Mqtt simple nrf9160, send JSON as utf-8

[David]

Hi,

I have configured the MQTT simple sample from nordic to send data to our broker, this works just fine at the moment.

I would like to send Json formated data to the broker ----->

{
"sensor_id": "c5278fbf-c6d5-4c48-b51d-652beb609b34",
"value": 13.0
}

When I subscribe to topic, I only see "{" as incoming data.

How can I make sure that the Json data is correctly formated i code ?

Any assistance would be appreciated.

I am using the <cJSON.h> library.

char field_name[80], value[80], *out;
                cJSON *root,*car;



                //char str1[80] = "{'sensor_id:' 'c5278fbf-c6d5-4c48-b51d-652beb609b34','value:' 13.0}";

                root  = cJSON_CreateObject();
                car=  cJSON_CreateArray();

                cJSON_AddItemToObject(root, "sensor_id", cJSON_CreateString("c5278fbf-c6d5-4c48-b51d-652beb609b34"));
                cJSON_AddItemToObject(root, "value", cJSON_CreateString("12"));
                cJSON_AddItemToArray(car, root);

                out = cJSON_Print(root);
                printk(out);
                //char out1 = {"sensor_id"":""c5278fbf-c6d5-4c48-b51d-652beb609b34","value"":""13.0"};
                k_sleep(K_MSEC(5000));
                data_publish(&client, MQTT_QOS_1_AT_LEAST_ONCE, car, sizeof(car));
                k_sleep(K_MSEC(5000));

David

[Carl Richard]

Hello, David!

I managed to publish and receive jSON data using the following code: 

static void transmit() {
   char *out;
   char *id1 = "c5278fbf-c6d5-4c48-b51d-652beb609b34"; 
   char *id2 = "c5278fgf-c6d5-4c48-b51d-652beb6s9b34"; 
   char *value1 = "13.0";
   char *value2 = "117.0";
   cJSON *root, *sensors, *sensor;

   /* create root node and array */
   root = cJSON_CreateObject();
   sensors = cJSON_CreateArray();

   /* add sensors array to root */
   cJSON_AddItemToObject(root, "sensors", sensors);

   /* add 1st sensor to sensors array */
   cJSON_AddItemToArray(sensors, sensor = cJSON_CreateObject());
   cJSON_AddItemToObject(sensor, "value", cJSON_CreateString(value1));
   cJSON_AddItemToObject(sensor, "sensor_id", cJSON_CreateString(id1));

   /* add 1st sensor to sensors array */
   cJSON_AddItemToArray(sensors, sensor = cJSON_CreateObject());
   cJSON_AddItemToObject(sensor, "value", cJSON_CreateString(value2));
   cJSON_AddItemToObject(sensor, "sensor_id", cJSON_CreateString(id2));

   /* print everything */
   out = cJSON_Print(root);
   printk("%s\n", out);

   /* Publish with MQTT */
   data_publish(&client, MQTT_QOS_1_AT_LEAST_ONCE,
				out, strlen(out));

   free(out);

   /* free all objects under root and root itself */
   cJSON_Delete(root);

   return;
}

Could you try to adapt this to your use? 

Edit: code is based on the following stack overflow ticket.

Best regards,
Carl Richard