Using IO

[AtomSoft]

Ok this is too much... i never would have guessed XMOS to mess up (in my mind) with their IO stuff..

Ok i know how to set a port to in or out...ex...

out port LEDS = XS1_PORT_8A;

I also know how to set each bit ...

LEDS <: SOMEVALUE; //8bit value since its a 8bit port...

How would i clear a single bit? By clear i mean set to 0...? While preserving the rest of the bits of course.

[pasau]

lets say you wanna clear the first bit, i would go with something like this:

LEDS <: OLDOUTPUTVALUE & 0b11111110;

[AtomSoft]

I assumed that... but are you telling me i have to buffer what im putting out?

There is no way to read the current value back?

[segher]

You can also get the value currently on the pins using peek().
It is better to keep track of the value you are outputting
though, as pasau says.

[AtomSoft]

Thanks, im about to try this:

#define CLK_HIGH() SPI2 <: (peek(SPI2) | CLK)
#define CLK_LOW() SPI2 <: (peek(SPI2) & (~CLK))

[Bianco]

For a clock i'd just buffer the old value or use constants. (or use a buffered port when applicable)

[AtomSoft]

Yes its for a clock, i dont see the advantage of using a buffered port. Seems more complex at the moment. Id rather just peek like im doing now, it works as far as i can tell so im happy :)

[segher]

Disadvantages of using peek() include: a) it is somewhat
slower; b) it returns the value *currently* at the pins (so
beware with buffered ports, etc.; also, if you do it too fast
after the previous output you will need a sync on the port,
and even then you still need to consider the delay from port
output to port input); and c) it returns the value currently
at the *pins*, which is not necessarily the same thing you
are outputting (say, open drain output -- should not be a
problem with 4-bit ports unless you are overpowering the
pins somehow; bad plan that).

So yes it should work for you, but it is not the best solution.
It does make for a nice quick hack though ;-)

[AtomSoft]

ah ok, yeah i can see its usefulness ... for a 25mhz max spi i think its ok... i might use it at 10mhz tho.