How to get data from sensors separately in the Lora receiver??

[Calamardin]

Hello everyone, I have a question about how to separately obtain the data sent by various sensors and then assign them to different variables. Yes, for example I put a temperature sensor and a gas sensor in the same package and send it (I include a small code fragment in the transmitter)

LoRa.print(mySensor.CO2);
LoRa.print(",");
LoRa.print(mySensor.TVOC);
LoRa.print(",");
And in the receiver I get everything together with the following instructions:

void onReceive(int packetSize) {

for (int i = 0; i < packetSize; i++) {

Serial.print((char)LoRa.read());
How can I get the CO2 value on the one hand, the temperature on the other, etc. to assign each value to a variable and then use it, for example, to send it via mqtt?

Thanks in advance

[Kongduino]

First, you should use a data format like Cayenne LPP. The examples in this library are for LoRaWAN, but the principle is the same, regardless of how you send the data. The decode example show how to transform a Cayenne data packet into a JSON object.

[Calamardin]

thank you very much for your help. Will try as soon as I can.
regards

[miroan81]

In case anyone is having the same question send your data like this separated by comma

21.70 , 42.39 , 0.10 , 0.05 , 0.00 , 0 , 0 , 7.44 , 22.10 , 153

Then split the string in how much parts you need

`
while (LoRa.available()) {
String LoRaData = LoRa.readString();
Serial.print(LoRaData);

  int pos[10];
  int count = 0;
  for (int i = 0; i < LoRaData.length(); i++) {
    if (LoRaData.charAt(i) == ',') {
      pos[count] = i;
      count++;
    }
  }
  String part1 = LoRaData.substring(0, pos[0]);
  String part2 = LoRaData.substring(pos[0] + 1, pos[1]);
  String part3 = LoRaData.substring(pos[1] + 1, pos[2]);
  String part4 = LoRaData.substring(pos[2] + 1, pos[3]);
  String part5 = LoRaData.substring(pos[3] + 1, pos[4]);
  String part6 = LoRaData.substring(pos[4] + 1, pos[5]);
  String part7 = LoRaData.substring(pos[5] + 1, pos[6]);
  String part8 = LoRaData.substring(pos[6] + 1, pos[7]);
  String part9 = LoRaData.substring(pos[7] + 1, pos[8]);
  String part10 = LoRaData.substring(pos[8] + 1);`

[Kongduino]

This would be a very wasteful way of sending data... And it wouldn't work with your example, what with the spaces around the commas... A much MUCH better way would be to pack the floats into a buffer, and send the bytes. On the other side you unpack the data.

Consider this simple code:

#include <stdio.h>
#include <string.h>

int main(int argc, char** argb) {
  float a, b;
  printf("Size of float: %lu\n\n", sizeof(a));
  union twoFloats {
    struct {
      float numberA, numberB;
    };
    char bytes[8];
  };
  a = 3.14;
  b = a * 2;
  union twoFloats tf0, tf1;
  printf("Size of union: %lu\n\n", sizeof(tf0));
  tf0.numberA = a;
  tf0.numberB = b;
  printf("A = %.2f, B = %.2f\n", tf0.numberA, tf0.numberB);
  memcpy(tf1.bytes, tf0.bytes, 8);
  printf("A = %.2f, B = %.2f\n", tf1.numberA, tf1.numberB);
  return 0;
}

Packing and unpacking the floats is easy and doesn't require much processing – and is foolproof. I put only two here, but I could have put ten. Just make the array bytes big enough (4 x 10 = 40 bytes). No parsing, no tokenizing, no string-to-float conversion. ie less power consumption, which is always important in IOT, especially with LoRa-enabled devices.

But that's a moot point – as I mentioned in my answer above, CayenneLPP does it all for you. But your "solution" is definitely not it...

[miroan81]

I left spaces just for debugging purposes, it was easier to read, that has been removed. The code is working great so far for the past week or so, yeah I hat to convert string to float to make db happy but that's it, I had no other issues.
TBH I wanted to avoid JSON and adding extra libraries but I'll definitely look in to it and your code above, thank you!