ARDUINOJSON_ENABLE_PROGMEM

Enables the support of strings stored in program memory, ie in Flash.

The default is 1 of PROGMEM is defined, 0 otherwise.

How to force the value?

If you need to force the support of PROGMEM strings, add this at the top of your program:

#define ARDUINOJSON_ENABLE_PROGMEM 1
#include <ArduinoJson.h>

On the other hand, if you need to disable PROGMEM string, do:

#define ARDUINOJSON_ENABLE_PROGMEM 0
#include <ArduinoJson.h>

This is useful if your platform defines PROGMEM but doesn’t actually support Flash-stored strings.

Where a PROGMEM string can be used?

Once enabled, you can use a PROGMEM string in many places.

You can use a PROGMEM string as your JSON input

 // WARNING: the content of the PROGMEM string will be duplicated in the JsonBuffer.
 JsonObject& root = jsonBuffer.parseObject(F("{\"sensor\":\"gps\",\"time\":1351824120,"
                            "\"data\":[48.756080,2.302038]}"));

You can use a PROGMEM string to get an element of a JsonObject
```
 long time = root[F("time")];
```

You can use a PROGMEM string to set an element of a JsonObject

 // WARNING: the content of the PROGMEM string will be duplicated in the JsonBuffer.
 root[F("time")] = time;

You can set a JsonObject (or JsonArray) element to a PROGMEM string:

 // WARNING: the content of the PROGMEM string will be duplicated in the JsonBuffer.
 root["sensor"] = F("gps");

You can compare the content of a JsonObject with a PROGMEM string

 if (root["sensor"] == F("gps")) {
     // ...
 }