18.4 unions shall not be used - Printable Version

Code:
Example_Ports.h /* eg. a processor library of a processor manufacturer */

-----------FILE START----------------

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#define PORTA        (*((volatile uint8_t *)(2000)))

/* So with \"PORTA\" we get access to data content of PORTA (adress 2000), it is a unsigned char, 8 bits. The file and this line is given by the processor manufacturer */

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-----------FILE END----------------











/*Example_Test.c /* the example c file*/

-----------FILE START----------------

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typedef union {

  uint8_t cb ;

  struct bits {

    uint8_t

    b0 : 1,

    b1 : 1,

    b2 : 1,

    b3 : 1,

    b4 : 1,

    b5 : 1,

    b6 : 1,

    b7 : 1 ;

 } b ;

}example_bitfield;





#define B7       b.b7

#define B6       b.b6

#define B5       b.b5

#define B4       b.b4

#define B3       b.b3

#define B2       b.b2

#define B1       b.b1

#define B0       b.b0





    #define bitf_porta  (*((volatile example_bitfield*) &PORTA))

    /* Typcast to easy and safty access to each bit, see next line */





    #define porta_light bitf_porta.B5

    /* for a good identifier for the bit. which is for example for a light */





int main(void)

{

    uint8_t x;

    x = 0;



/* Now we can easy use the bits of the ports of the processor manufacturer. eg: */



        porta_light = 1;

        x = porta_light;



}