Transports

RadioKit supports multiple transport layers that can run simultaneously. The library broadcasts widget state changes across all active transports automatically.

BLE Transport

Bluetooth Low Energy via NimBLE-Arduino (ESP32).

RadioKit.startBLE("MyDevice");

Compile-time guard:

#define ENABLE_RK_BLE

When ENABLE_RK_BLE is defined, the generated setup() calls RadioKit.startBLE(). Comment out the define to disable BLE at compile time.

Configuration:

Setting	Default	Description
Service UUID	0000FFE0-0000-1000-8000-00805F9B34FB	BLE service identifier
Characteristic UUID	0000FFE1-0000-1000-8000-00805F9B34FB	BLE characteristic identifier
MTU	Auto-negotiated	Maximum transmission unit
Advertising name	RK_<device_name>	Auto-prefixed with RK_ for app filtering

Requirements:

• NimBLE-Arduino library (^1.4.1)
• ESP32 board (ESP32, ESP32-S3, ESP32-C3)

NVS Control:

BLE can be enabled/disabled via NVS. On first boot, BLE is enabled by default (rk_ble_on=1). The app can toggle this via the Settings protocol.

Serial Transport

USB/UART serial communication. Serial is always enabled by default — the generated code includes #define ENABLE_RK_SERIAL unconditionally. Comment out the define to disable serial.

RadioKit.startSerial(Serial);

Compile-time guard:

#define ENABLE_RK_SERIAL  // always defined by default

Configuration:

Setting	Default	Description
Baud Rate	1000000	Recommended for best performance
Data Bits	8	Standard serial configuration
Stop Bits	1	Standard serial configuration
Parity	None	Standard serial configuration

Supported Interfaces:

• USB CDC (native USB)
• FTDI FT232R
• CP2102/CP2104
• CH340/CH341
• Hardware UART

Auth Bypass: Physical serial access implies full device-level authentication. No password prompt is required.

WiFi Transport

WebSocket server on port 5555. Supports both AP and STA modes.

RadioKit.startWiFi();

Compile-time guard:

#define ENABLE_RK_WIFI

When ENABLE_RK_WIFI is defined, the generated setup() calls RadioKit.startWiFi(). Comment out the define to disable WiFi at compile time.

Configuration:

Setting	Default	Description
Port	5555	WebSocket server port
AP SSID	RK_<device_name>	Open network (no password)
STA SSID	Configured via config.sta_ssid or NVS	WiFi network name
STA Password	Configured via config.sta_password or NVS	WiFi network password

AP vs STA Mode:

• If sta_ssid is empty (default), the device starts in AP mode — creates an open WiFi network named RK_<device_name> that the phone connects to directly.
• If sta_ssid is configured (via config.sta_ssid or NVS), the device starts in STA mode — connects to the configured WiFi network. The phone must be on the same network.

NVS Persistence:

WiFi credentials are stored in NVS and survive power cycles. The app can update them via the SET_WIFI settings command (which triggers an automatic reboot to apply).

NVS Control:

WiFi can be enabled/disabled via NVS (rk_wifi_on). On first boot, WiFi is enabled by default.

Cloud Transport

WebSocket client connecting to a relay server. Requires WiFi to be active first.

RadioKit.config.cloud_url = "wss://relay.example.com:443";
RadioKit.config.cloud_account = "<public-key-hex>";
RadioKit.startCloud();  // Must call startWiFi() first

Compile-time guard:

#define ENABLE_RK_CLOUD

When ENABLE_RK_CLOUD is defined, the generated setup() calls RadioKit.startCloud(). Comment out the define to disable Cloud at compile time.

Configuration:

Setting	Default	Description
cloud_url	""	Relay server WebSocket URL
cloud_account	""	Ed25519 public key hex for authentication

Authentication:

Cloud relay uses Ed25519 challenge-response authentication. The cloud_account is the hex-encoded Ed25519 public key. The device signs a nonce from the relay server to prove identity.

NVS Persistence:

Cloud URL and account are stored in NVS. The app can update them via the SET_CLOUD_INFO settings command.

NVS Control:

Cloud can be enabled/disabled via NVS (rk_cloud_on). On first boot, Cloud is disabled by default. Cloud requires WiFi to be active — if WiFi is disabled, Cloud is suppressed even if rk_cloud_on=1.

Multiple Transports

You can activate multiple transports simultaneously. The designer generates #define directives at the top of the header file to enable/disable each transport at compile time:

#define ENABLE_RK_SERIAL
#define ENABLE_RK_BLE
#define ENABLE_RK_WIFI
// #define ENABLE_RK_CLOUD  // disabled

The generated setup() uses #ifdef guards around each start call:

void setup() {
  RadioKit.begin();
#ifdef ENABLE_RK_SERIAL
  RadioKit.startSerial(Serial);
#endif
#ifdef ENABLE_RK_BLE
  RadioKit.startBLE(RadioKit.config.name);
#endif
#ifdef ENABLE_RK_WIFI
  RadioKit.startWiFi();
#endif
#ifdef ENABLE_RK_CLOUD
  RadioKit.startCloud();  // Requires startWiFi() first
#endif
}

Serial is always defined by default. Comment out #define ENABLE_RK_SERIAL manually to disable serial.

The library will automatically broadcast widget state changes to all active transports.

Transport Status

Check transport status in your loop:

void loop() {
  RadioKit.update();

  if (RadioKit.isConnected()) {
    // At least one transport is connected
  }

  if (RadioKit.getRssi() != 0) {
    // BLE signal strength available
  }
}

Transport Enable/Disable via NVS

On first boot, the library writes default enable flags to NVS:

NVS Key	Default	Description
rk_ble_on	1	BLE transport enabled
rk_wifi_on	1	WiFi transport enabled
rk_cloud_on	0	Cloud transport disabled

The app can toggle these via the Settings protocol. Changes take effect on the next startBLE() / startWiFi() / startCloud() call (after reboot).