Getting started with RFM95W, LoRa and ESP32

In this blog post I will be introducing you to LoRa using the RFM95W module with an ESP32, so let’s get started. I also wrote a tutorial for the ESP8266.

First, we should talk about what LoRa is and what it stands for. LoRa stands for Long Range and as the name suggests one of its main aspects is its considerable range. However, we need to make a distinction between LoRa and LoRaWAN. In this tutorial, I will be talking about LoRa. LoRaWAN adds another layer of authentification. Services like TheThingsNetwork (TTN) use LoRaWAN. However, LoRa is easier to use and understand for this tutorial.

Hardware used / Preparation

For this tutorial, I will be using an RFM95W module with an ESP32. The RFM95W is our LoRa communication chip. I’ve got my ESP from the german seller AZ-Delivery (I’m not affiliated with them in any way nor do I get any money from them for mentioning their name). My RFM95W comes from Amazon.

For this, I will assume that your Arduino IDE is set up to work with ESP32s. If not here is a tutorial to do it.

Wiring

If you have a different ESP you can check the documentation supplied below for further details.

Now get started, for real

As a first step build up the setup shown above. Next, you need to install the LoRa Libary by Sandeep Mistry. More documentation is available here.

This code is actually the library’s example code modified to give a little more output.

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

int counter = 0;
// - Pin configs -
#define ss 5
#define rst 14
#define dio0 2

void setup() {
  Serial.begin(115200);
  while (!Serial);
  delay(1000);

  Serial.println("LoRa Sender");
  // Setup LoRa transceiver module
  LoRa.setPins(ss, rst, dio0);
  
  if (!LoRa.begin(868E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }else{
    Serial.println("Starting LoRa successful");
    }
  
}

// Sends a string every 5000ms (5 seconds)
void loop() {
  Serial.print("Sending packet: ");
  Serial.println(counter);

  // send packet
  LoRa.beginPacket();
  LoRa.print("hello ");
  LoRa.print(counter);
  LoRa.endPacket();

  counter++;

  delay(5000);
}

I’ve had some issues using the code out-of-the-box. Some problems are due to the code lacking a lot of verbosity and some are due to user problems. The code above fixes one of the issues, verbosity. The other one is addressed below.

After changing your frequencies and making sure that you use the right board, hit the upload button. After the upload is done open your serial console, select 115200 baud. Then you should see this output:

And finally, your ESP is sending LoRa. Some of the items I need for receiving are stuck in shipping this has to wait for another day. However, below is a short paragraph for those who already own an SDR.

Does this even work? For people with SDRs

This paragraph is made for people who own SDRs (SoftwareDefinedRadio). For this, I’m using a VM running ParrotOS. This image comes preinstalled with SDR++. GNUradio and a bunch of extensions for GNUradio. These extensions also contain gr-lora, which I will be using here. Following this tutorial in the wiki, you should be able to set up your workspace to receive LoRa messages. Please also remember to use the right frequency. The results looks something like this:

With this setup, I was able to use a pretty good range, even though I only used a so-called random wire antenna. This also shows how some packets are missing some data. This shows why you should always use the hash numbers to verify that the received packet is healthy. I will be talking about hashes sometime in the future.

I hope I could get you on your way into the interesting world of LoRa.