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Pointer to struct

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E_Blue

Joined: 13 Apr 2011
Posts: 417

Pointer to struct

Posted: Mon Sep 12, 2011 9:48 am

I have the following function to write to an external SPI EEPROM.

Code:

void FillBufferEE(long StartAddress, char *DataBuffer, char ByteCount)
{
#warning "Esta funcion no controla desbordamientos de buffer; el buffer debe tener suficiente espacio para la cantidad de datos solicitados"
char x;
while(EE_Busy())
{
delay_us(10);
}
output_low(CS);
spi_write(Read);
spi_write(make8(StartAddress,1));
spi_write(make8(StartAddress,0));

for(x=0;x<ByteCount;x++)
{
DataBuffer[x]=spi_read(0);
}
output_high(CS);
}

And I think maybe I should declare it

Code:

void FillBufferEE(long StartAddress, char *DataBuffer[], char ByteCount)

I'm calling the function in many program points and is working OK but when I call the function and pass as a destination buffer a 32bit UInteger inside an struct did'nt work, It seems like doing nothing.

Code:

FillBufferEE(Timer1EE,Timer1.Setting,4);

_________________
Electric Blue

RF_Developer

Joined: 07 Feb 2011
Posts: 839

Re: Pointer to struct

Posted: Mon Sep 12, 2011 10:16 am

E_Blue wrote:

I have the following function to write to an external SPI EEPROM.

Code:

void FillBufferEE(long StartAddress, char *DataBuffer, char ByteCount)

Code:

FillBufferEE(Timer1EE,Timer1.Setting,4);

You need to pass the *address* of Timer1.Setting. You are passing its value, which will be interpreted as an pointer, with wrong results. You need the & operator:

Code:

FillBufferEE(Timer1EE,&Timer1.Setting,4);

If you wanted to fill an array you could write

Code:

FillBufferEE(Timer1EE,My_Array,4);

Code:

FillBufferEE(Timer1EE,&My_Array[0],4);

both should produce the same result. An array name without [] *is* a pointer in C. To pass a pointer to a specfic array element you need the & just as for a simple variable whether its in a struct or not.

RF Developer

E_Blue

Joined: 13 Apr 2011
Posts: 417

Pointer to struct
Posted: Mon Sep 12, 2011 12:04 pm

Thanks!, that works pretty well. _________________ Electric Blue

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