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Struct?

 
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lam
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Struct?
PostPosted: Sun Jan 24, 2010 5:36 am     Reply with quote
Have question about Struct.

Lets say I've got:
Code:

struct {
int16 a;
int8 b;
int8 c;
int16 d;
};

I want to transfer it via SPI.

Is there any method to make it automatically ? (in 'for (;;) or while loop'?)

Or do I need to do it manual like
spi_write(struct.b); spi_write(struct.c) etc.
Torello



Joined: 29 Sep 2006
Posts: 111

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PostPosted: Sun Jan 24, 2010 7:50 am     Reply with quote
Hi,

Below a solution. You need to setup the Spi-bus first. The function typecasts the struct as pointer to a byte array. Therefore you also need to pass along the size of this array. The sizeof takes care of this.

Be aware: int16 are put in memory as Lsbyte-Msbyte, so that is also the order that this function will put out int16.


Code:



// --- Typedef the struct
Typedef struct{   
struct {
int16 a;
int8 b;
int8 c;
int16 d;} IamStructType;

//--- Declare the struct variable
IamStructType  Iam;


//--- call the function somewhere in your program
spi_writeStruct(&Iam, sizeof(Iam));


// === function ====================================
void spi_WriteStruct(int8 *src, int8 szf) {
// usage: spi_WriteStruct( (int8*)&Struct, sizeof(Struct) )
   int8 wbyte;
   int8 idx;
   for(idx=1; idx < szf; idx++) {                         
      wbyte = src[idx];                                    //get the byte out the structure         
      spi_write(wbyte);                                    //spi write the byte

   }   
}
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