BLE ESP32 Comm

Cross-platform BLE code example that demonstrates how to connect an iPhone or Android phone to an ESP32 using Bluetooth Low Energy. It shows a simple read/write flow by exchanging a single 32-bit integer and persisting that value on the ESP32 so it survives power cycles.

Includes:

• A SwiftUI iOS app that scans for an ESP32 peripheral, reads/writes a 32-bit value over BLE, and listens for notifications.
• An ESP32 firmware project that builds in both Arduino IDE and PlatformIO (shared source).
• Android clients (Compose + legacy Views) for parity testing.

Notes:

• You can only connect one device to the ESP32 at a time. Tap the "Disconnect" button on the currently connected device if you want to try it on a separate device.
• You can use the legacy Android build, but it's not being maintained or updated. The Jetpack Compose version is.
• Both Arduino IDE and PlatformIO reference the same .cpp file at esp32-firmware/shared/BLEMemoryBridge.cpp

Compatibility

• Firmware: ESP32 Arduino core 3.x (Arduino IDE) or PlatformIO espressif32 platform.
• Clients: iOS physical device (BLE required), Android 13+ physical device (BLE required).

Known Issues

• ESP32 upload via PlatformIO can fail to connect; hold BOOT/IO0 or tap EN/RESET when “Connecting...” appears.

Project Structure

• BLE-ESPCom/ — iOS app. Open BLE-ESPCom/BLE-ESPCom.xcodeproj in Xcode. Sources live in BLE-ESPCom/BLE-ESPCom/ (ContentView.swift, BLEManager.swift, BLE_ESPComApp.swift). Assets in Assets.xcassets/.
• BLE-ESP32ComAndroid/ — Legacy Android (Views). Open in Android Studio. Layouts in app/src/main/res/layout/ (activity_main.xml, content_main.xml, drawable/status_dot.xml); logic in app/src/main/java/com/skyeroad/ble_esp32com/MainActivity.kt.
• BLEESP32ComJPC/ — Jetpack Compose Android app (Material 3, iOS-like palette). Entry: app/src/main/java/com/skyeroad/ble_esp32comjpc/MainActivity.kt; BLE logic in ble/BleClient.kt + BleViewModel.kt. MinSdk 33, targetSdk 36. Build with ./gradlew :app:assembleDebug.
• esp32-firmware/ — ESP32 firmware with shared sources for Arduino IDE + PlatformIO. See esp32-firmware/README.md.

Screenshots

SwiftUI Screenshot	Jetpack Compose Screenshot

BLE Contract (shared IDs)

• Service UUID: d973f2b9-2ed7-4d5b-ad07-4d1974f2c925
• Characteristic UUID: d973f2b9-2ed7-4d5b-ad07-4d1974f2c926
• Data: 32-bit unsigned integer, little-endian. Notifications sent after writes.

Running the iOS App

1. Open BLE-ESPCom/BLE-ESPCom.xcodeproj in Xcode.
2. Build/run on a physical device (BLE is not available in the simulator) — ⌘R.
3. Tap Scan to find the ESP32 (ESP32 Memory Bridge), connect, then Read or enter a value and Write.

Running the Android Apps

• Compose app (recommended): open BLEESP32ComJPC/ in Android Studio or run ./gradlew :app:assembleDebug. Use a physical device (BLE not available on the emulator), MinSdk 33. Main screen mirrors the iOS layout: status dot + state, Scan/Disconnect row, “Last value” card, numeric input + Write/Read buttons. BLE filtering by service UUID; notifications update the last value text.
• Legacy views app: open BLE-ESP32ComAndroid/ if you need the original XML-based UI. Physical device required; same BLE behavior and UUIDs.

ESP32 Firmware (Arduino IDE + PlatformIO)

The firmware is a shared codebase located in esp32-firmware/shared/ with thin entry points for each build system.

Arduino IDE

1. Open esp32-firmware/arduino/BLEMemoryBridge/BLEMemoryBridge.ino in Arduino IDE.
2. Select your ESP32 board and port, then Upload.
3. Defaults to value 0x12345678, persisted to NVS; re-advertises automatically after disconnects.

PlatformIO

1. Open esp32-firmware/platformio/ in PlatformIO.
2. Build: pio run
3. Upload: pio run -t upload
4. Serial monitor: pio device monitor -b 115200

If upload fails to connect, hold the BOOT/IO0 button while the upload begins or tap EN/RESET when you see “Connecting...”. If PlatformIO picks the wrong port, pass it explicitly, for example: pio run -t upload --upload-port /dev/cu.usbserial-0001.

Notes

• Keep UUIDs in sync if you change them in either side.
• Use a BLE explorer (nRF Connect, LightBlue) for quick validation.
• ESP32 default firmware supports a single central at a time; allowing multiple centrals would require increasing NimBLE connection limits on the firmware and validating memory/performance.