Particle.variable & JSON

Firmware
1

I’m still learning what are the best practices for good code but can someone tell me if this is a good approach or not. I currently have multiple variables returning a single value and I want combine them to a JSON format and just have one Particle.variable that would return all the data.
Sample code below is.

String Data;
char buf[256];

int a 
int b 

void setup()
{
  Particle.variable("JSON", Data);
}


void loop()
{  

JSONBufferWriter writer(buf, sizeof(buf));
writer.beginObject();
    writer.name("a").value(A);
    writer.name("b").value(B);
writer.endObject();
writer.buffer()[std::min(writer.bufferSize(), writer.dataSize())] = 0;

 Data = buf;
 
 }
 
 
 int enableAlerts(String command)
{

    if (command.equalsIgnoreCase("1"))
    {
        A = 1;
     
        EEPROM.put(setAlertEEPROMLocation, A);

        return 1;
    }
    else
    {

        A = 0;
       
        EEPROM.put(setAlertEEPROMLocation, A);

        return 0;
    }
}


int enablePhonePowerAlerts(String command)
{

    if (command.equalsIgnoreCase("1"))
    {
        B = 1;
   
        EEPROM.put(setAlertPhonePowerEEPROMLocation, B);

        return 1;
    }
    else
    {

        B = 0;
       
        EEPROM.put(setAlertPhonePowerEEPROMLocation, B);

        return 0;
    }
}
2

I don’t think you need your String Data variable, you can just use bufas the base variable for your Particle.variable().

You are also using variables A & B but you only seem to have a & b defined. C/C++ is case sensitive.

While your use of JSONBufferWriter() seems OK, I’d find it overkill for only a variable list that short.
Alternatively you could it do in a one-liner like this

  snprintf(buf, sizeof(buf), " \"a\":%d, \"b\":%d ", a, b);

You’d also only need to update buf when a or b actually have changed.

3

Thanks @ScruffR

Yes, that was a typo.

I do have more variables that are in the JSON return. I included just two as a example but I’ll see how snprintf works too.

Is it ok to place the JSONBufferWriter code in the loop section or could that be a concern? A or b values do currently update anytime there is a change

4

You can use JSONBufferWriter inside loop() but as for this

Even in that case you wouldn't need to update the JSON on each iteration of loop() but you could add a "dirty" flag that is set whenever one of the "monitored" variable gets changed and then update the JSON depending on that flag.

5

Cool. That makes sense. Thanks again!

6

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