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LoRa is a wireless technology that enables long-range, low-power, and low-cost communication. LoRa devices can transmit data over distances of up to 15 km in rural areas and 5 km in urban areas, using very little battery power. This technology is well suited for the low transmission rate application.
In this campaign, we use the LoRa technology to create an open-source form-factor Call Bell application. There are two devices in one set, one serves as a transmitter (call bell) and the other serves as a receiver (adapter). Both the transmitter and receiver are using the same hardware, they can be swapped by flashing different firmware.
What’s inside in the hardware?The hardware is running by Espressif ESP32-S3, a dual-core XTensa LX7 MCU, capable of running at 240 MHz. The MCU comes with 512KB internal SRAM, and integrated 2.4GHz, 802.11 b/g/n Wi-Fi and Bluetooth 5 (LE) connectivity.
LoRa communication is done by Semtech’s LLCC68, a sub-GHz RF transceiver that supports LoRa modulation for LPWAN use cases and (G)FSK modulation for legacy use cases.
User interface
One user button is for human-to-machine interaction. The pre-installed firmware supports the following events:
There are two RGB LEDs on the hardware: LED1, which indicates data communication status, and LED2, which indicates battery charging status.
When the “Transmitter” device is transmitting or receiving data, the green LED of LED1 flashes.
When the “Receiver” device is transmitting or receiving data, the blue LED of LED1 flashes.
When the device is in a low battery state, the red LED of LED2 blinks.
When the “Transmitter” device is charging, the green LED of LED2 blinks.
When the “Transmitter” device is fully charged, the green LED of LED2 turns on.
When the “Receiver” device is charging, the blue LED of LED2 blinks.
When the “Transmitter” device is fully charged, the blue LED of LED2 turns on.
Arduino is an open-source platform for creating and controlling interactive electronic objects. It consists of a hardware board, a software IDE, and a community of users and developers. Arduino supports various programming languages, libraries, and sensors. Arduino is ideal for beginners, hobbyists, and professionals who want to explore electronics and coding.
Arduino-ESP32 supports FreeRTOS, an open-source real-time operating system (RTOS) for microcontrollers and small microprocessors. It provides a kernel and libraries for connectivity, security, and over-the-air updates.
This project leverages Arduino, ESP32-S3 and FreeRTOS to make it easier for developers to implement a commercial Lora Call Bell application in a short time. For those who worry about the robustness of Arduino, we have experience in developing a commercial SubG gateway with Arduino, Pi Pico and Mbed OS, which has been running for more than 2 years without rebooting.
There are a couple of Arduino libraries required for building this project. They are:
* Arduino-ESP32 (https://docs.espressif.com/projects/arduino-esp32/en/latest/installing.html)
* Arduino-ESP32 (https://docs.espressif.com/projects/arduino-esp32/en/latest/installing.html)
* Arduino RadioLib (https://www.arduino.cc/reference/en/libraries/radiolib/)
* Arduino DebugLog (https://www.arduino.cc/reference/en/libraries/debuglog/)
* ArduinoJson (https://github.com/bblanchon/ArduinoJson)
* RingBuffer (https://www.arduino.cc/reference/en/libraries/ringbuffer/)
* ArduProf lib (https://www.arduino.cc/reference/en/libraries/arduprof/)
The Arduino-ESP32 library is essential to run Arduino on the ESP32-S3 MCU.
The Arduino RadioLib library provides APIs to interact with the LLCC68 LoRa chip.
The Arduino DebugLog library provides APIs to log debug message.
The ArduinoJson library simplifies json encoding and decoding operations.
The ArduProf lib library provides a thin layer framework that makes it easier for developers to code inter-task communication by an event driven method.
After installing the required libraries, complete the following task one by one.
Build and flash the firmware
1. download and extract the source of this project from https://github.com/teamprof/github-lora-call-bell
2. launch the Arduino IDE
3. open the sketch github-lora-call-bell.ino,
4. select ESP32-S3 by clicking “Menu” -> “Tools” -> “Select Board” -> “ESP32S3 Dev Module”
5. build the code by clicking “Menu” -> “Sketch” -> “Compile/Verify”
6. select the port by clicking “Menu” -> “Tools” -> “Port”
7. build the code by clicking “Menu” -> “Sketch” -> “Upload”
If everything goes smoothly, you should see the following screen.
Test the LoRa Call Bell set
There are two pieces of hardware in one set. They are pre-installed with “Transmitter” firmware and “Receiver” firmware.
1. power up the “Transmitter” by connecting it to a power bank with a micro USB cable. The green LED of LED2 blinks.
2. connect the “Receiver” to PC with a micro USB cable. The blue LED of LED2 blinks.
3. launch a Serial Terminal on PC, connect it to the “Receiver” USB/virtual port with 115200bps, 8N1
4. press the button on the “Transmitter”, the green LED of LED1 on the “Transmitter” flashes.
5. on “Receiver”, the blue LED of LED1 flashes during receiving data. A json-format message should be shown on the Serial Terminal.
Note: json format of received package:
{ "event": "call-data", "sid": src_id, "seq": seq_num, "rssi": rssi, "snr": snt, "data": data }
e.g. call button with device ID=1001 sends bytes 0x02, 0x01 with sequence number=0
{ "event": "call-data", "sid": 1001, "seq": 0, "rssi":, "snr":, "data": [2, 1] }
Switch between “Transmitter” firmware and “Receiver” firmware
Switching between “Transmitter” and “Receiver” is done by changing the “device type” in the “deviceConfig” in the “lora-call-bell.ino”.
Setting Device ID parameter
The “Device ID” parameter is configured in the “device id” in “deviceConfig” section in the “lora-call-bell.ino”.
Setting LoRa RF parameters
The LoRa RF parameters are configured in the “rfConfig” in “deviceConfig” section in the “lora-call-bell.ino”.
The campaign is running on Kickstarter: https://www.kickstarter.com/projects/teamprof/lora-call-bell-development-board
Source code will be available on GitHub once the campaign goes into the mass production stage.
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