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Mqtt extra characters

Good afternoon, I use your gateway. It’s very cool in features. Thank you for your work.
I have a problem with receiving messages from the mqtt topic. The fact is that the message comes in the form of incorrect JSON. You can see the signs ("), () at the beginning and end of the message.

What could be the problem?
I use JSON in the transmitter.

StaticJsonBuffer<BUFFER_SIZE> jsonBuffer;

JsonObject& root = jsonBuffer.createObject();
root[“hum”] = humValue;
root[“pres”] = presValue;
root[“temp”] = tempValue;

char buffer[root.measureLength() + 1];
root.printTo(buffer, sizeof(buffer));

radio.sendWithRetry(RECEIVER, buffer, sizeof(buffer));

Buffer port arduino {“hum”:43.41,“pres”:736.0,“temp”:13.58}

Any ideas how to fix this?


yes it seems that your json object is an assembly of two objects but not with the good way.
You should create a nested object to have a valid json.

this did not work, note the double quotes at the beginning and end of the line, this is not a valid JSON structure.
Do I need to make settings in the gateway?

payload : "{"data":"{\"Weather\":\"node1\",\"Value\":{\"hum\":60.00977,\"pres\":739.5559,\"t","rssi":-48,"senderid":1}"

Could you post your code (zgatewayrfm69.ino) and well formated please.

 #ifdef ZgatewayRFM69

 #include <RFM69.h>                //
 #include <SPI.h>
 #include <EEPROM.h>

 char RadioConfig[128];

 // vvvvvvvvv Global Configuration vvvvvvvvvvv

 struct _GLOBAL_CONFIG {
  uint32_t    checksum;
  char        rfmapname[32];
  char        encryptkey[16+1];
  uint8_t     networkid;
  uint8_t     nodeid;
  uint8_t     powerlevel; // bits 0..4 power leve, bit 7 RFM69HCW 1=true
  uint8_t     rfmfrequency;

#define GC_POWER_LEVEL    (pGC->powerlevel & 0x1F)
#define GC_IS_RFM69HCW  ((pGC->powerlevel & 0x80) != 0)
#define SELECTED_FREQ(f)  ((pGC->rfmfrequency==f)?"selected":"")


// vvvvvvvvv Global Configuration vvvvvvvvvvv
uint32_t gc_checksum() {
  uint8_t *p = (uint8_t *)pGC;
  uint32_t checksum = 0;
  p += sizeof(pGC->checksum);
  for (size_t i = 0; i < (sizeof(*pGC) - 4); i++) {
    checksum += *p++;
  return checksum;

#if defined(ESP8266) || defined(ESP32)
void eeprom_setup() {
  pGC = (struct _GLOBAL_CONFIG *)EEPROM.getDataPtr();
  // if checksum bad init GC else use GC values
  if (gc_checksum() != pGC->checksum) {
    trc(F("Factory reset"));
    memset(pGC, 0, sizeof(*pGC));
    strcpy_P(pGC->encryptkey, ENCRYPTKEY);
    strcpy_P(pGC->rfmapname, RFM69AP_NAME);
    pGC->networkid = NETWORKID;
    pGC->nodeid = NODEID;
    pGC->powerlevel = ((IS_RFM69HCW)?0x80:0x00) | POWER_LEVEL;
    pGC->rfmfrequency = FREQUENCY;
    pGC->checksum = gc_checksum();

RFM69 radio;

void setupRFM69(void) {
  #if defined(ESP8266) || defined(ESP32)
  int freq;
  static const char PROGMEM JSONtemplate[] =
  char payload[128];

  radio = RFM69(RFM69_CS, RFM69_IRQ, GC_IS_RFM69HCW, RFM69_IRQN);

  // Initialize radio
  if (!radio.initialize(pGC->rfmfrequency, pGC->nodeid, pGC->networkid))
    trc(F("ZgatewayRFM69 initialization failed"));

  if (GC_IS_RFM69HCW) {
    radio.setHighPower();    // Only for RFM69HCW & HW!
  radio.setPowerLevel(GC_POWER_LEVEL); // power output ranges from 0 (5dBm) to 31 (20dBm)

  if (pGC->encryptkey[0] != '\0') radio.encrypt(pGC->encryptkey);

  trc(F("ZgatewayRFM69 Listening and transmitting at"));
  switch (pGC->rfmfrequency) {
    case RF69_433MHZ:
      freq = 433;
    case RF69_868MHZ:
      freq = 868;
    case RF69_915MHZ:
      freq = 915;
    case RF69_315MHZ:
      freq = 315;
      freq = -1;

  size_t len = snprintf_P(RadioConfig, sizeof(RadioConfig), JSONtemplate,
      freq, GC_IS_RFM69HCW, pGC->networkid, GC_POWER_LEVEL);
  if (len >= sizeof(RadioConfig)) {
    trc(F("\n\n*** RFM69 config truncated ***\n"));

boolean RFM69toMQTT(void) {
  //check if something was received (could be an interrupt from the radio)
  if (radio.receiveDone())
    trc(F("Creating RFM69 buffer"));
    StaticJsonBuffer<JSON_MSG_BUFFER> jsonBuffer;
    JsonObject& RFM69data = jsonBuffer.createObject();
    uint8_t data[RF69_MAX_DATA_LEN+1]; // For the null character
    uint8_t SENDERID = radio.SENDERID;
    uint8_t DATALEN = radio.DATALEN;
    uint16_t RSSI = radio.RSSI;

    //save packet because it may be overwritten
    memcpy(data, (void *)radio.DATA, DATALEN);
    data[DATALEN] = '\0';  // Terminate the string

    // Ack as soon as possible
    //check if sender wanted an ACK
    if (radio.ACKRequested())
    //updateClients(senderId, rssi, (const char *)data);

    trc(F("Data received"));
    trc((const char *)data);

    char buff[sizeof(subjectRFM69toMQTT)+4];
    sprintf(buff, "%s/%d", subjectRFM69toMQTT, SENDERID);
    RFM69data.set("data", (char *)data);
    RFM69data.set("rssi", (int)radio.RSSI); 
    RFM69data.set("senderid", (int)radio.SENDERID);

    return true;

  } else {
    return false;

#ifdef simpleReceiving
  void MQTTtoRFM69(char * topicOri, char * datacallback) {

    if(strstr(topicOri, subjectMQTTtoRFM69) != NULL){
      trc(F("MQTTtoRFM69 data analysis"));
      char data[RF69_MAX_DATA_LEN+1];
      memcpy(data, (void *)datacallback, RF69_MAX_DATA_LEN);
      data[RF69_MAX_DATA_LEN] = '\0';
      //We look into the subject to see if a special RF protocol is defined
      String topic = topicOri;
      int valueRCV = defaultRFM69ReceiverId; //default receiver id value
      int pos = topic.lastIndexOf(RFM69receiverKey);
      if (pos != -1){
        pos = pos + +strlen(RFM69receiverKey);
        valueRCV = (topic.substring(pos,pos + 3)).toInt();
        trc(F("RFM69 receiver ID:"));
      if(radio.sendWithRetry(valueRCV, data, strlen(data),10)) {
        trc(F(" OK "));
        // Acknowledgement to the GTWRF topic
        char buff[sizeof(subjectGTWRFM69toMQTT)+4];
        sprintf(buff, "%s/%d", subjectGTWRFM69toMQTT, radio.SENDERID);
        pub(buff, data);
      } else {
        trc(F("RFM69 sending failed"));
#ifdef jsonReceiving
  void MQTTtoRFM69(char * topicOri, JsonObject& RFM69data) {
   if (strcmp(topicOri,subjectMQTTtoRFM69) == 0){
      const char * data = RFM69data["data"];
      trc(F("MQTTtoRFM69 json data analysis"));
        trc(F("MQTTtoRFM69 data ok"));
        int valueRCV = RFM69data["receiverid"]| defaultRFM69ReceiverId; //default receiver id value
        trc(F("RFM69 receiver ID:"));
        if(radio.sendWithRetry(valueRCV, data, strlen(data),10)) {
          trc(F(" OK "));
          // Acknowledgement to the GTWRF topic
          pub(subjectGTWRFM69toMQTT, RFM69data);// we acknowledge the sending by publishing the value to an acknowledgement topic, for the moment even if it is a signal repetition we acknowledge also
        } else {
          trc(F("MQTTtoRFM69 sending failed"));
        trc(F("MQTTtoRFM69 Fail reading from json"));
#endif`Preformatted text``Preformatted text`

no solution to my problem? maybe there is another way how to transfer transfer to the gateway

I would try first to send a simple sentence as “data” and see if it pass.


Indeed the pub method is used by all the gateway on the same principle as ZgatewayRFM69 do, I don’t think the issue comes from it.

Once a simple data pass by the gateway, you could see how to build an imbricated json like this one:


I have a lot of time to send data from my BME280.
I did sending simple data.
and got the output {"data":"7","rssi":-57,"senderid":1}
As you can see, the number 7 will remain in double quotes, which means that it is a string, not a value. I still did not understand how to transfer data to me. If anyone has an example of transmitting data from a BME280 sensor through a gateway, I would be very grateful.


This is due to the fact that data is a char :
RFM69data.set("data", (char *)data)

If you want to handle integer you have to declare it and set if into the RFM69 json :

int mydata = 3 ; 
RFM69data.set("mydata", (int)mydata) ;