Working with json on the Host using Notecard Arduino lib does not work as expected

Tools & SDKs
1

Hi All,

Any ideas why out would ne NULL in this simple test ?

  char *test = "{\"num\": 1}";
  J *jsn = JParse(test);
  
  char *out = JPrintUnformatted(jsn);

  if (out != NULL) {
    serialDebug.println(out);
  } else {
    serialDebug.println("json serialize error");
  }

Thanks,
Serge

2

Strangely the following test modified to work with the original cJSON library works just fine but does not work with the cJSON shipped with Notecard Arduino Lib. I am testing with a Swan

#include <Notecard.h>

#define serialDebug SerialUSB
static const size_t MAX_SERIAL_WAIT_MS = 10000;

J *root = NULL;
J *nmeaParseErrors = NULL;

void setup() {
  serialDebug.begin(115200);
  size_t begin_serial_wait_ms = ::millis();
  while (!serialDebug && (MAX_SERIAL_WAIT_MS > (::millis() - begin_serial_wait_ms))) {
    ; // wait for serial port to connect. Needed for native USB
  }

  root = JCreateObject();

  JAddTrueToObject(root, "boolean");
  JAddStringToObject(root, "string", "test string");
  JAddObjectToObject(root, "obj");

  nmeaParseErrors = JAddArrayToObject(root, "errorList"); 

  J *oo = JCreateObject();
  JAddNumberToObject(oo, "count", 5.0);
  JAddNumberToObject(oo, "errorCode", 1.0);
  
  JAddItemToArray(nmeaParseErrors, oo); 

}

void loop() {
  serialDebug.println(JVersion());
  serialDebug.println(JPrintUnformatted(root));

  delay(5000);
}

cJSON version


#include <cJSON.h>

#define serialDebug SerialUSB
static const size_t MAX_SERIAL_WAIT_MS = 10000;

cJSON *root = NULL;
cJSON *nmeaParseErrors = NULL;

void setup() {
  serialDebug.begin(115200);
  size_t begin_serial_wait_ms = ::millis();
  while (!serialDebug && (MAX_SERIAL_WAIT_MS > (::millis() - begin_serial_wait_ms))) {
    ; // wait for serial port to connect. Needed for native USB
  }

  root = cJSON_CreateObject();

  cJSON_AddTrueToObject(root, "boolean");
  cJSON_AddStringToObject(root, "string", "test string");
  cJSON_AddObjectToObject(root, "obj");

  nmeaParseErrors = cJSON_AddArrayToObject(root, "errorList"); 

  cJSON *oo = cJSON_CreateObject();
  cJSON_AddNumberToObject(oo, "count", 5.0);
  cJSON_AddNumberToObject(oo, "errorCode", 1.0);
  
  cJSON_AddItemToArray(nmeaParseErrors, oo); 

}

void loop() {
  serialDebug.println(cJSON_Version());
  serialDebug.println(cJSON_PrintUnformatted(root));

  delay(5000);
}
3

Hi there @ssozonoff!

This does seem strange! Many thanks for providing a SSCCE. I’ll take it for a spin and see if I can reproduce the problem.

4

I’ve reproduced your issue. I’ll try to find the root cause.

5

Great that you were able to reproduce this, thanks for having a look into it.

6

Hi there again @ssozonoff!

So, the quick fix is to instantiate Notecard and call Notecard::begin() or one of its overloads. This is necessary to initialize some internals before cjson will work.

Can I ask, what’s your use case for using cjson without the Notecard?

7

Hi Mat,

Thanks for your reply. The reason for doing this was actually to test the construction of some Json structures on a standalone host (Swan) since my actual setup is outside :slight_smile:

Thanks,
Serge

8

Ah, gotcha! Makes sense. Does using Notecard::begin() work for you in this scenario?

9

Yes it does. Thanks!

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