Calculate BER of BLE

[youssefelbattah]

Hello,

I am attempting to calculate the Binary Error Rate (BER) of the Bluetooth Low Energy (BLE) protocol. When I send 20KB of data in chunks of 20 bytes, all data is received correctly (BER == 0). However, when I try to send data sizes between 21KB and 22KB (e.g., 21KB, 21.5KB), the central device fails to connect to my board, and the Arduino blocks. Interestingly, when I send 25KB, everything works fine again.

#include <ArduinoBLE.h>

#define LENGTH  21000  // Adjust LENGTH for testing

const char * deviceServiceUuid = "1523";
const char * deviceServiceRequestCharacteristicUuid = "1526";
const char * deviceServiceResponseCharacteristicUuid = "1527";

BLEService ArduinoMLXService(deviceServiceUuid);
BLECharacteristic ArduinoMLXRequestCharacteristic(deviceServiceRequestCharacteristicUuid, BLEWrite, 4);
BLECharacteristic ArduinoMLXResponseCharacteristic(deviceServiceResponseCharacteristicUuid, BLENotify, 20);

uint8_t *testSequence;

void setup() {
  Serial.begin(9600);
  while (!Serial);
  Serial.println("Starting BLE setup...");

  testSequence = (uint8_t*)malloc(LENGTH * sizeof(uint8_t));
  if (!testSequence) {
    Serial.println("Memory allocation failed!");
    while (1);
  }

  for(int i = 0; i < LENGTH; i++) {
    testSequence[i] = i % 256;
  }

  BLE.setDeviceName("ArduinoMLX");
  BLE.setLocalName("ArduinoMLX");

  if (!BLE.begin()) {
    Serial.println(F("Starting BLE module failed!"));
    while (1);
  }

  BLE.setAdvertisedService(ArduinoMLXService);
  ArduinoMLXService.addCharacteristic(ArduinoMLXRequestCharacteristic);
  ArduinoMLXService.addCharacteristic(ArduinoMLXResponseCharacteristic);
  BLE.addService(ArduinoMLXService);
  BLE.advertise();
  Serial.println("BLE setup done.");
}

void loop() {
  BLEDevice central = BLE.central();
  Serial.println("searching..");
  if (central) {
    Serial.println("CENTRAL..");
    Serial.print("Connected to ");
    Serial.println(central.address());
    while (central.connected()) {
      BLE.poll();
      sendLargeDataOverBLE(LENGTH, testSequence);
      delay(3000);
    }
    Serial.print("Disconnected from ");
    Serial.println(central.address());
  }
}

void sendLargeDataOverBLE(size_t size, uint8_t *data_to_send) {
  for (int i = 0; i < size; i += 20) {
    uint8_t chunk[20];
    int chunkSize = min(20, size - i);
    memcpy(chunk, data_to_send + i, chunkSize);
    ArduinoMLXResponseCharacteristic.writeValue(chunk, chunkSize);
    // Delay is commented out, uncomment if needed for stability
    // delay(10);
  }
  Serial.println("All data is sent");
}