How do I use the cJSON library?

[June6]

I need to use cJSON to parse the uart data. I found the file in SDK15.3 but how can I use the related function?

[Dmitry]

Hi,

just add sources and headers to your project and call functions as usual... you also need to add mem_manager library from SDK. cJSON has a good README with detailed instructions how to use this library.

[June6]

Is there a routine example of how to use the memory management library?

[Dmitry]

I tried to set XXS and XXL to 500 and 300, everything is fine.. I can suppose that you have block sizes not ailgned to 4 (some instructions require word-aligned operands).

June6 said:

I don't know how to display debug traces (disassembly, stack, registers) where hard faults occur. 

Keil debugger shows everything if you run program under debug session.

[June6]

The memory block size needs to be a multiple of 4?

[Dmitry]

Standard malloc always allocates a word-aligned block. nrf_malloc will allocate a new block starting from next byte, so if your block size is not word-aligned, allocations will be unaligned too.

[June6]

Byte alignment of memory! ! ! I know this concept until now. It’s true that the memory block size is set to a multiple of 4 and the problem disappears. 

[June6]

So, my understanding is that the byte alignment principle is followed when using malloc or nrf_malloc, and the memory address is aligned in 4 bytes. Is my understanding correct?

[Dmitry]

June6 said:

when using malloc

June6 said:

nrf_malloc, and the memory address is aligned in 4 bytes

You mean block size? Yes, in both cases you'll get a word-aligned address.

[June6]

all right. I got it. Thanks Dmitry!!! I will continue my project.