Ryan Malloy 068f38d7eb Add ESP32-S3 BLE-to-RS422 bridge firmware for Carryout G2

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.

2026-02-11 14:33:10 -07:00

6.4 KiB

Raw Blame History

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.

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