a problem in programming an avr with c

[m_pourfathi]

lbbl_endian_int

I don't understand what does these macros mean please help:

#define ETH_INT_ENABLE GICR |= (1<<INT2)

#define ENC28J60_CS_HI() ENC28J60_PORT |= (1<<ENC28J60_PIN_CS);

#define ENC28J60_REG_MAADR2 (0x63 | 0x80)

#define ENC28J60_TX_BUFFER_START ((unsigned int)0x1A00)

#define LO8(x) ((x)&0xFF)

#define LBBL_ENDIAN_INT(x) ((x & 0x00FF) << 8 ) + ((x & 0xFF00) >> 8 )

#define LBBL_ENDIAN_LONG(x) ((x & 0xFF000000) >> 24) + ((x & 0x00FF0000) >> 8 ) + ((x & 0x0000FF00) << 8 ) + ((x & 0x000000FF) << 24)

thanks

 

[pico]

avr c left shift

#define is a text pattern replacement directive.
from your example
#define LBBL_ENDIAN_INT(x) ((x & 0x00FF) << 8 ) + ((x & 0xFF00) >> 8 )

when compiling the complier will replace every
LBBL_ENDIAN_INT(x)
with
((x & 0x00FF) << 8 ) + ((x & 0xFF00) >> 8 )
before compiling
so after this #define you can write
LBBL_ENDIAN_INT(x) which easier to understand than
((x & 0x00FF) << 8 ) + ((x & 0xFF00) >> 8 )

 

[m_pourfathi]

lbbl_endian_long

I know, but what exactly is the meaning of the second part? I don't understand that part!

 

[funk_macole]

avr bitwise left shift c

Below is the assumption from me but for a better solution just type the complete line of the code where it is used.

actually here & is logical 'AND' operator which perfoms logical and operations on the two variables here it is x and 0x00FF or 0xFF00

And >>, << are bitwise operators which shifts the bits to the right or left in binary base, here it will do that 8 times, i.e. left shift 8 times and right shift by 8 times.

I think the statement is used to logical and the two variables, value of the x with
0x00FF and 0xFF00 then it performs the left shift and right shift 8 times whatever the value is.

Actually in binary each right shift devides the number by 2 and each left shift multiplies the number by 2.

 

[XNOX_Rambo]

LBBL_ENDIAN_INT(x) will transform an integer from little to big endian format - or vice versa.

If you don't know what that is, check here: https://en.wikipedia.org/wiki/Endianness

/Ram