ESP32 BLE Scan Finds No Devices

In this tutorial, you'll learn about ESP32 BLE Scan Finds No Devices. We cover key concepts, practical examples, and best practices.

The Problem

ESP32 BLE central scan returns 0 results even when BLE devices are nearby.

Quick Fix

Wrong

BLEScan* pScan = BLEDevice::getScan();
pScan->start(10);

Scan results: 0 devices found

Right

BLEScan* pScan = BLEDevice::getScan();
pScan->setActiveScan(true);
pScan->setInterval(100);
pScan->setWindow(99);
BLEScanResults results = pScan->start(10, false);
Serial.printf("Found %d devices
", results.getCount());
for (int i = 0; i < results.getCount(); i++) {
  Serial.printf("%s (%d dBm)
", results.getDevice(i).toString().c_str(), results.getDevice(i).getRSSI());
}

Found 4 devices:
BLE-Sensor (1c:23:45:67:89:ab) -52 dBm
SmartBand (ab:cd:ef:12:34:56) -61 dBm

Prevention

Set active scan to true for complete device information. Configure scan interval (100-1000 ms) and window (less than interval). Pass false for second parameter of start() to block until complete. Register a scan callback for async results. Scan for at least 5 seconds.

DodaTech engineers apply these same patterns when building Doda Browser's networking stack, DodaZIP's firmware packaging pipeline, and Durga Antivirus Pro's sensor communication layer.

FAQ