Hi all,

Once again...back at my C project after a few weeks away. This time
I'm trying to streamline bit testing. I know there isn't a direct
equivalent to BTFSC in C, so I'm following some advice from the XC
manual, section 3.4.4.2 "How can I access individual bits of a
variable". It proposes creating a bit testing define like this:

#define  testbit(var, bit)  ((var) & (1 <<(bit)))

I am using this code in the following way:

      if(!(testbit(this_led, 23)))
      {          // test fixed bit 23
          SSP2BUF =3D ws2811_one;
      }
      else
      {
          SSP2BUF =3D ws2811_zero;
      }

What I am doing is testing the individual bits of a variable, then
using the result to decide what to send out via SPI (not relevant at
this point, but I am trying to control WS2812 LEDS). I am always
testing bit 23, then shifting the variable to the left to get at the
next value.

My issue is that my testbit always ends up returning 0. With the "!",
that means my code is always transmitting a 1. If I remove the "!", I
am always transmitting a 0.

My thought is that perhaps this is happening because of the bit I am
testing? The temp variable testbit is declared like this: "static
uint32_t this_led;", so it is actually a large enough variable to be
testing bit 23.

I had a look at the listing output of the compiler, and I found this:

852                           ;ws2812_lib.c: 37: if((((this_led) & (1 <<(23=
)))))
853  000548  A03E                   btfss    send_frame@this_led,0,c
854  00054A  D002                   goto    l1127

To me, it looks like the assembly code is testing bit 0. This would
make sense in that the assembly code doesn't natively support 32 bit
variables.

If my guesses are correct, what might be a better way to deal with
this? I would prefer to avoid testing bit 0 and shifting the other way
due to the order in which I need to send the bits.

Thoughts?

Thank you!

Josh
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