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Problem using "strncmp"

 
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pilar



Joined: 30 Jan 2008
Posts: 197

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Problem using "strncmp"
PostPosted: Thu Jul 13, 2017 8:59 am     Reply with quote
Hi

Hello, I'm trying to compare two char strings using "strncmp", but I can not get it to work properly. Someone could tell me what is my mistake..

Here is my code:

Code:
#include <18F4520.h>
#device PASS_STRINGS=IN_RAM
#fuses HS,NOWDT,NOPROTECT,NOLVP,NOBROWNOUT,NOSTVREN
#use delay(clock=20MHz)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)// RS232 Estándar

#include <stdlib.h>

#define LED             PIN_D0
#define ON                 output_high
#define OFF                output_low

int const maxLongBuffRX=42;       
char bufferRX[maxLongBuffRX];       
int indBufferRX=0x00;          
char XCommand[maxLongBuffRX];    
char flag_RptaCommand;
int i;

void Add_bufferRX(char c);
void SendATCommand( char *pCommandTX );

#int_rda
void serial_isr() {
  if(kbhit()){
    Add_bufferRX(getc());
  }
   flag_RptaCommand = 1;
}

void Ini_buff_rec(void){
  int i;
  for(i=0;i<maxLongBuffRX;i++){
    bufferRX[i]=0x00;
  }
  indBufferRX=0x00;
}

void Add_bufferRX(char c){
  switch(c){
    case 0x0D:
      break;
    case 0x0A:
      break;
    default:
      bufferRX[indBufferRX++]=c;
  }
}

void SendATCommand( char *pCommandTX, char *pRXCommand ){
char *ptr;

   Ini_buff_rec();
   flag_RptaCommand = 0;

   printf ("%s",pCommandTX);
   putc('\r');
   
   while (   flag_RptaCommand == 0);

   //ptr=strstr(bufferRX,pRXCommand);

   if(strncmp(bufferRX,pRXCommand,strlen(pRXCommand))== 0)
      ON (LED);
   else
      OFF (LED);
}

void main(){

   OFF(LED);
   enable_interrupts(INT_RDA);
   clear_interrupt(INT_RDA);
   enable_interrupts(GLOBAL);

    SendATCommand("AT", "OK");

   delay_ms(200);

while (TRUE);
}
Ttelmah



Joined: 11 Mar 2010
Posts: 19259

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PostPosted: Thu Jul 13, 2017 9:09 am     Reply with quote
There is a basic problem that you don't really want to do the test until you have the entire reply.

Change your interrupt handler:
Code:

#int_rda
void serial_isr() {
  if(kbhit()){
    Add_bufferRX(getc());
  }
}

void Add_bufferRX(char c){
  switch(c){
    case 0x0D:
      bufferRX[indBufferRX++]='\0';
      flag_RptaCommand = TRUE;
      break;
    case 0x0A:
      bufferRX[indBufferRX++]='\0';
      flag_RptaCommand = TRUE;
      break;
    default:
      bufferRX[indBufferRX++]=c;
  }
}


This way the flag to say a command has been received, will only be set when the carriage return after the 'OK' is seen, not after just one character. You also then have a proper null terminated string, which currently you don't have.
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