On reconfiguring GPIO with TMS320F28035PN

Hi.

I am trying to create registers with just certain GPIO bits.

To do that I changed the DSP2803x_Gpio.h file. Here's an example that is working on my code:

struct GPADATDAC_BITS {
   Uint16 GPIO7:1;           // 0      GPIO7
   Uint16 GPIO8:1;           // 1      GPIO8
   Uint16 GPIO9:1;           // 2      GPIO9
   Uint16 GPIO12:1;          // 3      GPIO12
   Uint16 rsvd1:12;            // 15:12  reserved
};

union GPADATDAC_REG {
	Uint16                  all;
	struct   GPADATDAC_BITS bit;
};

I then add the following line to GPIO_DATA_REGS: 

union  GPADATDAC_REG    GPADAC;

This works perfectly well. I can set those bits as outputs, and I can see the output changing. However if instead of using some of the lower 16 bits I use some of the upper 16 bits of GPA, I can't ever see the output changing.

The change I make to the code above is:

struct GPADATDAC_BITS {
   Uint16 GPIO16:1;          // 4      GPIO16
   Uint16 GPIO17:1;          // 5      GPIO17
   Uint16 GPIO18:1;          // 6      GPIO18
   Uint16 GPIO25:1;          // 7      GPIO25
   Uint16 GPIO26:1;          // 8      GPIO26
   Uint16 GPIO27:1;          // 9      GPIO27
   Uint16 GPIO30:1;          // 10     GPIO30
   Uint16 GPIO31:1;          // 11     GPIO31
   Uint16 rsvd1:8;            // 15:12  reserved
};

In this case nothing works. I can't see the outputs changing. 

Note I did not include the code that sets the bits as outputs (by changing GPAMUX1/2 and GPADIR). I've tested those in hardware by using the original library and they work fine there...

Thanks in advance.