--- Andrew Warren <aiw@CYPRESS.COM> wrote:
>
> Anthony:
>
> A few things...
>
> 1.  #define isn't the correct way to declare your
> volume[][] array.
>

Got it.

> 2.  In C, array subscripts start at 0... So if
> you've declared an
>     array of size 2 (e.g., "int array[2];"), it
> contains elements
>     array[0] and array[1]; there's no array[2].
>

Right, I forgot about that.

> 3.  This is scary:
>
>         for (k = 7; k >= 0; k--)
>
>     If k is unsigned, it's by definition ALWAYS
> greater than or
>     equal to 0... The loop will never terminate.
>

I didn't define k anywhere, should this be done, or
will the compiler take care of that? I guess it's
better to put it explicitly in the code, right?

> 4.  An easier, faster, more code-efficient way to do
> your bit-
>     shifting is:
>
>         unsigned char k, temp;
>
>         ....
>
>         temp = volume[i][j];
>         for (k = 0b10000000; k != 0; k = k >> 1)
>         {
>             pga_latch = pga_latch & 0b11111110;
>
>             if (temp & k)
>             {
>                 pga_latch = pga_latch | 0b00000001;
>             }
>         }
>
>         ....
>
>     This puts the array lookup outside the loop so
> you only do it
>     once per byte, and it reduces the number of
> shifts per byte from
>     28 to 8.  It also gets rid of the "else" by
> always pulling SDI
>     low, then pulling it high when appropriate; it
> didn't look as
>     though that'd be a problem.

Thanks! I don't think pulling SDI low every time will
be a problem either, since it's set on the PGA2310
every rising edge of SCLK.

> 5.  Does your C compiler support bit-wide variables?
>  If so, it'd
>     make your code more readable and less
> error-prone, since you
>     could simply write "SDI = 0" or whatever,
> instead of the
>     complicated logical operations.  If not, "set"
> and "clear"
>     macros would do almost as well.

I had something like that first, but that seemed too
simple. I'm using the High-Tech PICC18 demo, but I
can't seem to get it to work. I might also try the
Microchip C18 compiler demo. I guess they support 1
bit wide vars?

Thanks, Anthony

=====
Website: http://members.lycos.nl/anthonyvh


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