How to convert long data to byte to write eeprom

[cllunlu]

Hi Everyone,

I read data from interrupt 1 or 0 and load a char array that length is 24. After that I converted that array to unsigned long value. Now I wanna write this data to eeprom with byte to byte.

Anyone help to me how to do converting byte to byte

Thank you

 

[KlausST]

Hi,

Why did you use the char (=byte) array to long?

Why not save the chars into the eeprom?

Klaus

 

[xenos]

...load a char array that length is 24. After that I converted that array to unsigned long value....

Reverse that procedure.
If you feel it's difficault to do that, then probably the initial procedure to convert byte array to unsigned long was neighter efficient, nor simple.
You could post this code here if you need help.
We do not even know what language you are programming in.

 

[cllunlu]

I use mikroC compiler. Assume that I have char array that size is 24 and values are {'1','0','1', ...}
I convert this array to long value (14811184). Now I have to write this data to eeprom. Now I can write it as three byte. Because size is 24 bit. How can I write this data to eeprom as 3 byte

 

[xenos]

typedef union {
           unsigned long l;
           unsigned char b[sizeof l];
} ul_bytes;

void do_something(unsigned long v){
     char i;
     ul_bytes u;
     u.l = v;
     for(i=0;i<3;i++){//assuming little endian
           write_eeprom(u.b[i]);
     }
}

or

//portable code
unsigned char i,x;
unsigned long l = 0x1234;
for(i=0;i<3;i++){
           x = (unsigned char)l;
           write_eeprom(x);
           l >>= 8;
}

or

//assuming little endian
#define GETBYTE(v,i)        (((unsigned char *)&v)[i])
      char i;

      //to write long to eeprom
      for(i=0;i<3;i++)
             write_eeprom(GETBYTE(v,i));

      //to read from eeprom into long
      for(i=0;i<3;i++)
             GETBYTE(v,i) = read_eeprom();
}

I use mikroC compiler. Assume that I have char array that size is 24 and values are {'1','0','1', ...}
I convert this array to long value (14811184). Now I have to write this data to eeprom. Now I can write it as three byte. Because size is 24 bit. How can I write this data to eeprom as 3 byte

 

[KlausST]

Hi,

Why not bit shift the incoming data in a 3 byte array?

I don't see the benefit of using 24 bytes using only a single bit each...


Klaus

 

[cllunlu]

I couldnt understand that code

Especially x = (unsigned char)l;

//portable code
unsigned char i,x;
unsigned long l = 0x1234;
for(i=0;i<3;i++){
           x = (unsigned char)l;
           write_eeprom(x);
           l >>= 8;
}

- - - Updated - - -

I wanna read wiegand26 data. Device sends 24+2 bit to me. I wanna record this data to eeprom

 

[betwixt]

The '(unsigned char)' is tells the compiler that the number flowing it is to be treated as though it is an unsigned character value rather than it's original size. In this instance it makes it ignore the first 16 bits and only use the last 8. Later in the loop, the 24 bit value is shifted 8 positions to the right which means what was originally bits 15:8 are then in positions 7:0 where they can then be treated as an unsigned char again.

Brian.

 

[horace1]

so long the write_eeprom() function prototype was declared as

write_eeprom(unsigned char x);

the long would be truncated to unsigned char when the function is called

 

[xenos]

so long the write_eeprom() function prototype was declared as

write_eeprom(unsigned char x);

the long would be truncated to unsigned char when the function is called

with an annoying warning produced by the compiler...

 

[FvM]

the long would be truncated to unsigned char when the function is called

Are you talking about the code in post #5? Nothing is truncated therein.

 

[cllunlu]

When I write and read eeprom data, have some problems. I am trying to write eeprom. After that I check it programmer software that is ok. But When I read data that address, it doesnt send truth data.

unsigned short addr;
unsigned char deneme[2];

EEPROM_Write(0x10,'C'); // Write some data at address 2
EEPROM_Write(0x11,'E');
EEPROM_Write(0x12,'L');
EEPROM_Write(0x13,'A');
EEPROM_Write(0x14,'L');

addr= EEPROM_Read(0x13);
shortToStr(addr,deneme);
UART1_Write_Text(deneme);

 

[xenos]

When I write and read eeprom data,...

// Write some data at address 2???
Do you know that 0x10 is equal to 16 and 0b10 is equal to 2?

Try this

    unsigned char deneme[2];
    deneme[1] = 0;

    EEPROM_Write(0x10,'C');
    EEPROM_Write(0x11,'E');
    EEPROM_Write(0x12,'L');
    EEPROM_Write(0x13,'A');
    EEPROM_Write(0x14,'L');
    
    deneme[0] = EEPROM_Read(0x13);
    UART1_Write_Text(deneme);

you should read 'A' in the rs232 terminal

ps. I do not know the prototypes of EEPROM_Write and shortToString, I assume what they do by their names

- - - Updated - - -

Are you talking about the code in post #5? Nothing is truncated therein.

I assume that he talks about omiting the type casting of [unsigned long] to [unsigned char], because it will be automaticaly done by the compiler (if the definition of function...).
This is why I replied:

with an annoying warning produced by the compiler...

 

[FvM]

I assume that he talks about omiting the type casting of [unsigned long] to [unsigned char], because it will be automaticaly done by the compiler (if the definition of function...).

O.K., so it's a suggestion to omit the superfluous x variable. You can in fact do this without generating a warning by pulling the type cast into the function call.