ESP32 LoRa With Arduino IDE: Send and Receive TX RX

About: Do you like technology? Follow my channel on Youtube and my Blog. In them I put videos every week of microcontrollers, arduinos, networks, among other subjects. New tutorials on Tuesdays and Fridays.

Following suggestions from my YouTube channel’s followers, we will talk about the ESP32 LoRa again today. However, this time we’ll discuss sending and receiving data by the same device. In this situation, an ESP32 LoRa, the Master, will send a packet warning that it wants to receive the data, while another device, the Slave, will wait for the command to send the data back to the Master. This is unlike other videos I've done that featured an ESP32 LoRa as Sender and another as Receiver, as today we will have the same device, the Master, that will send and receive data.

Step 1: LoRa ESP32 Pinout

Here is the PinOut of ESP32 LoRa. It is important to remember that whenever we use this model, it is already using its SPI ports. The pins that are already being used by the LoRa chip are in the image where I put the red arrows, which is below the display.

Step 2: Communication

I show here the working scheme of our project, in which the Master sends a data packet to the Slave, which sends this information back to the Master, a cycle that continues to be repeated in an infinite loop.

Step 3: Demonstration

You can see in the video the two chips exchanging information.

Step 4: Source Code

LoRaSendReceive.ino

At first, we'll include the libraries and set the GPIO destinations, as well as the radio frequency. Also, let's create constants to tell the Slave about the data jobs. In this step, we also have a variable to control the display.

#include <SPI.h>
#include <LoRa.h> #include <Wire.h> #include <SSD1306.h> //Deixe esta linha descomentada para compilar o Master //Comente ou remova para compilar o Slave // #define MASTER #define SCK 5 // GPIO5 SCK #define MISO 19 // GPIO19 MISO #define MOSI 27 // GPIO27 MOSI #define SS 18 // GPIO18 CS #define RST 14 // GPIO14 RESET #define DI00 26 // GPIO26 IRQ(Interrupt Request) #define BAND 433E6 //Frequência do radio - exemplo : 433E6, 868E6, 915E6 //Constante para informar ao Slave que queremos os dados const String GETDATA = "getdata"; //Constante que o Slave retorna junto com os dados para o Master const String SETDATA = "setdata="; //Variável para controlar o display SSD1306 display(0x3c, 4, 15);

LoRaSendReceive.ino - setupDisplay

In this first setup, we will deal with the configuration of the display.

void setupDisplay(){
//O estado do GPIO16 é utilizado para controlar o display OLED pinMode(16, OUTPUT); //Reseta as configurações do display OLED digitalWrite(16, LOW); //Para o OLED permanecer ligado, o GPIO16 deve permanecer HIGH //Deve estar em HIGH antes de chamar o display.init() e fazer as demais configurações, //não inverta a ordem digitalWrite(16, HIGH); //Configurações do display display.init(); display.flipScreenVertically(); display.setFont(ArialMT_Plain_10); display.setTextAlignment(TEXT_ALIGN_LEFT); }

LoRaSendReceive.ino - setupLoRa

Here, we’ll look at the initial LoRa settings.

//Configurações iniciais do LoRa
void setupLoRa(){ //Inicializa a comunicação SPI.begin(SCK, MISO, MOSI, SS); LoRa.setPins(SS, RST, DI00); //Inicializa o LoRa if (!LoRa.begin(BAND, true)){ //Se não conseguiu inicializar, mostra uma mensagem no display display.clear(); display.drawString(0, 0, "Erro ao inicializar o LoRa!"); display.display(); while (1); } //Ativa o crc LoRa.enableCrc(); //Ativa o recebimento de pacotes LoRa.receive(); }

Step 5: Master.ino

In this part, we work with the configurations that involve the Master, configurations on the compilation, the interval between shipments, and the time of the last shipment.

//Compila apenas se MASTER estiver definido no arquivo principal
#ifdef MASTER //Intervalo entre os envios #define INTERVAL 500 //Tempo do último envio long lastSendTime = 0;

Master.ino - setup

Here, we call up the initial display and LoRa settings.

void setup(){
Serial.begin(115200); //Chama a configuração inicial do display setupDisplay(); //Chama a configuração inicial do LoRa setupLoRa(); display.clear(); display.drawString(0, 0, "Master"); display.display(); }

Master.ino - loop

In this Loop, we define the sending of the package to inform the Slave about our preference to receive data, and also check if there are packages to be received.

void loop(){
//Se passou o tempo definido em INTERVAL desde o último envio if (millis() - lastSendTime > INTERVAL){ //Marcamos o tempo que ocorreu o último envio lastSendTime = millis(); //Envia o pacote para informar ao Slave que queremos receber os dados send(); } //Verificamos se há pacotes para recebermos receive(); }

Master.ino - receive 1/2

We run an attempt to read the package, check if it has a minimum expected character size, and store the data in a string, which must have what is contained in "SETDATA.”

void receive(){
//Tentamos ler o pacote int packetSize = LoRa.parsePacket(); //Verificamos se o pacote tem o tamanho mínimo de caracteres que esperamos if (packetSize > SETDATA.length()){ String received = ""; //Armazena os dados do pacote em uma string while(LoRa.available()){ received += (char) LoRa.read(); } //Verifica se a string possui o que está contido em "SETDATA" int index = received.indexOf(SETDATA);

Master.ino - receive 2/2

Now, we retrieve the String that is after the "SETDATA,” which, in this case, is the data we’re interested in. We also analyzed the time it took for the Master to create and send the package, and how long it took for the Slave to receive, read, create a new package, send it, and also for the time it took to be received again by the Master. We then display the data, and the time the operation required.

if(index >= 0){
//Recuperamos a string que está após o "SETDATA", //que no caso serão os dados de nosso interesse String data = received.substring(SETDATA.length()); //Tempo que demorou para o Master criar o pacote, enviar o pacote, //o Slave receber, fazer a leitura, criar um novo pacote, enviá-lo //e o Master receber e ler String waiting = String(millis() - lastSendTime); //Mostra no display os dados e o tempo que a operação demorou display.clear(); display.drawString(0, 0, "Recebeu: " + data); display.drawString(0, 10, "Tempo: " + waiting + "ms"); display.display(); } } } #endif

Step 6: Slave.ino

Starting the Slave code, we compile only if the Master is not defined in the main file. Here, we have the Counter that will act as the data that the Slave will send.

//Compila apenas se MASTER não estiver definido no arquivo principal
#ifndef MASTER //Contador que irá servir como o dados que o Slave irá enviar int count = 0;

Slave.ino - Setup

In Slave Setup, we call up the initial display and LoRa settings.

void setup(){
Serial.begin(115200); //Chama a configuração inicial do display setupDisplay(); //Chama a configuração inicial do LoRa setupLoRa(); display.clear(); display.drawString(0, 0, "Slave esperando..."); display.display(); }

Slave.ino - Loop 1/2

Just like in the Master, in this part of the Slave Loop, we execute an attempt to read the package, check if it has the expected number of characters, and store the data in a String.

void loop(){
//Tenta ler o pacote int packetSize = LoRa.parsePacket(); //Verifica se o pacote possui a quantidade de caracteres que esperamos if (packetSize == GETDATA.length()){ String received = ""; //Armazena os dados do pacote em uma string while(LoRa.available()){ received += (char) LoRa.read(); }

Slave.ino - Loop 2/2

Now, we simulate the reading of the data. We create the package, finalize it, and send it. Finally, we display the information on the display.

if(received.equals(GETDATA)){
//Simula a leitura dos dados String data = readData(); Serial.println("Criando pacote para envio"); //Cria o pacote para envio LoRa.beginPacket(); LoRa.print(SETDATA + data); //Finaliza e envia o pacote LoRa.endPacket(); //Mostra no display display.clear(); display.drawString(0, 0, "Enviou: " + String(data)); display.display(); } } }

Lastly, here is a function to read the data you want to send. It could be the value read by some sensor, for example. Here, in our project, we will send only one counter for tests, but you can change the function to read the data of your preference.

//Função onde se faz a leitura dos dados que queira enviar
//Poderia ser o valor lido por algum sensor por exemplo //Aqui vamos enviar apenas um contador para testes //mas você pode alterar a função para fazer a leitura de algum sensor String readData(){ return String(count++); } #endif

Share

    Recommendations

    • Optics Contest

      Optics Contest
    • Make it Glow Contest 2018

      Make it Glow Contest 2018
    • Plastics Contest

      Plastics Contest

    Discussions

    0
    None
    mae8

    Question 2 months ago on Step 6

    Hello Fernando,

    I did the project and it works like a charm, many thanks for this simple example.

    I've tried to send another set of data, but the slave never receive it, at least it's not written in serial monitor.

    // EDIT : I've found my error

    the receive function has to be updated to handle the date received, and not only the "getdata" frames.

    Thanks again, and sorry for disturbing on a so simple case :-)

    Here is the piece of code I've added :

    in main code :

    const String oléolé = "oyee_o";

    in "master" main loop :

    after send("getdata"); :

    delay(10);

    send("olé_olé")

    Did you try to send more data?

    thanks for you help.

    mael