BLE iBeacon scanner and advertizer

This program runs on an Espressif EPS32 microcontroller and advertizes or scan for iBeacons.

One of my sons used this as a tool to research the behavior of Bluetooth Low-Energy (BLE) signals in relation to contact tracing for MIT PACT.

Features:

• Supports both BLE advertiser and scan modes
• Advertize interval is configurable
• Controlled and data presented through MQTT
• Supports over-the-air updates ¹
• Easily one-time provisioning from an Android phone ¹

The full fledged project installation method is described in the FULL_INSTALL.md. Before you go down that road, you may want to give it a quick spin to see what it can do. The remainder of this README will walk you through this.

The devices interface using the MQTT protocol.

MQTT stands for MQ Telemetry Transport. It is a publish/subscribe, extremely simple and lightweight messaging protocol, designed for constrained devices and low-bandwidth, high-latency or unreliable networks. FAQ

Hardware

No soldering required.

⚠️ THIS PROJECT IS OFFERED AS IS. IF YOU USE IT YOU ASSUME ALL RISKS. NO WARRENTIES.

Bill of materials

Name	Description	Sugggested mfr/part#
ESP32BRD	ESP32 development board	ESP32-DevKitC-VB
BROKER	Device to run MQTT Broker such as Mosquitto	Raspberry Pi 4

Software

Clone the repository and its submodules to a local directory. The --recursive flag automatically initializes and updates the submodules in the repository,.

git clone --recursive https://github.com/cvonk/BLEscan
cd BLEscan
cp scanner/Kconfig.example scanner/Kconfig
cp factory/Kconfig.example factory/Kconfig

ESP-IDF

If you haven't installed ESP-IDF, I recommend the Microsoft Visual Studio Code IDE (vscode). From vscode, add the Microsoft's C/C++ extension. Then add the Espressif IDF extension and follow its configuration to install ESP-IDF 4.4.

ESP32 Device

In menuconfig, scroll down to BLEscan and select "Use hardcoded Wi-Fi credentials" and specify the SSID and password of your Wi-Fi access point. Then select "Use hardcoded MQTT URL" and specify the URL to the MQTT broker in the form mqtt://mqtt:passwd@host.domain:1883.

cd scanner
idf.py set-target esp32
idf.py menuconfig
idf.py flash

Using the devices

Both replies to control messages and scan results are reported using MQTT topic blescan/data/SUBTOPIC/DEVNAME.

Subtopics are:

• scan, BLE scan results,
• mode, response to mode and int control messages,
• who, response to who control messages,
• restart, response to restart control messages,
• dbg, general debug messages

The easiest way for running the Mosquitto MQTT client under Microsoft Windows is by using Windows Subsystem for Linux.

sudo apt-get update.
sudo apt-get install mosquitto.
sudo apt-get install mosquitto-clients.

E.g. to listen to all scan results, use:

mosquitto_sub -t "blescan/data/scan/#" -v

where # is a the MQTT wildcard character.

Modes

The device support three modes:

• adv, the device advertises iBeacon messages
• scan, the device scans for iBeacon messages and reports them using MQTT
• idle, the device neither advertises or scans

To switch modes, sent a control message with the new mode to:

• blescan/ctrl, a group topic that all devices listen to, or
• blescan/ctrl/DEVNAME, only DEVNAME listens to this topic.

Here DEVNAME is either a programmed device name, such as esp32-1, or esp32_XXXX where the XXXX are the last digits of the MAC address. Device names are assigned based on the BLE MAC address in main/ble_task.c.

mosquitto_pub -t "blescan/ctrl" -m SEE_BELOW	mosquitto_sub -t "blescan/data/#"
mode	{ "response": { "mode": "ADV", "interval": 40 } }
scan	{ "response": { "mode": "SCAN", "interval": 40 } }
int 100	{ "response": { "mode": "SCAN", "interval": 100 } }
adv	{ "response": { "mode": "ADV", "interval": 100 } }
idle	{ "response": { "mode": "IDLE", "interval": 100 } }

Other controls

Other control messages are:

• who, can be used for device discovery when sent to the group topic
• restart, to restart the ESP32 (and check for OTA updates)
• int N, to change scan/adv interval to N milliseconds (40 .. 1000 msec)
• mode, to report the current scan/adv mode and interval

Multiple devices

Messages can be sent to a specific device, or the whole group:

mosquitto_pub -t "blescan/ctrl/esp-1" -m "who"
mosquitto_pub -t "blescan/ctrl" -m "who"

In one terminal listen for the reponses from all devices

mosquitto_sub -t "blescan/data/#" -v

In another terminal sent the command to all devices

mosquitto_pub -t "blescan/ctrl" -m who

The first terminal will show the scan results

blescan/data/who/esp32-1 { "ble": {"name": "esp32-1", "address": "30:ae:a4:cc:24:6a"}, "firmware": { "version": "scanner.v1.0", "date": "Apr 28 2022 16:20:28" }, "wifi": { "connect": 1, "address": "10.1.1.120", "SSID": "Guest Barn", "RSSI": -51 }, "mqtt": { "connect": 1 }, "mem": { "heap": 115692 } }
blescan/data/who/esp32-4 { "ble": {"name": "esp32-4", "address": "ac:67:b2:53:7f:22"}, "firmware": { "version": "scanner.v1.0", "date": "Apr 28 2022 16:20:28" }, "wifi": { "connect": 1, "address": "10.1.1.123", "SSID": "Guest Barn", "RSSI": -66 }, "mqtt": { "connect": 1 }, "mem": { "heap": 115636 } }
blescan/data/who/esp32-3 { "ble": {"name": "esp32-3", "address": "ac:67:b2:53:82:8a"}, "firmware": { "version": "scanner.v1.0", "date": "Apr 28 2022 16:20:28" }, "wifi": { "connect": 1, "address": "10.1.1.122", "SSID": "Guest Barn", "RSSI": -58 }, "mqtt": { "connect": 1 }, "mem": { "heap": 115636 } }
blescan/data/who/esp32-2 { "ble": {"name": "esp32-2", "address": "30:ae:a4:cc:32:4e"}, "firmware": { "version": "scanner.v1.0", "date": "Apr 28 2022 16:20:28" }, "wifi": { "connect": 1, "address": "10.1.1.121", "SSID": "Guest Barn", "RSSI": -65 }, "mqtt": { "connect": 1 }, "mem": { "heap": 115716 } }

Scan example

In one terminal listen for the reponses

mosquitto_sub -t "blescan/data/#" -v

In another terminal sent the commands. First put all devices in advertizing mode, then put one device in scanning mode.

mosquitto_pub -t "blescan/ctrl" -m adv
mosquitto_pub -t "blescan/ctrl/esp32-2" -m scan

The first terminal will show the scan results

blescan/data/mode/esp32-3 { "response": { "mode": "ADV", "interval": 40 } }
blescan/data/mode/esp32-2 { "response": { "mode": "ADV", "interval": 40 } }
blescan/data/mode/esp32-4 { "response": { "mode": "ADV", "interval": 40 } }
blescan/data/mode/esp32-1 { "response": { "mode": "ADV", "interval": 40 } }
blescan/data/mode/esp32-1 { "response": { "mode": "SCAN", "interval": 40 } }
blescan/data/scan/esp32-1 { "name": "esp32-3", "address": "ac:67:b2:53:82:8a", "txPwr": -59, "RSSI": -40 }
blescan/data/scan/esp32-1 { "name": "esp32-4", "address": "ac:67:b2:53:7f:22", "txPwr": -59, "RSSI": -38 }
blescan/data/scan/esp32-1 { "name": "esp32-2", "address": "30:ae:a4:cc:32:4e", "txPwr": -59, "RSSI": -37 }
blescan/data/scan/esp32-1 { "name": "esp32-2", "address": "30:ae:a4:cc:32:4e", "txPwr": -59, "RSSI": -39 }
blescan/data/scan/esp32-1 { "name": "esp32-3", "address": "ac:67:b2:53:82:8a", "txPwr": -59, "RSSI": -39 }
blescan/data/scan/esp32-1 { "name": "esp32-3", "address": "ac:67:b2:53:82:8a", "txPwr": -59, "RSSI": -38 }
blescan/data/scan/esp32-1 { "name": "esp32-4", "address": "ac:67:b2:53:7f:22", "txPwr": -59, "RSSI": -37 }
blescan/data/scan/esp32-1 { "name": "esp32-3", "address": "ac:67:b2:53:82:8a", "txPwr": -59, "RSSI": -36 }
blescan/data/scan/esp32-1 { "name": "esp32-4", "address": "ac:67:b2:53:7f:22", "txPwr": -59, "RSSI": -37 }
blescan/data/scan/esp32-1 { "name": "esp32-2", "address": "30:ae:a4:cc:32:4e", "txPwr": -59, "RSSI": -40 }
blescan/data/scan/esp32-1 { "name": "esp32-2", "address": "30:ae:a4:cc:32:4e", "txPwr": -59, "RSSI": -37 }
blescan/data/scan/esp32-1 { "name": "esp32-3", "address": "ac:67:b2:53:82:8a", "txPwr": -59, "RSSI": -36 }
blescan/data/scan/esp32-1 { "name": "esp32-4", "address": "ac:67:b2:53:7f:22", "txPwr": -59, "RSSI": -37 }
blescan/data/scan/esp32-1 { "name": "esp32-2", "address": "30:ae:a4:cc:32:4e", "txPwr": -59, "RSSI": -39 }
blescan/data/scan/esp32-1 { "name": "esp32-4", "address": "ac:67:b2:53:7f:22", "txPwr": -59, "RSSI": -38 }

Feedback

We love to hear from you. Please use the Github channels to provide feedback.

Footnotes

1. Available with the full install as described in FULL_INSTALL.md ↩ ↩²