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Computer COM port & microcontroller COM port ??

Rutu Patil

Hi all,

I have written a program in VC++ to write a char array of 13 bytes on COM port using 9600-N-8-1 parameters.

when i send this to my target device it responds, but same program when i send through 89S51 my device does not respond.To set 9600-N-8-1 i have written 0xFD value.

Can anyone no the reason for such strange behaviour.

Please let me know....

rutu.

Parents
  • 0 in reply to Rutu Patil 

    #include<reg52.h>
#include<stdio.h>

char m_Write[13]={0x40,0x05,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x79,0xBF,0x0A};

char loop=13;

void main(void)
{
SCON=0x50;
TMOD |=0x20;
TH1=0xFD;
TR1=1;
TI=1;

while(1)
  {
  while(loop--)
    putchar(m_Write[13-loop]);
  loop=13;
  }
}

    The main problem I see is that the while loop you have only transmits 12 characters.

    At the beginning, you have set loop to 13. The while (loop--) decrements loop to 12. You then transmit m_Write[13-loop] and 13-12 is 1. However, the first array element is index 0. I would probably re-write the code as follows:

    #include<reg52.h>
#include<stdio.h>

static unsigned char m_Write[13] =
{0x40,0x05,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x79,0xBF,0x0A};

void main(void)
{
unsigned char loop;

SCON=0x50;
TMOD |=0x20;
TH1=0xFD;
TR1=1;
TI=1;

while(1)
  {
  for (loop = 13; loop; loop--)
    {
    putchar(m_Write[13-loop]);
    }
  }
}

    Jon

Reply
  • 0 in reply to Rutu Patil 

    #include<reg52.h>
#include<stdio.h>

char m_Write[13]={0x40,0x05,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x79,0xBF,0x0A};

char loop=13;

void main(void)
{
SCON=0x50;
TMOD |=0x20;
TH1=0xFD;
TR1=1;
TI=1;

while(1)
  {
  while(loop--)
    putchar(m_Write[13-loop]);
  loop=13;
  }
}

    The main problem I see is that the while loop you have only transmits 12 characters.

    At the beginning, you have set loop to 13. The while (loop--) decrements loop to 12. You then transmit m_Write[13-loop] and 13-12 is 1. However, the first array element is index 0. I would probably re-write the code as follows:

    #include<reg52.h>
#include<stdio.h>

static unsigned char m_Write[13] =
{0x40,0x05,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x79,0xBF,0x0A};

void main(void)
{
unsigned char loop;

SCON=0x50;
TMOD |=0x20;
TH1=0xFD;
TR1=1;
TI=1;

while(1)
  {
  for (loop = 13; loop; loop--)
    {
    putchar(m_Write[13-loop]);
    }
  }
}

    Jon

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