Add Bluetooth telemetry (S.Port + CRSF), auto-connect and a selectable NimBLE host

README.md

@@ -1,7 +1,99 @@
 # BTWifiModule
-Frsky Bluetooth Emulator
 
-This code is for use on a ESP Wroom 32, it emulates a FRSky Bluetooth module but with way more future possibilities.
+FrSky Bluetooth emulator for ESP32, to be used inside an OpenTX/EdgeTX radio.
+It emulates a FrSky Bluetooth module and adds **Bluetooth telemetry**
+(S.Port and CRSF), **auto-connect** and a **selectable BLE host**
+(Bluedroid or NimBLE).
 
-## Documentation for this project is at Git Book
-### https://btwifimod.gitbook.io/
+Based on the community project by **dlktdr**
+(https://github.com/dlktdr/BTWifiModule).
+Documentation: https://btwifimod.gitbook.io/
+
+## Features
+
+| Feature | Status |
+|---|---|
+| Bluetooth Trainer — Master Mode (connect to a BLE trainer / headtracker) | Supported |
+| Bluetooth Trainer — Slave Mode | Supported |
+| Bluetooth Telemetry over BLE | Supported |
+| — S.Port (FrSky models) | Supported |
+| — CRSF (ELRS models) | Supported |
+| Auto-connect to the last known device | Supported |
+| Device name from `AT+NAME` (persisted and advertised) | Supported |
+| Selectable BLE host: Bluedroid or NimBLE | Supported |
+
+## How telemetry works
+
+In *Telemetry* mode EdgeTX forwards the radio's telemetry over the BT serial
+link. The module passes those bytes to the connected BLE central unchanged:
+
+- FrSky models: S.Port frames, `0x7E`-delimited and byte-stuffed.
+- ELRS/CRSF models: raw CRSF frames.
+
+The client app auto-detects the protocol, so both work over the same GATT
+service (`0xFFF0`, characteristic `0xFFF6`, NOTIFY).
+
+## Telemetry app
+
+- S.Port: **INAV / Telemetry Viewer**.
+- CRSF: the maintained fork by **RomanLut**
+  (https://github.com/RomanLut/android-taranis-smartport-telemetry/releases),
+  which publishes ready-made APKs with CRSF support.
+
+## Hardware
+
+- **ESP32-C3 SuperMini** (primary target); other boards are listed in
+  `platformio.ini`.
+- UART to the radio: **GPIO20 (RX) / GPIO21 (TX)** on the C3 SuperMini.
+- **Radiomaster TX16S MK3** with **EdgeTX** (a recent nightly is recommended,
+  see below).
+
+> **TX16S MK3 note.** EdgeTX needs PR #7855
+> (`BT_PWR_GPIO = PC13` in `targets/tx16smk3/hal.h`) to power the AUX2/BT
+> connector. It is included in current nightlies.
+
+## Building
+
+PlatformIO (ESP-IDF). Two BLE hosts are selectable:
+
+| Environment | BLE host | Flash (C3, 1 MB app) | Notes |
+|---|---|---|---|
+| `C3SuperMini` | Bluedroid (default) | ~84 % | |
+| `C3SuperMini_nimble` | NimBLE | ~52 % | smaller footprint, recommended |
+
+```bash
+pio run -e C3SuperMini -t upload          # Bluedroid
+pio run -e C3SuperMini_nimble -t upload   # NimBLE
+```
+
+The Bluedroid path is kept behind `#if !defined(USE_NIMBLE)`, so both hosts
+share the same application code.
+
+## AT command set
+
+The module speaks the same AT protocol EdgeTX uses for the FrSky Bluetooth
+module:
+
+| Command | Meaning |
+|---|---|
+| `AT+BAUD4` | baud rate (this firmware stays at 115200) |
+| `AT+NAME<name>` | set the Bluetooth name (persisted and advertised) |
+| `AT+TXPW<n>` | TX power (acknowledged) |
+| `AT+ROLE0` | Peripheral (telemetry / trainer slave) |
+| `AT+ROLE1` | Central (trainer master) |
+| `AT+DISC?` | start a scan (central) |
+| `AT+CON<addr>` | connect to a device (central) |
+| `AT+CLEAR` | forget the saved device |
+| `AT+HTRESET` | reset the headtracker (BTWifiModule extension) |
+
+Responses: `OK+...`, `Central:<addr>`, `Peripheral:<addr>`, `Connected:<addr>`,
+`DisConnected`, `ERROR`.
+
+## Branches
+
+- `1.0-dev` — consolidated development branch (this one).
+
+## Credits
+
+Original project: **dlktdr/BTWifiModule**. Bluetooth telemetry, auto-connect,
+the CRSF passthrough and the NimBLE port by this fork.

platformio.ini

@@ -9,10 +9,10 @@
 ; https://docs.platformio.org/page/projectconf.html
 
 [platformio]
-default_envs = C3Mini
+default_envs = C3SuperMini
 
 [env]
-platform = espressif32
+platform = espressif32@6.7.0
 framework = espidf
 build_unflags = -Werror=all
 
@@ -131,3 +131,21 @@ build_flags =
     -DCPU_ESP32=y
     -DBLUETOOTH=y
     -DBLUETOOTH5=y
+
+; NimBLE experiment build (same board, NimBLE host instead of Bluedroid)
+[env:C3SuperMini_nimble]
+board_build.flash_mode: dio
+board = esp32-c3-devkitm-1
+board_build.esp-idf.sdkconfig_path = sdkconfig.C3SuperMini_nimble
+upload_protocol = esptool
+build_type = debug
+monitor_speed = 115200
+upload_port = COM9
+monitor_port = COM9
+build_flags =
+    -DRTOS_FREERTOS=y
+    -DPCB_C3SUPERMINI=y
+    -DCPU_ESP32=y
+    -DBLUETOOTH=y
+    -DBLUETOOTH5=y
+    -DUSE_NIMBLE=y