> On Sun, Dec 7, 2008 at 5:10 PM, solarwind <x.solarwind.x@gmail.com> wrote:
>> All I need is a simple example how to get the interrupt on pin change
>> to work. There aren't many C examples for this.
>>
>
> Do you understand how PIC interrupts work yet?  (not being snide here,
> you're learning and that's cool.)
>
> C example will be very similar to the assembler.  You'll want to learn
> the "set register" and "set/clear a single bit" instructions, at
> least, to understand the datasheet examples.   The actual interrupt
> handler tends to vary by compiler; consult the manual for the compiler
> you are using.

Again, you do *not* actually need to use an interrupt handler, nor globally 
enable interrupts to get interrupt-on-change to work to wake up from sleep.

As Olin noted, an enabled interrupt-on-change causes an interrupt 
*condition*, but it only becomes an actual interrupt if interrupts are 
globally enabled.

So, you want to do the following:

1: Make sure you properly initialize your inputs as digital as opposed to 
analog (often controlled by a port called ANSEL, but this varies amoung 
several different PICs).

2: Make sure your inputs are set up as inputs rather than outputs (this is 
the default condition, check out TRIS registers for this).

3: Make sure that interrupts are globally disabled (often a flag bit called 
GIE). This is the default condition.

4: Make sure the interrupt-on-change interrupt is enabled (another flag 
bit).

Now a SLEEP should be terminated when the input bit changes, but no 
interrupt handler is needed.


Some baby steps:

I would start by trying to write a program that just copied the state of an 
input bit to an output bit. This makes sure you have inputs set up as inputs 
and outputs as outputs. Then I would try to add the 
interrupt-on-change/wakeup from SLEEP logic.

-- Bob Ammerman
RAm Systems


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