Heltec Lora esp32 Data sending on 433MHz but not on 868MHz

[abhimanyuJadli]

I am using Heltec WiFi ESP32 LoRa board and a TTGO LoRa board and the code involves Tx sending 8 packets of data with a suitable delay and then Rx combines into a json and then send it to the cloud.
RX CODE:

#include “heltec.h”
#include <ArduinoJson.h>
#include <WiFi.h>
#include <HTTPClient.h>
#define Central_ID 1
#define FIXEDTXCOUNT 9
#define BAND 433E6 //you can set band here directly,e.g. 868E6,915E6
#include “DHT.h”
#define DHTPIN 13
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

const int csPin = 18; // LoRa radio chip select
const int resetPin = 14; // LoRa radio reset
const int irqPin = 26; // change for your board; must be a hardware interrupt pin

String dataReceived;

const char* ssid = “abcdefghi”;
const char* password = “***********”;
const char* host = “https://firetracker.online/index.php”;

byte localAddress = 0; // address of this device
byte destination = 0; // destination to send to
long lastSendTime = 0; // last send time
unsigned long interval = 5000; // interval between sends
int NodeID_Flag[FIXEDTXCOUNT];

// ---------------------------------
// Flags
int flagPacketProcessed = 1;
int flagDataAvailable = 0;

void setup()
{
Serial.begin(9600); // initialize serial
pinMode(4,INPUT);
dht.begin();
//WIFI Kit series V1 not support Vext control
Heltec.begin(true /DisplayEnable Enable/, true /Heltec.LoRa Disable/, true /Serial Enable/, true /PABOOST Enable/, BAND /long BAND/);
LoRa.setPins(csPin, resetPin, irqPin);
LoRa.onReceive(onReceive);
LoRa.receive();
for (int ii = 0; ii < FIXEDTXCOUNT; ii++)
{
NodeID_Flag[ii] = 0;
}
Serial.println(ssid);
// WiFi.begin(ssid, password);

// while (WiFi.status() != WL_CONNECTED) {
// delay(500);
// Serial.print(".");
// }

Serial.println("");
Serial.println(“WiFi connected”);
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
}
StaticJsonDocument<400> DeserializeReceive;
StaticJsonDocument<1600> doc;
JsonObject Central = doc.createNestedObject(“Central node”);
JsonObject Data = Central.createNestedObject(“Data”);

void loop()
{
if ((millis() - lastSendTime > interval) || flagPacketProcessed == 1)
{
destination = destination + 1;
String message = String (destination); // send a message
if (destination <= 8)
{ sendMessage(message);
Serial.println("Sending " + message);
}
lastSendTime = millis(); // timestamp the message
// interval = 3000;
flagPacketProcessed = 0; //flag set so that no new data is sent till a packet is received
// interval = 5000;
if (destination > 9)
{
destination = 0;
}
LoRa.receive(); // go back into receive mode
}
Central[“id”] = Central_ID;
if (flagDataAvailable == 1)
{
String dataReceivedCopy = dataReceived;
Central[“id”] = Central_ID;
//////////////////////////////////////////////////////////////////
/Deserialize incoming data to check Node ID/
//////////////////////////////////////////////////////////////////
DeserializationError error1 = deserializeJson(DeserializeReceive, dataReceived);

// Test if parsing succeeds.
if (error1) {
  Serial.print(F("deserializeJson() failed: "));
  Serial.println(error1.c_str());
  return;
}

/////////////////////////////////////////////////////////
/*Extract Node ID and make object key with same name */
////////////////////////////////////////////////////////
char buf[50];
String b = "Node";
long testID = DeserializeReceive["NODE_ID"];
sprintf(buf, "%lu", testID);
String a = b + buf;
Data[a] = serialized(dataReceivedCopy);

/////////////////////////////////////////////////////////
/* raise flags for packets from received nodes */
/////////////////////////////////////////////////////////
if (testID >= 0)
{
  NodeID_Flag[testID] = 1;
}
flagPacketProcessed = 1;
flagDataAvailable = 0;

}
/***********************************************************************
counter to check send message/destination counts
***********************************************************************/
if (destination == 9)
{ ///////////////////////////////////////////////////////////////
// embedd entries for data from non receiving nodes //
///////////////////////////////////////////////////////////////
for (int ii = 1; ii < FIXEDTXCOUNT; ii++)
{
if (NodeID_Flag[ii] == 0)
{ String d = “Node” + String(ii);
Data[d] = “\0”;
}
}
///////////////////////////////////////////////////////////////
// data from central Node //
//////////////////////////////////////////////////////////////
JsonObject CentralNode = Data.createNestedObject(“Central”);
CentralNode[“Node_ID”] = 0;
CentralNode[“Temperature”] = dht.readTemperature();
CentralNode[“Humidity”] = dht.readHumidity();
CentralNode[“Smoke”] = digitalRead(4);
CentralNode[“Rain”] = 1;

////////////////////////////////////////////////////////////////////////////
// data from special sensors at central node to be duplicated for all Node /
////////////////////////////////////////////////////////////////////////////
JsonObject Combined = Data.createNestedObject("Combined");
Combined["CO2"] = 667;
Combined["PM 2.5"] = 876;
Combined["PM 10"] = 343;
Combined["NO2"] = 745;
Combined["NH3"] = 233;
Combined["CO"] = 988;
Combined["Wind Direction"] = "NW"; //
// char dir[8]={"NW","N","NE","E","SE","S","SW',"W"}
Combined["Wind Speed"] = 343;
String wifidata = "";

serializeJson(doc, wifidata);                       //Final Json to be sent
Serial.println(wifidata);
if (WiFi.status() == WL_CONNECTED) {
  HTTPClient http;
  http.begin(host);
  http.addHeader("Content-Type", "application/x-www-form-urlencoded");
  String url = "&value=";
  url += wifidata;
  Serial.print("Requesting URL: ");
  Serial.println(url);
  int httpResponseCode = http.POST(url);
  if (httpResponseCode > 0) {
    Serial.print("HTTP Response code: ");
    Serial.println(httpResponseCode);
  }
  else {
    Serial.print("Error code: ");
 Serial.println(httpResponseCode);      }
  // Free resources
  http.end();
}
else {
  Serial.println("WiFi Disconnected");
}
//Send an HTTP POST request every 3 seconds
// delay(60000);

for (int ii = 1; ii < FIXEDTXCOUNT; ii++)               // Clear all Flags for nodes
{
  NodeID_Flag[ii] = 0;
}
doc.clear();
//clear JsonDocument else data will be repeated
JsonObject Central = doc.createNestedObject("Central node");
JsonObject Data = Central.createNestedObject("Data");
flagPacketProcessed = 1;

}
}

void sendMessage(String outgoing)
{
LoRa.beginPacket(); // start packet
LoRa.write(destination); // add destination address
LoRa.write(localAddress); // add sender address
LoRa.write(outgoing.length()); // add payload length
LoRa.print(outgoing); // add payload
LoRa.endPacket(); // finish packet and send it
}

void onReceive(int packetSize)
{
if (packetSize == 0) return; // if there’s no packet, return

// read packet header bytes:
int recipient = LoRa.read(); // recipient address
byte sender = LoRa.read(); // sender address
byte incomingLength = LoRa.read(); // incoming msg length

String incoming = “”; // payload of packet

while (LoRa.available()) // can’t use readString() in callback
{
incoming += (char)LoRa.read(); // add bytes one by one
}

if (incomingLength != incoming.length()) // check length for error
{
Serial.println(“error: message length does not match length”);
return; // skip rest of function
}

// if the recipient isn’t this device or broadcast,
if (recipient != localAddress || sender != destination)
{
Serial.println(“This message is not for me.”);
return; // skip rest of function
}

// if message is for this device, or broadcast, print details:
Serial.println(“Received from: 0x” + String(sender, HEX));
Serial.println(“Sent to: 0x” + String(recipient, HEX));
Serial.println("Message length: " + String(incomingLength));
Serial.println("Message: " + incoming);
Serial.println("RSSI: " + String(LoRa.packetRssi()));
Serial.println("Snr: " + String(LoRa.packetSnr()));
Serial.println();
flagDataAvailable = 1;
dataReceived = incoming;
}

Tx code :

#include “heltec.h”
#include <ArduinoJson.h>
#define BAND 433E6 //you can set band here directly,e.g. 868E6,915E6
#include “DHT.h”
#define DHTPIN 22
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

byte localAddress = 1; // address of this device
byte destination = 0; // destination to send to
const int csPin = 18; // LoRa radio chip select
const int resetPin = 14; // LoRa radio reset
const int irqPin = 26;

boolean dataAvailableFlag=0;
void setup()
{
//WIFI Kit series V1 not support Vext control
Heltec.begin(true /DisplayEnable Enable/, true /Heltec.LoRa Disable/, true /Serial Enable/, true /PABOOST Enable/, BAND /long BAND/);
Serial.begin(9600); // initialize serial
pinMode(4,INPUT);
dht.begin();
LoRa.setPins(csPin, resetPin, irqPin);
LoRa.onReceive(onReceive);
LoRa.receive();
}

void loop()
{
if (dataAvailableFlag==1)
{
StaticJsonDocument<200>doc;
String testJson1;
doc[“NODE_ID”] =localAddress;
doc[“Temperature”] = dht.readTemperature();
doc[“Humidity”] = dht.readHumidity();
doc[“Smoke”] = digitalRead(4);
doc[“Rain”] = “0”;
serializeJson(doc, testJson1);
sendMessage(testJson1);
Serial.println("Sending " + testJson1);

localAddress=localAddress+1;
if (localAddress>8)
{localAddress=1;}

dataAvailableFlag=0;
LoRa.receive();

}
}

void sendMessage(String outgoing)
{
LoRa.beginPacket(); // start packet
LoRa.write(destination); // add destination address
LoRa.write(localAddress); // add sender address
LoRa.write(outgoing.length()); // add payload length
LoRa.print(outgoing); // add payload
LoRa.endPacket(); // finish packet and send it
}

void onReceive(int packetSize)
{
if (packetSize == 0)
{return ; // if there’s no packet, return
}

// read packet header bytes:
byte recipient = LoRa.read(); // recipient address
byte sender = LoRa.read(); // sender address
byte incomingLength = LoRa.read(); // incoming msg length

String incoming = “”; // payload of packet

while (LoRa.available()) // can’t use readString() in callback
{
incoming += (char)LoRa.read(); // add bytes one by one
}

// if the recipient isn’t this device or broadcast,
if (recipient != localAddress or sender != destination)
{
Serial.println(“This message is not for me.”);
return ; // skip rest of function
}
if (incomingLength != incoming.length()) // check length for error
{
Serial.println(“error: message length does not match length”);
return; // skip rest of function
}
// if message is for this device, or broadcast, print details:
Serial.println(“Received from: 0x” + String(sender, HEX));
Serial.println(“Sent to: 0x” + String(recipient, HEX));
Serial.println("Message length: " + String(incomingLength));
Serial.println("Message: " + incoming);
Serial.println("RSSI: " + String(LoRa.packetRssi()));
Serial.println("Snr: " + String(LoRa.packetSnr()));
Serial.println();
dataAvailableFlag=1;
}

[Xiao-H]

You can modify frequency by :
#define BAND 433E6 //you can set band here directly,e.g. 868E6,915E6

Did you buy 470MHz frequency band? If you want to send on 868MHz, You shoud buy the products of 868 MHz frequency band.

[Huisache]

How do you set set the localAddress of Sender and Receiver boards, for multi communication?
Thanks