ── TX+/TA │◄── A₁
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│ Pin 3 (Black) ── TX-/TB │◄── B₁
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│ Pin 4 (Yellow) ── RX+/RA │──► A₂
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│ Pin 5 (Green) ── RX-/RB │──► B₂
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│ Pin 6 (Blue) ── N/C │
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└───────────────────────────┘
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```
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## Power Rails
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```
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ESP32 5V ──┬── Level Converter HV
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├── MAX485₁ VCC
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├── MAX485₁ DE + RE (tied high = TX mode)
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└── MAX485₂ VCC
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ESP32 3V3 ─── Level Converter LV
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ESP32 GND ─┬── Level Converter GND
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├── MAX485₁ GND
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├── MAX485₂ GND
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├── MAX485₂ DE + RE (tied low = RX mode)
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└── RJ-12 Pin 1
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```
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## RJ-12 Cable Notes
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Straight-wired 6P6C. Pin 1 is leftmost when looking at the jack with the clip
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facing away from you (tab down). Wire colors per the standard flat cable:
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| Pin | Color | Function | Connects to |
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|-----|--------|------------------|--------------------|
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| 1 | White | GND | Common ground |
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| 2 | Red | TX+ (TA) | MAX485₁ A |
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| 3 | Black | TX- (TB) | MAX485₁ B |
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| 4 | Yellow | RX+ (RA) | MAX485₂ A |
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| 5 | Green | RX- (RB) | MAX485₂ B |
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| 6 | Blue | N/C | — |
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If crimping your own cable, verify pin-to-color with a multimeter before
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connecting to the dish. RJ-12 crimps are easy to get reversed (pins mirror
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if the connector is flipped). A wrong connection won't damage anything
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(differential signals are current-limited) but communication won't work.
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## How It Works
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The Carryout G2 uses RS-422 full-duplex: two separate differential pairs,
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one for each direction. The MAX485 is a half-duplex RS-485 transceiver with
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a shared A/B pair and direction control pins (DE/RE). By hardwiring DE/RE,
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each board is locked into a single direction:
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- **Board 1 (TX):** DE=HIGH, RE=HIGH → driver always enabled, receiver disabled.
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ESP32 UART1 TX → level shifter → DI → differential A/B → G2 serial RX.
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- **Board 2 (RX):** DE=LOW, RE=LOW → driver disabled, receiver always enabled.
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G2 serial TX → differential A/B → RO → level shifter → ESP32 UART1 RX.
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The SparkFun level converter translates between 3.3V (ESP32) and 5V (MAX485)
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on both data lines. The two spare channels (LV3/HV3, LV4/HV4) are available
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if DE/RE ever need GPIO control for a half-duplex variant.
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## Firmware
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See `firmware/ble-bridge/` — transparent BLE Nordic UART Service (NUS) bridge.
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The firmware is the same regardless of whether the RS-422 transceiver is a
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MAX490 (single full-duplex chip) or two MAX485s (locked half-duplex pair).
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It only sees UART TX/RX on GPIO17/18.
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## Loopback Test (no dish)
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Before connecting to the G2, verify the bridge by shorting MAX485₁ A to
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MAX485₂ A, and MAX485₁ B to MAX485₂ B (loop TX back into RX). Anything
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sent via BLE or USB serial should echo back.
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