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Is this code for page read write to 24LC512 EEPROM correct ?

 
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arunb



Joined: 08 Sep 2003
Posts: 492
Location: India

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Is this code for page read write to 24LC512 EEPROM correct ?
PostPosted: Mon Nov 11, 2013 8:59 am     Reply with quote
Hi,

I am trying to develop page read and write functions for the 24LC512 EEPROM. The EEPROM is i2c based.

My code is given below.

Code:

devaddress=0xA0;
int nMMCBuffer[512];

//reads 512 bytes from the EERPROM
void pageread_ext_eeprom(int devaddrs,long int address){

   int16 bytecntr;
       
        //device address
   bit_clear(devaddrs,0);

   i2c_start();
   i2c_write(devaddrs);
   i2c_write(address>>8);
   i2c_write(address);
   i2c_start();

   //read mode
   bit_set(devaddrs,0);
   i2c_write(devaddrs);

   //read in the data
   bytecntr=0;
   for (bytecntr=0;bytecntr<=511;bytecntr++){   
      nMMCBuffer[bytecntr]=i2c_read(1);
      bytecntr++;
   }

   //no acknowledge, stops transfer
   i2c_read(0);
   i2c_stop();

}

//writes 512 bytes of data to the eeprom
void pagewrite_ext_eeprom(int devaddrs,long int address){

   int16 bytecntr;
   int pgcnt,i;
   short int status;
   
   bit_clear(devaddrs,0);

   i2c_start();
   i2c_write(devaddrs);
   i2c_write(address>>8);
   i2c_write(address);

   bytecntr=0;

   for (pgcnt=0;pgcnt<4;pgcnt++){
      //transfer 128 bytes to on-chip page buffer
      for (i=0;i<=127;i++){   
         i2c_write(nMMCBuffer[bytecntr]);
         bytecntr++;
      }
   
      //transfers data from page buffer to EEPROM (actual write)
      i2c_stop();

      //poll for status of write
      i2c_start();
      status=i2c_write(devaddrs);
      while(status==1)
      {
         i2c_start();
         status=i2c_write(devaddrs);
      }

   }

   i2c_stop();

}



I just want an opinion, I have not tried this yet I will do so tomorrow.

thanks
a
Ttelmah



Joined: 11 Mar 2010
Posts: 19538

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PostPosted: Mon Nov 11, 2013 10:21 am     Reply with quote
Several little comments.

Your read code, physically sets the low bit of devaddress. Means it won't work a second time, nor will the write, since the address is now set to 'read'...

Better to use:
Code:

#define READ 1

//Then to select read mode:

   //read mode
   i2c_write(devaddrs | READ);


This way the physical address is never changed.

Then you'll have a problem if the ROM address given to the functions, is not the start of a page.... Need to test for this.

I'd suggest you don't do the extra read to stop the transaction, but instead include this in the read:
Code:

   //read in the data
   for (bytecntr=0;bytecntr<=510;){   
      nMMCBuffer[bytecntr++]=i2c_read(1);
   }

   //no acknowledge, stops transfer
   nMMCBuffer[bytecntr]= i2c_read(0); //last read stops the transfer
   i2c_stop();


You are incrementing the counter twice in the loop, and clearing it twice before starting....

Best Wishes
arunb



Joined: 08 Sep 2003
Posts: 492
Location: India

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RE:
PostPosted: Mon Nov 11, 2013 11:40 am     Reply with quote
Thanks, I didn't see those errors...

The ROM address is addressed like this.

address=512*Index

Index =0,1,2...n

so address will be= 0, 512, 1024 etc...

Do you think this will avoid the page boundaries...??

thanks
a
Ttelmah



Joined: 11 Mar 2010
Posts: 19538

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PostPosted: Mon Nov 11, 2013 2:34 pm     Reply with quote
Looks good.

Why not make the functions just take the index then?.

Best Wishes
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