Re: Saving & retreiving a structure in eeprom

[Dave Hansen]

You wrote

>>>   eeprom_read_block((void *)&setPgm, (const void *)eepLoc, num) ;

What is num?

   -=Dave

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From: AVR-GCC-list <avr-gcc-list-bounces+iddw=hotmail.com@nongnu.org> on behalf of Royce Pereira <roycejp@gmail.com>
Sent: Tuesday, June 9, 2020 8:18 AM
To: avr-gcc-list@nongnu.org <avr-gcc-list@nongnu.org>
Subject: Saving & retreiving a structure in eeprom

 

Hi,

The MPU is ATMega8. AVR-GCC version is 9.1.0

I have a structure that I'm trying to save (& retrieve in eeprom).

Furthermore, it is to be saved in an indexed location in the eeprom from 0 to 29.

The structure is 4 bytes in size. So total 127 bytes are used in EEPROM

//-----------------------------------------

#define EEP_START    7     //offset in EEPROM where my structure storage starts.

typedef struct

{

   int  temp ;

   unsigned int time ;

} _pgm ;

#define STRU_SIZE    (sizeof(_pgm))

_pgm       setPgm ;       //create struct in RAM.

uint16_t    eepLoc ;   //holds address of EEPROM

uint8_t      index ;      //index to read from in EEPROM...

//----------------------------------------------------------

//save struct from RAM to an indexed location in EEPROM...

void savPgm(char idx)

{

    eepLoc = EEP_START + ((uint16_t)idx * STRU_SIZE) ;  

    eeprom_write_block((const void *)&setPgm, (void *)eepLoc, STRU_SIZE) ;

   return ;

}

//-------------------------------------------------------

//Retreive struct from an indexed location in EEPROM....

void getPgm(char idx)

{

   eepLoc = EEP_START + ((uint16_t)idx * STRU_SIZE) ;  

   eeprom_read_block((void *)&setPgm, (const void *)eepLoc, num) ;

  return ;

}

//------------------------------------------

int main(void)

{

index = 5 ;

setPgm.temp = 50 ;

setPgm.time = 10 ;

savPgm(index) ;    //example  .. save in 6th location in EEPROM;

//Now read the saved struct back from eeprom...

// this reads back correctly.:-

setPgm.temp = eeprom_read_word((const uint16_t *)eepLoc) ; //eepLoc was set before.

setPgm.time = eeprom_read_word((const uint16_t *)eepLoc + 1) ;

//But this reads 0xFFFF for both elementss. (Why?):-

getPgm(index) ;  //uses block-read function

return 0 ;

}

//---------------------------------------------------------------

The getPgm function uses the read block api but retreives garbage(0xFFFF);

What am I doing wrong ?

Thank you!

--

Best Regards,

-- Royce Pereira

--

Best Regards,

-- Royce Pereira