Build a LoRaWAN Node with STM32L072 and RFM95W for IoT Sensors

Building a LoRaWAN Node with STM32L072 and RFM95W for Battery-Powered IoT Sensors

This tutorial will guide you through the process of building a LoRaWAN node using the STM32L072 microcontroller and the RFM95W LoRa module. The final product will be a battery-powered IoT sensor that communicates over long distances. Follow the steps carefully to create your own LoRaWAN node.

Prerequisites

• Basic knowledge of electronics and programming
• Familiarity with the Arduino IDE or STM32CubeIDE
• A computer with USB ports
• Access to a LoRaWAN network

Parts/Tools

• STM32L072 Microcontroller
• RFM95W LoRa Module
• Battery (3.7V LiPo recommended)
• Breadboard and jumper wires
• USB to UART converter
• Arduino IDE or STM32CubeIDE
• Libraries: LoRa, SPI for Arduino or STM32

Steps

1. Set Up Your Development Environment
   • Download and install the Arduino IDE or STM32CubeIDE.
   • Install the necessary libraries:

     Arduino IDE: Sketch > Include Library > Manage Libraries
     STM32: Use Library Manager in STM32CubeIDE

2. Wiring the Components
   • Connect the STM32L072 to the RFM95W module:
     • STM32L072 DIO0 to RFM95W DIO0
     • STM32L072 SCK to RFM95W SCK
     • STM32L072 MISO to RFM95W MISO
     • STM32L072 MOSI to RFM95W MOSI
     • STM32L072 GND to RFM95W GND
     • STM32L072 3.3V to RFM95W VCC
   • Attach the battery to the power input of the STM32.
3. Configuring the Code
   • Open the Arduino IDE or STM32CubeIDE.
   • Create a new sketch or project, and include the LoRa library:

     #include <SPI.h>
     #include <LoRa.h>

   • Initialize the LoRa module in the setup function:

     void setup() {
         Serial.begin(9600);
         LoRa.begin(915E6); // Set frequency to 915MHz
     }

4. Sending Data
   • In the loop function, send a message:

     void loop() {
         LoRa.beginPacket();
         LoRa.print("Hello World");
         LoRa.endPacket();
         delay(5000); // Send every 5 seconds
     }

5. Uploading the Code
   • Connect your STM32 to the computer via USB to UART converter.
   • Select the correct board and port in the IDE.
   • Upload the code and monitor the Serial output for confirmation.
6. Testing the Node
   • Use a LoRaWAN gateway to receive messages.
   • Check the network for received data from your node.

Troubleshooting

• No Communication: Ensure all connections are secure and correct. Check power supply voltage.
• Data Not Received: Verify that the frequency matches the LoRaWAN gateway settings (e.g., 868MHz or 915MHz).
• Low Range: Check the antenna connection on the RFM95W; ensure it is properly attached.

Conclusion

Building a LoRaWAN node with the STM32L072 and RFM95W is a straightforward process that can result in a powerful battery-powered IoT sensor. By following this guide, you should now have a functioning node capable of sending data over long distances. Experiment with different sensors and data to make the most of your new IoT project.