Re: [avr-gcc-list] Using flash memory for storing large look up tables

[Royce Pereira]

Hi,

Whew!

Have you read the avr-libc manual & the FAQ therein? Please read up the useful 
macros provided for program memory store & access!

If you would have, you would have tried this: (The [2][4] are for example):
//----------------
unsigned todayssunset;

const unsigned sunrise[2][4] PROGMEM ={         1,2,3,4,        6,7,8,9  };

todayssunset= pgm_read_byte(&sunrise[x][y]);
//-----------------
All this and more is covered in the AVR libc manual & FAQ.

--Royce.

On Tue, 24 Jan 2006 12:46:08 +0530, dhananjay deshpande <address@hidden> wrote:

> Hi,
>   I am learning to use AVRGCC. I am using it in AVRSTUDIO.
>   I have a difficulty for my application of "sunset switch on- sunrise switch off 
> relay", which requires a look up table of ~730 integers to be stored in the program. 
> I do not have any other option but to save this table in program memory.
>   I am using ATMEGA 8535L, I am using assynchronous timer and external 32kHz 
> crystal for realtime keeping.
>   Question is how to store and retrieve the table contents.
>   I started with a little short table of 2 months timing for sunset and sunrise.
>   the code was as follows
>   for storing the sunset and sunrise timings
>   const int __attribute__((section(".text"))) sunrise[2][31]={
>                            {601,602,603,604,605,606,607,608,609,610,
>                             611,612,613,614,615,616,617,618,619,620,
>        621,622,623,624,625,626,627,628,629,630,631}
>        ,{                                         }
>            };
> const int __attribute__((section(".text"))) sunset[2][31]= {
>                             {1801,1802,1803,1804,1805,1806,1807,1808,1809,1810,
>         1811,1812,1813,1814,1815,1816,1817,1818,1819,1820,
>         1821,1822,1823,1824,1825,1826,1827,1828,1829,1830,1831}
>          {          }                  };
>  for retrieving
>  todayssunset=sunset[t.month][t.date] ;  //t is a structure .
>  This retrieving doesnot work if I use __attribute__((section(".text"))).
>  If I do not use section(".text") attribute, the table is stored in data space 
> which is insufficient . Is there any way out?  please help.
>   Thanks in advance
>  avr_learner
>
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