Sending a message containing double quotes with Lora.print

[jerome-angeloni]

Hi,

I have a working setup with 2 TTGO LORA boards. On the TX side, I'm using this library for sending a message. I can send this message {Air_temp: 25, Water_temp: 22}, and it is correctly received. But actually I need to send {"Air_temp": 25, "Water_temp": 22}. For this I'm using the backslash escape character in front of the double quotes, but the print method does not detect the escape character and prints : {\"Air_temp\": 25, \"Water_temp\": 22}.

I've looked at the library code but can't find where the Lora.print function is defined. Can someone help? thanks!

[IoTThinks]

The library sends and receives data as bytes. It doesn't care about backslash. Backslash is just a byte. Then you cast it as a char or a number or a string depending on how you want to see.

[IoTThinks]

To send it as {"Air_temp": 25, "Water_temp": 22} LoRa.print("{\"Air_temp\": 25, \"Water_temp\": 22}");

[jerome-angeloni]

One more information: on the RX side, I run OpenMQTTGateway and I check the result in the MQTT broker logs: 1 - LoRa.print(0x22); gives in MQTT logs: { "rssi" : -47, "snr" : 9.75, "pferror" : 9068, "packetSize" : 2, "message" : "34" }

2 - LoRa.print(char(0x22)); gives in MQTT logs: { "rssi" : -64, "snr" : 8.5, "pferror" : 9017, "packetSize" : 1, "message" : "\ "" (I have to manually add a space here, else the rendering on this web page removes the backslash. in real life, in mqtt, I get doublequote,backslash,doublequote,doublequote) }

3 - LoRa.print("\ ""); gives in MQTT logs: { "rssi" : -45, "snr" : 9.25, "pferror" : 9068, "packetSize" : 1, "message" : "\ "" (I have to manually add a space here, else the rendering on this web page removes the backslash. in real life, in mqtt, I get doublequote,backslash,doublequote,doublequote) }

I can't find a way to get something like: "message" : """ (of course this is not the final objective, I'm just simplifying to the max for debug purpose)

[IoTThinks]

It is not relevant to the library anyway. Everything is built from bytes.

It is you or your application to define how you view the bytes.

[jerome-angeloni]

Thanks for looking into this. Finally I've found a workaround so I don't have to handle the double quotes (I tried but couldn't find something working because of C strings and String object in Arduino. There must be a way, but I found way of doing which brings the same results in HA): On the TX side:

 LoRa.beginPacket();
  LoRa.print(Air_Temp);
  LoRa.print("-");
  LoRa.print(Water_Temp);
LoRa.endPacket();

On the RX side:

    String packet;
    String air_temp;
    String water_temp;
    packet = "";
    air_temp="";
    water_temp="";
    for (int i = 0; i < packetSize; i++) {
      packet += (char)LoRa.read();
    }
    air_temp = packet.substring(0, 5);
    water_temp = packet.substring(6, 12);  //always the same size anyway
    LORAdata.set("air_temp", (char*)air_temp.c_str());
    LORAdata.set("water_temp", (char*)water_temp.c_str());

In HA configuration.yaml: sensor:

  - platform: mqtt
    name: Température Eau Piscine
    state_topic: "Lora/OpenMQTTGateway/LORAtoMQTT"
    unit_of_measurement: "°C"
    value_template: "{{ value_json.water_temp }}"
  - platform: mqtt
    name: Température Extérieure Piscine
    state_topic: "Lora/OpenMQTTGateway/LORAtoMQTT"
    unit_of_measurement: "°C"
    value_template: "{{ value_json.air_temp }}"

[IoTThinks]

Glad that it works for you. For me, I still send json strings with double quotes with no issue. RX side needs to use ArduinoJson to parse the json.

Btw, keep the LoRa messages as short as possible.