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How to parse and read JSON file correctly?

Hi guys,

I am using the nRF52832 board and I want to parse and read my JSON file. I don't have too much experience working with cJSON and here you will find my simple code where I try to understand how to define things properly. I will appreciate a lot if you can help me with some advice or better if you can suggest me where I made errors.

Best regards,

Adnan.

/*
 * Copyright (c) 2012-2014 Wind River Systems, Inc.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <zephyr.h>
#include <sys/printk.h>
#include <string.h>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <float.h>
#include <limits.h>
#include <ctype.h>
#include "cJSON.h"


char *create_hello(void) {
	
	char *string;
	
	cJSON *hello = cJSON_CreateObject();
	
	cJSON *functionName = cJSON_CreateString("hello_world");
	cJSON_AddItemToObject(hello, "functionName", functionName);
	
	string = cJSON_Print(hello);
	
	cJSON_Delete(hello);
	return string;
	
	}

void hello_world (void) {
	
	printk("Hello World! %s\n", CONFIG_BOARD);
	}


void main(void)
{
	const char *hello = "{\"functionName\": \"hello_world\"}";
	cJSON *hello_json = cJSON_Parse(hello);
	cJSON *functionName = cJSON_GetObjectItemCaseSensitive(hello_json, "functionName");
	
	while(true){
		
		if (functionName == "hello_world") {
			hello_world();
			k_sleep(K_SECONDS(1));
			}		
			
		}
}

Parents
  • Hello, Aduka!

    Thank you for reaching out. First of all, have you defined the correct prj.conf for your application? Mine looks like this for the hello_world sample:

    # nothing here
    CONFIG_CJSON_LIB=y
    
    # newlibc
    CONFIG_NEWLIB_LIBC=y

    Secondly, your code is mostly correct, but you have done an illegal comparison in your while loop. Look at my main below, where the error is corrected:

    void main(void)
    {
    	const char *hello = "{\"functionName\": \"hello_world\"}";
    	cJSON *hello_json = cJSON_Parse(hello);
    	char* functionName = cJSON_Print(cJSON_GetObjectItemCaseSensitive(hello_json, "functionName"));
    	
    	while(true){
    		
    		if (strcmp(functionName, "hello_world")) {
    			hello_world();
    			k_sleep(K_SECONDS(1));
    			}		
    			
    		}
    }

    In the code above I have changed line 45 so that cJSON_Print is used to write the content to a string. Then I have changed 49 to use strcmp, for comparing the strings. The line numbers I reference are from your original code. 

    Hope this helps you on your way, and please reach out if you wonder about anything else. 

    Best regards,
    Carl Richard

  • Hi Carl,

    Thanks a lot for this help and suggestions! I tried this code with these corrections, but again I am not able to compile it on my board. Now the problem occurs in my proj.conf file I think.

    This is the error:

    error: Aborting due to Kconfig warnings

    CMake Error at /home/adnan/zephyrproject/zephyr/cmake/kconfig.cmake:217 (message):
    command failed with return code: 1
    Call Stack (most recent call first):
    /home/adnan/zephyrproject/zephyr/cmake/app/boilerplate.cmake:510 (include)
    /home/adnan/zephyrproject/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:24 (include)
    /home/adnan/zephyrproject/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:40 (include_boilerplate)
    CMakeLists.txt:5 (find_package)


    -- Configuring incomplete, errors occurred!
    See also "/home/adnan/zephyrproject/zephyr/build/CMakeFiles/CMakeOutput.log".
    See also "/home/adnan/zephyrproject/zephyr/build/CMakeFiles/CMakeError.log".
    FAILED: build.ninja
    /usr/bin/cmake --regenerate-during-build -S/home/adnan/zephyrproject/zephyr/samples/hello_world_cjson -B/home/adnan/zephyrproject/zephyr/build
    ninja: error: rebuilding 'build.ninja': subcommand failed
    FATAL ERROR: command exited with status 1: /usr/bin/cmake --build /home/adnan/zephyrproject/zephyr/build

    Can you maybe figure out what could be a potential problem now? And also, I forgot to tell that I use Zephyr if that is important for this problem. Also, my last question is related to Makefile and prj.conf files...where I can find the proper configuration for different samples. For sure, I will need to use cJSON together with my BLE example.

    Thanks in advance and best regards,

    Adnan.

  • Hi Carl,

    I deleted the whole Zephyr directroy and zephyr-sdk as well. I start from scratch again, but I am still not able to solve the problem related to nrf-sdk. This is the error that I get every time when I try to run this command west init -m github.com/.../sdk-nrf --mr v1.3.2:

    FATAL ERROR: already initialized in /home/adnan, aborting.

    I really don't know how to solve this problem and also I don't know what could be a problem if I removed everything and start from scratch. Also, the second problem is related to the installation of toolchain and required tools. When I install GNU Arm Embedded Toolchain how can I put it inside the folder ~/gnuarmemb if I don't have it at that time. Also, you referred to the Zephyr Getting Started Guidline. I need to follow these steps until Get Zephyr and install Python dependencies this part or even I need to install Zephyr inside the same directory as I did it before ~zephyrproject?

    Can you please help me to solve these issues because I am really quite confusing related to all these part and errors.

    Thanks a lot in advance and best regards,

    Adnan.

  • Hi again! I see! Seems like you are correct that you have to unset the ZEPHYR_BASE environment variable. How you do this depends on your operating system. What is your OS? Secondly, if you don't have the gnuarmemb directory you should create it, and then install the toolchain there. If you follow the NCS installation guide you will end up with a directory where all relevant repositories (including Zephyr) are present. The only thing you should need to do from the Zephyr Getting Started guide is to install the host dependencies, the rest is handled in the nRF Connect SDK installation guide.

    Most Python dependencies should be present from your previous Zephyr installation, but I recommend installing them as described anyways just to be sure. 

    I understand that this is troublesome. 

    Best regards,
    Carl Richard

  • Hi Carl,

    Thanks again for this help! I am using Ubuntu 18.04.5 LTS. Gnuarmemb is just the classic empty folder or what? That is what I am interested in...Is this folder at the end have to be in ncs directory or not? Related to this part with host dependencies I understood. I will try to follow all steps, but sometimes I just think that maybe you put some steps before the ones that should be on that place...if you understand me?

    Best regards,

    Adnan.

  • Hi again!

    In Ubuntu it should be enough to call "unset ZEPHYR_BASE" on the command line and restarting your shell. And yes, gnuarmemb is just an empty directory and it does not need to be in the NCS directory. We recommend the location "~/gnuarmemb".

    I understand you. It's a bit convoluted.

    Best regards,
    Carl Richard

  • Hi Carl,

    I tried to unset this variable, but there is still the same error when I try to run this command:

    west init -m github.com/.../sdk-nrf --mr v1.3.2

    Error:

    FATAL ERROR: already initialized in /home/adnan, aborting.

    Now I only see the chance to reboot the whole Ubuntu and start from scratch everything. Do you see
    any possible solution of this error?

    Best regards,

    Adnan.
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