The serialization results incorrect

[highfield]

I experience a wrong serialization by using such a snippet:

//
// Step 1: Reserve memory space
//
StaticJsonBuffer<200> jsonBuffer;

//
// Step 2: Build object tree in memory
//
JsonObject& root = jsonBuffer.createObject();
root["sensor"] = "gps";
root["time"] = 1351824120;

JsonArray& data = root.createNestedArray("data");
//data.add(48.756080, 6);  // 6 is the number of decimals to print
//data.add(2.302038, 6);   // if not specified, 2 digits are printed
{
  JsonObject& jsens = data.createNestedObject();
  jsens["name"] = "tizio";
  jsens["value"] = true;
}
{
  JsonObject& jsens = data.createNestedObject();
  jsens["name"] = "caio";
  jsens["value"] = 3.141519;
}

//
// Step 3: Generate the JSON string
//
root.printTo(Serial);

The resulting JSON is the following:

{"sensor":"gps","time":1351824120,"data":[{"name":"tizio"}]}

Is it me?

[highfield]

UPDATE.
I figured out the reason, and it seems on the (huge) memory usage. I'm using a 32-bit board and the buffer must be sized way longer than expected.
By running this snippet (notice the buffer size!)...

//
// Step 1: Reserve memory space
//
StaticJsonBuffer<1024> jsonBuffer;

//
// Step 2: Build object tree in memory
//
JsonObject& root = jsonBuffer.createObject();
root["sensor"] = "gps";
root["time"] = 1351824120;

JsonArray& data = root.createNestedArray("data");
//data.add(48.756080, 6);  // 6 is the number of decimals to print
//data.add(2.302038, 6);   // if not specified, 2 digits are printed

for (int i=0; i<100; i++)
{
  JsonObject& jsens = data.createNestedObject();
  jsens.add("name", "tizio");
  jsens.add("value", i);
}

//
// Step 3: Generate the JSON string
//
root.printTo(Serial);

...the result is the following (290 chars):

{"sensor":"gps","time":1351824120,"data":[{"name":"tizio","value":0},{"name":"tizio","value":1},{"name":"tizio","value":2},{"name":"tizio","value":3},{"name":"tizio","value":4},{"name":"tizio","value":5},{"name":"tizio","value":6},{"name":"tizio","value":7},{"name":"tizio","value":8},{}]}

I simply underestimated the actual usage of ram.

[bblanchon]

Yes, memory usage is almost 4 times bigger in 32-bit than in 8-bit.
To write platform independent code, I recommend using the following macros:

• JSON_ARRAY_SIZE(N) which returns the size of an array of N elements
• JSON_OBJECT_SIZE(N) which returns the size of an object of N key-value pairs

In your second last example, it could be:

JSON_OBJECT_SIZE(3)+JSON_ARRAY_SIZE(100)+100*JSON_OBJECT_SIZE(2)

Also, if you're not working in an embedded environment, you can switch to DynamicJsonBuffer which will automatically grow.

[highfield]

I'll bear in mind, thank you very much for the help.

Oh, you were mentioned:
https://highfieldtales.wordpress.com/2014/12/29/azure-veneziano-linkit-one/

[bblanchon]

Hey hey.
Congratulations for your project 👍