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2020/02/03

Seeing LoRa transmission in action using a RTL-SDR dongle and SDR# software

In this post, I use a RTL-SDR dongle and SDR# software to watch the transmission of LoRa signal at 433MHz. For info. on how to set up the RTL-SDR, please refer to the post below.

https://wei48221.blogspot.com/2020/02/how-to-setup-rtl-sdr-dongle-to-work.html

Sender Code (running on ESP8266)

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/*********
  Modified from the examples of the Arduino LoRa library
  More resources: https://randomnerdtutorials.com
*********/

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

//define the pins used by the transceiver module
//#define ss 5
//#define rst 14
//#define dio0 2 // GO of the Adafruit RFM9x breakout module

#define ss 15
#define rst 0
#define dio0 16 // GO of the Adafruit RFM9x breakout module

int counter = 0;

void setup() {
  //initialize Serial Monitor
  Serial.begin(115200);
  while (!Serial);
  Serial.println("LoRa Sender");

  //setup LoRa transceiver module
  LoRa.setPins(ss, rst, dio0);
  
  //replace the LoRa.begin(---E-) argument with your location's frequency 
  //433E6 for Asia
  //866E6 for Europe
  //915E6 for North America
  /*
  while (!LoRa.begin(866E6)) {
    Serial.println(".");
    delay(500);
  }
  */
  
  while (!LoRa.begin(433E6)) {
    Serial.println(".");
    delay(500);
  }

  // Change sync word (0xF3) to match the receiver
  // The sync word assures you don't get LoRa messages from other LoRa transceivers
  // ranges from 0-0xFF
  LoRa.setSyncWord(0xF3);
  Serial.println("LoRa Initializing OK!");
}

void loop() {
  Serial.print("Sending packet: ");
  Serial.println(counter);

  //Send LoRa packet to receiver
  LoRa.beginPacket();
  LoRa.print("hello ");
  LoRa.print(counter);
  LoRa.endPacket();

  counter++;

  delay(10000);
}

Receiver Code (running on ESP32)

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/*********
  Modified from the examples of the Arduino LoRa library
  More resources: https://randomnerdtutorials.com
*********/

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

//define the pins used by the transceiver module
//#define ss 5
//#define rst 14
//#define dio0 2

#define ss 21   // GPIO21 of ESP32 
#define rst 17  // GPIO17 of ESP32
#define dio0 16 // Connect to G0 of the Adafruit RFM9x breakout module

void setup() {
  //initialize Serial Monitor
  Serial.begin(115200);
  while (!Serial);
  Serial.println("LoRa Receiver");

  //setup LoRa transceiver module
  LoRa.setPins(ss, rst, dio0);
  
  //replace the LoRa.begin(---E-) argument with your location's frequency 
  //433E6 for Asia
  //866E6 for Europe
  //915E6 for North America
  /*
  while (!LoRa.begin(866E6)) {
    Serial.println(".");
    delay(500);
  }
  */
  
  while (!LoRa.begin(433E6)) {
    Serial.println(".");
    delay(500);
  }
  
  // Change sync word (0xF3) to match the receiver
  // The sync word assures you don't get LoRa messages from other LoRa transceivers
  // ranges from 0-0xFF
  LoRa.setSyncWord(0xF3);
  Serial.println("LoRa Initializing OK!");
}

void loop() {
  // try to parse packet
  int packetSize = LoRa.parsePacket();
  if (packetSize) {
    // received a packet
    Serial.print("Received packet '");

    // read packet
    while (LoRa.available()) {
      String LoRaData = LoRa.readString();
      Serial.print(LoRaData); 
    }

    // print RSSI of packet
    Serial.print("' with RSSI ");
    Serial.println(LoRa.packetRssi());
  }
}

Serial Output


SDR# Display (Youtube Video)

The pulse at 433MHz is the signal sent by the sender.


Reference:

QUICK START GUIDE
https://www.rtl-sdr.com/rtl-sdr-quick-start-guide/

Airspy
https://airspy.com/
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