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problem with large buffers in ram

Salman Liaquat

Hi,
MCU: LPC2138
I am writing a code that takes data from serial port (interrupt driven) and stores it in queues.
Here's an overview:

//////////////
struct queue{
   char *buffer;
   int wp;
   in rp;
 };

char buffer1[6000];
char buffer2[1000];
char buffer3[600];
char uartBuffer[100];
struct queue myQueue;

void initQueue(char* bufferQueue, int size) {
    myQueue.buffer = bufferQueue;
    myQueue.wp = 0;
    myQueue.rp = 0;
}

void enqueue(char *data) {
  q = &myQueues;
  while(data[i] != '\0') {
        q->buffer[q->writePointer++] = data[i++];
        if (q->writePointer >= q->size)
                q->writePointer = 0;
        }
        q->buffer[q->writePointer++] = 0;
        if (q->writePointer >= q->size)
                q->writePointer = 0;
}

int main () {
  char str[50];
  UART0_init(9600);
  UART0_interrupt_init();
  initQueue(buffer3, 600);

  while(1) {
     sprintf(str, "wp: %d    rp: %d", myQueues.wp, myQueues.rp);
     UART0_sendstring(str);
  }
}

void UART0Isr() {
     UARTbuffer[i] = UART0_getbyte(); // get data until sequence completed
     if(/*sequence complete condition*/)
           enqueue(UARTbuffer);
}

Now, the problem is that the controller hangs after "enqueuing" 8 sequences(all sequences are same). and the number 8 decreases if i increase the size of sequence.

if i reduce the buffer3 size to 500 or less, code works perfectly fine.
for buffer3 size >= 500 ----> code hangs

if i interchange the declaration sequence of global variables like:

char buffer3[600];
char buffer1[6000];
char buffer2[1000];

it gets ok. Atleast for 1000 sequences.

if i disable all interrupts and use enqueue in main in a while loop, its runs fine.

void main() {
while(1) {
  enqueue(sequence);    //works fine here
}
}

Thanks for reading and advance thanks for helpful replies.

Regards,
Salman.

Parents
  • 0 in reply to Salman Liaquat

    Note that NXP recommendations can't take into account any Keil startup files that performs a memory copy of a vector table into RAM and how that copying could result in an overwrite of other information in case the application have stored something important to the overwritten address range.

    It's always important to understand what is happening in a system, which was the reason I did recommend you to first spend time with the processor user manual (to understand the functionality of the processor and the needs) before looking at the Keil startup file.

Reply
  • 0 in reply to Salman Liaquat

    Note that NXP recommendations can't take into account any Keil startup files that performs a memory copy of a vector table into RAM and how that copying could result in an overwrite of other information in case the application have stored something important to the overwritten address range.

    It's always important to understand what is happening in a system, which was the reason I did recommend you to first spend time with the processor user manual (to understand the functionality of the processor and the needs) before looking at the Keil startup file.

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