Embedded PIC C programming

[shamone]

Hey guys, I was wondering if anyone could direct me to a site that explains, in detail, embedded C programming for PIC microcontrollers. I am trying to learn how to manipulate data on PORTS such as see if a switch has been pressed and stuff like that. It seems quite trivial and i can do it in assembly but i am a little confused. Any help would be appreciated.

 

[MikeHalloran]

Did you know that switches 'bounce'? I.e., go on and off, briefly, perhaps hundreds of times, before assuming a stable state? Dealing with that well requires nontrivial code, in any language.

{
Personally, I would program a PIC in C only if "tied to a horse, and dragged forty miles ... by my tongue". Perhaps you have other incentives.
}

What about the documentation that came with your C compiler? And all the stuff on the Microchip CD?






Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[shamone]

So what you are saying is that you enjoy itP-). I am just re-learning my C code as i haven't done it in awhile and i am familiar with PIC's back in my school days. So it is just for educational purposes. And yes I am aware of bouncy switches.

 

[richs]

To MikeHalloran-

Hi Mike-

You might want to do a google search on "cc5x" and revisit
the C compilers for PICs.

It's a freebie that runs on Windoze, but aside from that
limitation, it isn't too bad.

As an evaluation example, I did a "geek-clock" with it using
my favorite mid-level pic, 16f648A.

Turns out that although there were some differences and
implementation details (some of the K&R C code didn't
compile and had to be worked around) it came up pretty
clean.

With the "freebie" package, you get a floating point math
package (although not the complete package) and can have
oddles of fun with it for no investment.

The code is surprisingly compact and with the mixed listing,
I found it to be very easy to use with the microchip
simulator.

YMMV, of course, but I think that it will be a tool that I
will keep in my toolbox.

Cheers,

Rich S.

 

[MikeHalloran]

I've lost count of the hours I've spent chasing bugs that were 'my fault', because I didn't know about one weird behavior or another of C or its accursed preprocessor.

I'd much rather deal with a language whose behavior can be completely described in one paragraph; FORTH. Or, no language at all, just a decent assembler that does what it's told to do.





Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[Madcow]

Down load the c18 compiler and look at the examples.

Here is a read and a write to port b. write commented out.

#include <p18cxxx.h> /* for TRISB and PORTB declarations */

/*
void main (void)
{
TRISB = 0; //sets port b as all outputs
PORTB = 255; //set port b bits
}
*/
int buttons;

void main (void)
{
TRISB = 255; //sets port b as all inputs
buttons = PORTB; //read port b bits
}

 

[richs]

"behavior or another of C or its accursed preprocessor"

One man's pleasure is another man's poison.

I've used the C preprocessor quite a number of times all
by itself to manipulate data and find it a blessing.

Each to his own.

Cheers,

Rich S.

 

[shamone]

Yah that is what i think, thanks guys, it is all coming back slowly. Got some books on theway which help me out.

Cheers