Arduino

// Adafruit Bluefruit nRF52 (e.g. Feather nRF52832 / nRF52840)
#include <bluefruit.h>
 
// BLEUart implements Nordic UART Service (NUS):
// Service 6E400001-..., RX 6E400002-... (central->peripheral), TX 6E400003-... (peripheral->central)
BLEUart bleuart;
 
void setup()
{
  Serial.begin(115200);
 
  Bluefruit.begin();
  Bluefruit.setName("Arduino-NUS");
  Bluefruit.configPrphBandwidth(BANDWIDTH_MAX);
 
  bleuart.begin();
 
  // Advertise NUS so scanners can find it
  Bluefruit.Advertising.addFlags(BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE);
  Bluefruit.Advertising.addTxPower();
  Bluefruit.Advertising.addService(bleuart);
  Bluefruit.ScanResponse.addName();
  Bluefruit.Advertising.restartOnDisconnect(true);
  Bluefruit.Advertising.setInterval(32, 244);
  Bluefruit.Advertising.start(0);
}
 
void loop()
{
  // Forward data from central (NUS RX) to Serial — like onNusRx
  while (bleuart.available())
  {
    uint8_t buf[64];
    int count = bleuart.read(buf, sizeof(buf));
    if (count > 0)
    {
      Serial.print("NUS RX (");
      Serial.print(count);
      Serial.print(" bytes): ");
      Serial.write(buf, count);
      Serial.println();
    }
  }
 
  // Every 1s when connected, send a line on NUS TX (notify)
  static unsigned long last = 0;
  if (millis() - last >= 1000)
  {
    last = millis();
    if (Bluefruit.connected())
    {
      bleuart.print("hello from Arduino over NUS\n");
    }
  }
}