RE: [avr-libc-dev] Wishlist: place static bool in GPIO registers

[Stu Bell]

> The bit-field approach solves my primary complaint by not needing any 
> accessor functions. Both if (my_flag) and my_flag = true; work as 
> expected. As for the declaration, perhaps #define my_flag 
> (GPIOR0_BIT.bit0) would be sufficient, where GPIOR0_BIT is defined 
> by avr-libc as 
> 
> #define GPIOR0_BIT (*(volatile BitRegisterType
*)_SFR_MEM_ADDR(GPIOR0))

I think you need the pointer dereference (GPIOR0_BIT->bit0) instead of
the member dereference (GPIOR0_BIT.bit0).  Otherwise, what you suggest
is a pretty good idea.

Best regards, 

Stu Bell 
DataPlay (DPHI, Inc.) 


-----Original Message-----
From: Shaun Jackman [mailto:address@hidden 
Sent: Wednesday, December 19, 2007 2:26 PM
To: Stu Bell
Cc: Weddington, Eric; address@hidden
Subject: Re: [avr-libc-dev] Wishlist: place static bool in GPIO
registers

On Dec 19, 2007 1:24 PM, Stu Bell <address@hidden> wrote:
...
> The real problem with a full workup would be a macro to help define 
> "bit" variables.  For example it would be cool to do something like 
> the
> following:
>
> #define DECLARE_BIT_VARIABLE(var,port,bnum) \
>   #define (name)  ((volatile BitRegisterType*)_SFR_MEM_ADDR( (port ) 
> )->bit ## bnum
>
>
> The above code is completely wrong, as the preprocessor won't allow a 
> declare within a declare.  Does someone have a clue how to "nicely"
> declare a bit variable other than putting the above into a long 
> explanation in the comment header/documentation (which will surely be 
> ignored by the noobs)?
...

Cheers,
Shaun