In this tutorial, we will set up a configuration that allows two MKR WAN 1310's to send and receive sensor data. We will use the LoRa library to send data, and we will not use any external service. The sensor data will be recorded through the MKR ENV Shield, a shield that can record temperature, humidity, barometric pressure & ambient light.
This tutorial uses the MKR ENV shield which makes it easy to retrieve data from environmental sensors. If you have a temperature sensor or any other sensor you would like to use instead, you can make some easy adjustments to the code.
First, if we are using the MKR ENV shield, simply attach it to one of the MKR WAN 1310 boards.
Follow the wiring diagram below to connect the antennas to the MKR WAN 1310 boards.
This is the schematic of our circuit.
In this tutorial, we will use the MKR WAN 1310 board and the LoRa library to create a simple one way communication. It will teach you how to set up one board to be a sender and one board to be a receiver, and how to set up communication between these two without using any external services. We will learn how to send packages using the LoRa library, and how to receive packages.
All data received is printed in the Serial Monitor using a very simple interface.
To create the sender sketch, we will have to go through the following steps:
To create the receiver sketch, we will have to go through the following steps:
We are going to program two separate MKR WAN 1310's in this tutorial. We will start with the sender device and later on, we will create a sketch for the receiver device.
The initialization is quick and easy: we will include the SPI, LoRa and Arduino_MKRENV libraries, and create a counter variable.
1#include <Arduino_MKRENV.h>2#include <SPI.h>3#include <LoRa.h>4
5int counter = 0;
In the
setup()
we will begin serial communication, where we will use the command while(!Serial);
to prevent the program from running until we open the Serial Monitor.We will then initialize the LoRa library, where we will set the radio frequency to 868E6, which is used in Europe for LoRa® communication. If we are located in North America, we need to change this to 915E6.
As we are using the MKR ENV shield, we also need to initialize the Arduino_MKRENV library by using the line
if (!ENV.begin())
followed by an error message in case it failed to initialize.Note: If you are using another sensor, there is no need to include the Arduino_MKRENV library, or initialize it.
1void setup() {2 Serial.begin(9600);3 while (!Serial);4 Serial.println("LoRa Sender");5 6 if (!LoRa.begin(868E6)) {7 Serial.println("Starting LoRa failed!");8 while (1);9 }10 11delay(1000);12
13 if (!ENV.begin()) {14 Serial.println("Failed to initialize MKR ENV shield!");15 while (1);16 }17}
In the
loop()
we start by printing "Sending packet" in the Serial Monitor and the value of counter
. This is followed by a reading of the temperature sensor, using the command double temperature = ENV.readTemperature();
. We use a double variable, as the temperature value we record has a decimal point (e.g. 25.85).We then begin a packet by using the command,
LoRa.beginPacket()
, and print the temperature, followed by the message "celsius". This is done using the LoRa.print()
function, which we then broadcast, using the LoRa.endPacket()
command. Finally, we add increase counter by 1 each time the loop has run, and a delay of 5 seconds, to limit the message rate. This will print in the Serial Monitor, to keep track on how many transmissions we have made.
1void loop() {2 Serial.print("Sending packet: ");3 Serial.println(counter);4
5 double temperature = ENV.readTemperature();6 7 // send packet8 LoRa.beginPacket();9 LoRa.print(temperature);10 LoRa.print(" celsius");11 LoRa.endPacket();12 counter++;13 delay(5000);14}
The initialization and setup of the receiver is more or less identical to the sender sketch, but as we are writing this sketch to only receive data, we can remove the Arduino_MKRENV library.
Inside the loop, we will not be creating any packets. Instead, we will listen to incoming ones. This is done by first using the command
int packetSize = LoRa.parsePacket();
, and then check for an incoming packet. If we receive one, it is parsed, and printed in the Serial Monitor. 1#include <SPI.h>2#include <LoRa.h>3
4void setup() {5 Serial.begin(9600);6 while (!Serial);7
8 Serial.println("LoRa Receiver");9
10 if (!LoRa.begin(868E6)) {11 Serial.println("Starting LoRa failed!");12 while (1);13 }14}15
16void loop() {17 // try to parse packet18 int packetSize = LoRa.parsePacket();19 if (packetSize) {20 // received a packet21 Serial.print("Received packet '");22
23 // read packet24 while (LoRa.available()) {25 Serial.print((char)LoRa.read());26 }27
28 // print RSSI of packet29 Serial.print("' with RSSI ");30 Serial.println(LoRa.packetRssi());31 }32}
If you choose to skip the code building section, the complete code can be found below:
Once we are finished with the coding, we can upload the sketches to each board. The easiest way to go forward is to have two separate computers, as we will need to have the Serial Monitor open for both boards. Alternatively, we can use a Serial interfacing program called Putty. But for demonstration, it is good to use two computers. This way, you can move the boards further away from each other while testing the signal.
After we have uploaded the code to the sender, we need to open the Serial Monitor to initialize the program. If everything is working, it will start printing the message "Sending packet: x", where x represents the number of times the packet has been sent.
After we have uploaded the code to the receiver, we need to open the Serial Monitor to initialize the program. If everything works, we should now pick up the package we sent from the other device. The package contains the temperature, followed by RSSI (Received Signal Strength Indication). The closer this value is to 0, the stronger the signal are.
Now that we have communication between the boards, we can do a simple test with the signal. If we move the sender device away from the receiver device, we will start noticing changes in the RSSI. For example, while conducting this test, the sender device was moved around 20 meters away from the receiver, which decreased the RSSI to about -60.
As of now, we have a quite immobile setup, but this can be fixed by making the sender device mobile. A good way of testing this out is to make the sender device run on a battery instead. The MKR WAN 1310 has a battery connector that any battery with a JST PH connector can connect to. A standard 3.7 LiPo battery can power the MKR WAN 1310 for a longer time.
If the code is not working, there are some common issues we might need to troubleshoot:
This tutorial demonstrates a simple, yet powerful communication setup with the MKR WAN 1310 board and a MKR ENV Shield over the LoRa® network.