Arduino

#include <bluefruit.h>
 
// Custom 128-bit UUIDs (change these to whatever you want)
BLEService customService(BLEUuid("12345678-1234-5678-1234-56789abcdef2"));
BLECharacteristic customChar(BLEUuid("12345678-1234-5678-1234-56789abcdef3"));
 
uint8_t value = 0;
 
void setup() {
  Serial.begin(115200);
  while (!Serial) { delay(10); }  // for nRF52840 with native USB
 
  Serial.println("Simple custom BLE example");
 
  Bluefruit.begin();
  Bluefruit.setName("Bleboard");
 
  customService.begin();
 
  customChar.setProperties(CHR_PROPS_READ | CHR_PROPS_NOTIFY);
  customChar.setPermission(SECMODE_OPEN, SECMODE_OPEN);
  customChar.setFixedLen(1);
  customChar.begin();
 
  // Set the initial characteristic value so reads return value
  customChar.write8(value);
 
  Bluefruit.Advertising.addService(customService);
  Bluefruit.Advertising.start(0);
 
  Serial.println("Advertising...");
}
 
void loop() {
  static uint32_t lastNotifyMs = 0;
  uint32_t now = millis();
 
  // Notify once per second if a central is connected
  if (Bluefruit.connected() && (now - lastNotifyMs) > 1000) {
    lastNotifyMs = now;
    value++;
 
    // Keep it in range
    if (value >= 100) {
      value = 0;
    }
 
    // Update characteristic value
    customChar.write8(value);
 
    // Send notification (only delivered if central enabled notifications)
    customChar.notify8(value);
 
    Serial.print("Notified value: ");
    Serial.println(value);
  }
  delay(1000);
}