ESP32 Eddystone URL Beacon (Deep Sleep Broadcasting)

Snippet summary:
This example shows how to turn an ESP32 into a BLE beacon that broadcasts Eddystone URL frames. It periodically advertises a compressed URL, rotates between multiple URLs across wake cycles, and uses deep sleep to achieve ultra-low power operation.

Introduction

• This example demonstrates BLE beacon broadcasting, not client/server communication
• The ESP32 advertises a URL over BLE using the Eddystone protocol
• No connections are required — devices simply scan and read the broadcast
• Designed for low-power IoT and proximity-based applications

👉 Think of it as a wireless URL broadcaster

What is Eddystone URL

• A BLE beacon format defined by Google
• Broadcasts compressed URLs inside BLE advertisements
• Designed for:

👉 Instead of pairing, devices just scan and decode the URL

What this example does

• Cycles through a list of predefined URLs
• Encodes each into Eddystone format
• Broadcasts it for 10 seconds
• Enters deep sleep
• Wakes up and broadcasts the next URL

👉 Each wake cycle = different URL

URL list and rotation

String URL[] = { ... }

• Contains multiple URLs
• Examples include:

Selection logic:

URL[bootcount % (sizeof(URL) / sizeof(URL[0]))]

• Uses boot count to rotate URLs
• Every wake cycle → next URL

👉 Simple but effective state machine

Smart URL encoding

EddystoneURL.setSmartURL(...)

• Automatically compresses URLs
• Uses predefined prefixes:
• Uses suffix compression where possible

👉 This reduces BLE payload size

URL limitations

• Max length ≈ 17 bytes after encoding
• Invalid cases:

// setSmartURL() returns 0 = error

👉 Always validate URLs before use

Advertising structure

oAdvertisementData.addData(data);
oScanResponseData.setName("ESP32 URLBeacon");

• Advertisement → contains encoded URL
• Scan response → contains device name

👉 Standard BLE split:

• data → primary packet
• name → scan response

BLE setup

BLEDevice::init("URLBeacon");
BLEDevice::setPower(BEACON_POWER);

• Initializes BLE stack
• Sets transmit power

#define BEACON_POWER ESP_PWR_LVL_N12

👉 Low power mode for energy efficiency

No BLE server required

// BLEServer *pServer = BLEDevice::createServer(); // not needed

• This is important
• Beacon mode does NOT require a server

👉 Saves:

• RAM
• flash
• power

Advertising cycle

pAdvertising->start();
delay(10000);
pAdvertising->stop();

• Advertises for 10 seconds
• Then stops

👉 Short bursts → better battery life

Deep sleep operation

esp_deep_sleep(1000000LL * GPIO_DEEP_SLEEP_DURATION);

• ESP32 shuts down almost completely
• Only RTC memory remains

#define GPIO_DEEP_SLEEP_DURATION 10

👉 Sleeps for 10 seconds between broadcasts

RTC memory usage

RTC_DATA_ATTR static time_t last;
RTC_DATA_ATTR static uint32_t bootcount;

• Values persist across deep sleep
• Used for:

👉 Essential for low-power state tracking

Boot diagnostics

Serial.printf("Start ESP32 %lu\n", bootcount++);

• Shows how many wake cycles occurred

Serial.printf("Deep sleep (%llds since last reset...)\n");

• Helps debug timing behavior

Runtime flow

• ESP32 wakes up
• Selects next URL
• Encodes URL
• Starts BLE advertising
• Broadcasts for 10 seconds
• Stops advertising
• Goes to deep sleep
• Repeats

👉 Fully autonomous beacon

How to scan the beacon

Use:

• ESP32 BLE scanner example
• nRF Connect (Android/iOS)
• any BLE scanner with Eddystone support

Look for:

• Service UUID: 0xFEAA
• Frame type: URL

Real-world applications

• proximity-based web links
• asset tracking tags
• smart posters / exhibits
• retail promotions
• IoT device discovery

👉 “tapless” interaction via BLE scanning

Limitations

• no connection support
• no data feedback
• limited payload size
• depends on scanner support

👉 Pure broadcast model

Improvements for production

• use dynamic URLs (e.g. sensor data endpoints)
• adjust sleep duration for battery optimization
• increase TX power for longer range
• add real sensor integration
• implement configuration via OTA or BLE setup mode

Honest take

This example is:

• simple but powerful
• extremely efficient
• underused in real projects

Big takeaway:

👉 BLE can replace QR codes in many cases

But:

• requires user to have BLE scanner
• not as universally accessible as NFC/QR

Conclusion

This example shows how to build a:

👉 low-power BLE URL broadcaster

Using:

• Eddystone URL format
• compressed advertising payload
• deep sleep cycles

It’s ideal for:

• battery-powered IoT
• proximity-based interactions
• lightweight wireless communication