c programming help,preprocessor

[dizgah]

hi every body
what does this code do ?

#define k1 [B]((uint16_t)0x0000)[/B]

im familiar with duty of define preprocessor instruction,but i dont know what does bold section do.
tnks

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my second question is:

void SPI_Init(SPI_TypeDef* SPIx, SPI_InitTypeDef* SPI_InitStruct)

in above function why we declare input variable in this method ,and dont declare usual like:

voide m1(int1,int2);

tnks again

 

[amnandu]

#define creates as macro.

In the line mentioned
#define k1 ((uint16_t)0x0000)

A simple k1 can be used in a code when ever ((uint16_t)0x0000) is used.

Using this identifier the code can be made readable.

I would prefer to you something more readable Identifier than k1.

 

[dizgah]

tnks i know, k1 was only for example
as i said i know function of define preprocessor ,my ques is what does

((uint16_t)0x0000)

do ?
as i know that say declare k1 equal with 0x0000 and 0x0000 is a 2byte size variable(unsigned int ),am i true?
then why we dont write

 #define k1 0x0000

cant compiler know size of constant/var from number of digits?
and we say it to compiler with this method ?
--------------
whats my second ques answer ?
tnks

 

[amnandu]

((uint16_t)0x0000)

With the above line you mention that it is a 16 bit value i.e 2Bytes.

You are typecasting the value to a 16bit where you have only assigned 4bits. Remaining bits are set to zero by type casting as above.

For second question :

There is a called function and calling function.
Called function : When one piece of code invokes or calls a function.
Example voide m1(int1,int2);
Calling funciton : When called by a function, this piece of code tells what needs to be done.
Example void SPI_Init(SPI_TypeDef* SPIx, SPI_InitTypeDef* SPI_InitStruct)

In the above calling function, SPI_TypeDef and SPI_InitTypeDef are defined in the code as structures. SPIx and SPI_InitStruct are initialised to create a temp value

SPIx. a = 123; SPIx.b = 456; ... etc.

In called function.. int1 and int2 initialized in main and are have a scope of using those variables in whole program. These two examples are not the perfect way to look at the called and calling function.

Hope am being clear .....

 

[milan.rajik]

In

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Code C - [expand]
1
SPI_Init(SPI_TypeDef* SPIx, SPI_InitTypeDef* SPI_InitStruct)

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SPI_TypeDef* is a pointer to SPI_TypeDef type and SPI_InitTypeDef* is a pointer to SPI_InitTypeDef type.

SPIx and SPI_InitStruct are other two types of data types. They are defined else where in the code.

You have to post the full code for better answer.