rfreader

There are several errors. But don't you find them when you test your code? You are realizing the existence of a debugger?

1) Your ISR don't do anything in case the input buffer already is filled.
2) You let the ISR pick up 12 characters. Are you sure the 12th character of input[] would match the 12th character of your reference keys?
3) How do you get your ISR to synchronize the input, in case you miss one character or there is one character too much? Consider what happens if you disconnect/reconnect the serial cable while data is transmitting? Wouldn't it be good to consider '$' or '\r' or '\n' as synchronization characters?
4) Why do you send back null characters?

SBUF=0;

Or do you happen to believe that writing 0 to SBUF is clearing the just received character?
5) Do you really think it's safe to ignore the input_done check in main()? How fast can the ISR find 12 characters? How fast can main() start calling memcmp()?
6) Haven't we already discussed the bad idea of having the program run out of main()?
7) Do you happen to think that the 8051 processor works best when it has 16-bit integers to operate on - or you think it needs the "int" data type to fit the values 0 and 1 (or the input position)?

int  input_done = 0;       /* 0 = not done yet, 1 = all input read */

There are several errors. But don't you find them when you test your code? You are realizing the existence of a debugger?

1) Your ISR don't do anything in case the input buffer already is filled.
2) You let the ISR pick up 12 characters. Are you sure the 12th character of input[] would match the 12th character of your reference keys?
3) How do you get your ISR to synchronize the input, in case you miss one character or there is one character too much? Consider what happens if you disconnect/reconnect the serial cable while data is transmitting? Wouldn't it be good to consider '$' or '\r' or '\n' as synchronization characters?
4) Why do you send back null characters?

SBUF=0;

Or do you happen to believe that writing 0 to SBUF is clearing the just received character?
5) Do you really think it's safe to ignore the input_done check in main()? How fast can the ISR find 12 characters? How fast can main() start calling memcmp()?
6) Haven't we already discussed the bad idea of having the program run out of main()?
7) Do you happen to think that the 8051 processor works best when it has 16-bit integers to operate on - or you think it needs the "int" data type to fit the values 0 and 1 (or the input position)?

int  input_done = 0;       /* 0 = not done yet, 1 = all input read */

There are several errors. But don't you find them when you test your code? You are realizing the existence of a debugger?

1) Your ISR don't do anything in case the input buffer already is filled.
2) You let the ISR pick up 12 characters. Are you sure the 12th character of input[] would match the 12th character of your reference keys?
3) How do you get your ISR to synchronize the input, in case you miss one character or there is one character too much? Consider what happens if you disconnect/reconnect the serial cable while data is transmitting? Wouldn't it be good to consider the dollar or '\r' or '\n' as synchronization characters?
4) Why do you send back null characters?

SBUF=0;

Or do you happen to believe that writing 0 to SBUF is clearing the just received character?
5) Do you really think it's safe to ignore the input_done check in main()? How fast can the ISR find 12 characters? How fast can main() start calling memcmp()?
6) Haven't we already discussed the bad idea of having the program run out of main()?
7) Do you happen to think that the 8051 processor works best when it has 16-bit integers to operate on - or you think it needs the "int" data type to fit the values 0 and 1 (or the input position)?

int  input_done = 0;       /* 0 = not done yet, 1 = all input read */

#include<reg51.h>
#include "_LCD_R8C.c"

#define INPUT_LENGTH 11
char input[INPUT_LENGTH];  /* The input from the serial port */
int  input_pos  = 0;       /* Current position to write in the input buffer */
char getCharacter (void);        /* read a character from the serial port */

int main()
{
int i;

lcd_init();
lcd_clear();
SCON = 0x50;
TMOD = 0x20;
TH1  = 0xFD;
TR1  = 1;
TI   = 1;
RI   = 1;

while(1==1)
        {

               /* read the next character from the serial port */
                        input[input_pos++] = getCharacter ();

                        for(i=0;i<=input_pos;i++)
                        {
                            lcd_print_b(input[i]);
                        }
        }
}
char getCharacter (void)
{
      char chr[INPUT_LENGTH];           /* variable to hold the new character */
        while (RI != 1) {;}
        chr[input_pos++] = SBUF;
        RI = 0;
        return(chr);
}

first I tried displaying on the hyper terminal. I am getting correct value on the hyper terminal then I tried displaying the received number on the display, but I am getting the wrong value 002100 instead of $0016221826..

The trial-and-error continues.

Why have a getCharacter() function that has a local array chr[INPUT_LENGTH]? What do you think this one is used for? You receive one (1) character. You place it at a specific index in chr[].

Then you do something very interesting. You take the address of the array chr[] (yes, the name of an array represents a pointer to the first element in the array) and decides to convert this address into a character to be returned.

Haven't you got that C programming book yet? It would have told you a lot about how to use arrays. It would even have told you that the getCharacter() function have zero reason to contain an array since it is only intended to pick up one (1) character from the serial port and then return that single character.

Another thing - I have multiple times asked: Why do you print multiple characters to the LCD whenever you receive one more character? Don't you find it confusing to try to understand the printout on the LCD? Because I see no code that clears the LCD and start each loop by printing from the start of the line.

So if you receive the caracters 12345 on the serial port, your code would like to print 112123123412345 on the LCD - how helpful is that?

Or in reality - your LCD prints doesn't even print that. Because you print 2 characters when you have received 1. You print 3 characters when you have received 2. So the last character printed is always some data remaining since the previous iteration of your loop.

Yet another thing - you have an array with room for 11 characters. And an infinite loop repeating getCharacter() and then printing. What happens when you receive the 12th, 13th or 100th character? Where does it get saved?

Don't you think that a C text book and some quality time with a debugger would give better progress? Thowing LEGO pieces up in the air and check where they randomly land isn't likely to produce a nice castle or space ship. Right now, you are cutting/pasting/moving around source code without actually trying to understand what is actually happening. You can continue for 10 years without getting a working program, because it really is quite hard to throw 50 dices and get all 50 to show the value "6" at the same time. With better methodology, you could throw the first dice until it shows a "6". Then take the second dice and throw until you get a "6". Then the third. Then the fourth. That would give progress. The information from a C text book could give progress. The use of a debugger could give progress. Random code changes are likely to break as much as improving. So the probability of progress is very low. That is the reason why the days are ticking, while your school buddies have probably already managed to get their implementations to work by now.

Shortcuts can be very good when you know where they lead. Random shortcuts are known to lose time or get people completely lost.

ya your right, but what to do, I need to submit this program as fast as possible. . only 2 days remaining. I have studied the comparing of arrays and that part is completed. The only problem is in receiving char using interrupt and displaying it.

Now I have corrected all the mistakes still it is displaying 255 on the display.

once i am able to receive the char then I will finish off this program and take a break to study.

even I am feeling very bad.

Now I have corrected all the mistakes still it is displaying 255 on the display.
HUH? if it is "displaying 255 on the display" it is not possible that you have "corrected all the mistakes"

once i am able to receive the char then I will finish off this program and take a break to study
AKA sequencing error

while(1==1)
        {

               /* read the next character from the serial port */
                        input[input_pos++] = getCharacter ();

                        for(i=0;i<=input_pos;i++)
                        {
                            lcd_print_b(input[i]);
                        }
        }
}
char getCharacter (void)
{
      char chr[INPUT_LENGTH];           /* variable to hold the new character */
        while (RI != 1) {;}
        chr[input_pos++] = SBUF;
        RI = 0;
        return(chr);
}

since the above read and display characters one by one why are you using arrays?
what happens if you do this

lcd_print_b ('U');

you are making the mistake of writing code instead of growing code. get one thing to work at a time.

Erik

ya i am getting the same display like 112122123. . please help me to complete the program

lcd_print_b ('U');.. I am not getting.. please explain in detail.

#include <reg51.h>
#include "_LCD_R8C.c"

#define INPUT_LENGTH 11


int main()
{
  char input[INPUT_LENGTH];  /* The input from the serial port */
  int  input_pos  = 0;       /* Current position to write in the input buffer */

  lcd_init();
  lcd_clear();

  SCON = 0x50;
  TMOD = 0x20;                /* timer 1, mode 2, 8-bit reload */
  TH1  = 0xFD;                /* reload value for 2400 baud */
  TR1  = 1;
  TI   = 1;
  RI   = 1;

  while(1)
  {
    /* read the next character from the serial port */
    if(input_pos < INPUT_LENGTH)    /* check for buffer overflow */
    {
      input[input_pos] = getCharacter();
      lcd_print_b(input[input_post]);  /* only makes sense to print each character once */
      input_pos++;
    }
 }


 char getCharacter (void)
 {
   char chr          /* variable to hold the new character */

   while (RI != 1)
     ;

   chr = SBUF;
   RI = 0;

   return(chr);
 }

i am getting display as 255... help me out...

Why are you not cutting/pasting your code?

The last code you posted is not your real code - check the spelling of your index when printing - what is "input_post"???

And how come you #include a c file? Why would there be both *.h and *.c files if it was intended that you should include *.c files?

ok sorry i ll correct it... i have got few questions
1) is it receiving all the characters ?
or it is receiving all characters and me not able do display it on lcd?..

"is it receiving all the characters? or it is receiving all characters and me not able do display it on lcd?"

That really is something for you to determine in your own debugging of your system!

you presist in throwing the whole thing together and asking "what is wrong"

DIVIDE AND CONQUER!

Erik

#include <reg51.h>
#include <string.h>
#include "lcd.h"

#define INPUT_LENGTH 12
#define ACCEPTABLE_INPUT_COUNT 2
char getCharacter(void);
int  input_pos=0;
char input[INPUT_LENGTH];
int main()

{
        int i,j;
        /* Array of data that this programs thinks is acceptable */
        char acceptable_inputs[ACCEPTABLE_INPUT_COUNT][INPUT_LENGTH] = {
        "$0016221826", "$0016234114"};
          lcd_init();

          lcd_clear();

          SCON = 0x50;

          TMOD = 0x20;                /* timer 1, mode 2, 8-bit reload */

          TH1  = 0xFD;                /* reload value for 2400 baud */

          TR1  = 1;

  while(1)
  {
        input[input_pos++] = getCharacter();
        if(input_pos==11)
        {
                 for (i = 0; i < ACCEPTABLE_INPUT_COUNT; i++)
                {
                j = strcmp(acceptable_inputs[i],input);
                 if(j==0)
                         {
                        lcd_printxy(1,8,"yes");
                        input_pos=0;
                                }
                                else
                                {
                                lcd_printxy(1,1,"no");
                                input_pos=0;
                                }
                  }
                  }
   }
}

 char getCharacter (void)
 {

    char chr;          /* variable to hold the new character */
    while (RI != 1)
     ;
    chr = SBUF;
    RI = 0;
   return(chr);
 }

when i debug step wise its working properly. when i download it to the microcontroller and give input i.e rfreader will read the ID number and sends it to MCU, the o/p is no, and again when i try to download for the next time i,e as soon as i click on "start" to download the program, output will be yes. Please help me to resolve this

Sorry, but no. You haven't debugged your code. It does not work when you step through it either.

You don't need to step through in a debugger - enough to follow the flow with pen and paper and try three different alternatives.
Code matching first acceptable key.
Code matching second acceptable key.
Code not matching any key.

for (i = 0; i < ACCEPTABLE_INPUT_COUNT; i++) {
    j = strcmp(acceptable_inputs[i],input);
    if (j==0) {
        lcd_printxy(1,8,"yes");
        input_pos=0;
    } else {
        lcd_printxy(1,1,"no");
        input_pos=0;
    }
}

How did you decide that if your input fails the test against the first code, it's a failure? Don't you think you need to iterate through the full array and first when all known codes mismatches, it's a fail?

Did't you notice that when you did your stepping through the code?

Why are you in such a hurry? The logic is simple. But to get something to work, you need to have the patience to work out all acceptable and unacceptable paths and verify that they they happen as expected. Any time you take a shortcut, you cut yourself. It is costing _you_ a lot of time, that you don't work a bit slower and really try to follow the logic of your code.

for (i = 0; i < ACCEPTABLE_INPUT_COUNT; i++) {
    j = strcmp(acceptable_inputs[i],input);
       if(j==0)
       break;
     }
    if (j==0) {
        lcd_printxy(1,8,"yes");
        input_pos=0;
    } else {
        lcd_printxy(1,1,"no");
        input_pos=0;
    }

as you said i am getting problem in this part of code. it is receiving all the characters but not able to compare, it is printing "no" on the lcd.. i am not able find out why it is happening so, Sir please help me out. which step of the above code should be corrected.

@Andrew Neil

Why don't you write a bit of the code at a time and test it before doing the next bit. You stand a chance of creating a whole project that works properly.