CODEWITHSUNDEEP
cmemoryembeddedbuffer
user2665581
user2665581

Reputation: 75

Memory not allocating (Embedded uC MSP430)

I'm using an MSP430G2553 microcontroller (500 bytes of SRAM and 16kB of flash). I have 4 ring buffers allocating memory at the initialization of my code (using malloc)

typedef struct
{
    unsigned char Head;
    unsigned char Tail;
    unsigned char Size;
    unsigned char *Buffer;
} RingBuffer;

void RB_Init(RingBuffer *RB)
{
    RB->Size = 32;
    RB->Tail = 0;
    RB->Head = 0;
    RB->Buffer = (unsigned char*) malloc(RB->Size);
}

Basically I'm calling RB_Init four times to create those ring buffers. When the size (capacity of the ring buffer) is 16 everything is fine and I check all four and they each have a memory address. When I change the size to 32 only 2 get memory addresses, the last two aren't getting memory allocated.

Based on the memory map I get from code composer studio (shown below) it looks like I still have a lot of space (under RAM and FLASH). Why aren't the last two buffer arrays getting addresses when I have the sizes at 32 bytes (Why does it seem I hit my limit at 64 bytes?)

******************************************************************************
                  MSP430 Linker PC v4.1.5                      
******************************************************************************
>> Linked Fri Dec 27 22:53:28 2013

OUTPUT FILE NAME:   <xxx.out>
ENTRY POINT SYMBOL: "_c_int00"  address: 0000c672


MEMORY CONFIGURATION

         name            origin    length      used     unused   attr    fill
----------------------  --------  ---------  --------  --------  ----  --------
  SFR                   00000000   00000010  00000000  00000010  RWIX
  PERIPHERALS_8BIT      00000010   000000f0  00000000  000000f0  RWIX
  PERIPHERALS_16BIT     00000100   00000100  00000000  00000100  RWIX
  RAM                   00000200   00000200  000000cf  00000131  RWIX
  INFOD                 00001000   00000040  00000000  00000040  RWIX
  INFOC                 00001040   00000040  00000000  00000040  RWIX
  INFOB                 00001080   00000040  00000000  00000040  RWIX
  INFOA                 000010c0   00000040  00000000  00000040  RWIX
  FLASH                 0000c000   00003fe0  00000802  000037de  RWIX
  INT00                 0000ffe0   00000002  00000000  00000002  RWIX
  INT01                 0000ffe2   00000002  00000000  00000002  RWIX
  INT02                 0000ffe4   00000002  00000002  00000000  RWIX
  INT03                 0000ffe6   00000002  00000002  00000000  RWIX
  INT04                 0000ffe8   00000002  00000000  00000002  RWIX
  INT05                 0000ffea   00000002  00000000  00000002  RWIX
  INT06                 0000ffec   00000002  00000002  00000000  RWIX
  INT07                 0000ffee   00000002  00000002  00000000  RWIX
  INT08                 0000fff0   00000002  00000000  00000002  RWIX
  INT09                 0000fff2   00000002  00000002  00000000  RWIX
  INT10                 0000fff4   00000002  00000000  00000002  RWIX
  INT11                 0000fff6   00000002  00000000  00000002  RWIX
  INT12                 0000fff8   00000002  00000000  00000002  RWIX
  INT13                 0000fffa   00000002  00000000  00000002  RWIX
  INT14                 0000fffc   00000002  00000000  00000002  RWIX
  RESET                 0000fffe   00000002  00000002  00000000  RWIX

Upvotes: 1

Views: 1738

Answers (1)

jeb
jeb

Reputation: 82390

It's unimportant how much RAM your system has, in your case the configured heap size is too small.

But if you always need 4 ringbuffers with a fixed size, it makes no sense to allocate them via malloc.
You could better define static variables, so you will know at link time if your RAM is enough.

#define RING_BUF_SIZE  32

typedef struct
{
    unsigned char Head;
    unsigned char Tail;
    unsigned char buffer[RING_BUF_SIZE];
} RingBuffer;

static RingBuffer myRingbuffer[4];

void RB_Init(RingBuffer *RB)
{
    memset(RB, 0, sizeof(RingBuffer) );
}

It's important to initialize them, as the code composer is not ANSI-C compliant here and the startup code will not zero all variables at startup.

Upvotes: 4

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