Adrian replied to the topic 'Weather radio don't want connect' in the forum. 8 months ago

Slight progress

There is a clue to setting the Static JsonDocument in the webpages

arduinojson.org/v6/assistant/

I set mine to 194 to allow for the JSON data and the strings
How to work this out on the fly for different sensor and outputs?

The main problem with the outputting is with serializeJsonPretty, this puts out a very long output with all those nice spaces and ^M at the end.
This seems to overrun the memory which is put into String result="";
I am not sure how the String object looks after its memory, or if you have to reserve memory for it yourself, and free it up afterwards etc.

You can specify how much to output in the serialze functions

I tried to output to a buffer and set a size limit on this

#include <ArduinoJson.h>
#define DESTBUFSIZE 320
char destBuf[DESTBUFSIZE];

#ifdef __arm__
// should use uinstd.h to define sbrk but Due causes a conflict
extern "C" char* sbrk(int incr);
#else  // __ARM__
extern char *__brkval;
#endif  // __arm__

int freeMemory() {
  char top;
#ifdef __arm__
  return &top - reinterpret_cast<char*>(sbrk(0));
#elif defined(CORE_TEENSY) || (ARDUINO > 103 && ARDUINO != 151)
  return &top - __brkval;
#else  // __arm__
  return __brkval ? &top - __brkval : &top - __malloc_heap_start;
#endif  // __arm__
}

In the getSensorData I changed it to use the buffer and permitted length.
void getSensorData(bool pretty) {

and

  int ret;

  destBuf[0] = 0;// Null terminator

  if (pretty)
    ret = serializeJsonPretty(weatherDoc, destBuf, DESTBUFSIZE);
  else
    ret = serializeJson(weatherDoc, destBuf, DESTBUFSIZE);

  Serial.print("ret :"); Serial.println(ret);
  Serial.print("Free Memory: "); Serial.println(freeMemory());
  Serial.print("DestBuf :"); Serial.println(destBuf);

Then in the w and p commands
    case 'w':
      //Serial.println(getSensorData(false));
      getSensorData(false);
      Serial.println(destBuf);
      break;
    case 'c':
      Serial.println(getCurrentConfig());
      break;
    case 'p':
      //Serial.println(getSensorData(true));
      getSensorData(true);
      Serial.println(destBuf);
      break;

Not sure if this is the best approach. I do remember trying to understand the firmata stuff on the old meteostation and wringing my hands.

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