 |
| Author |
Message |
|
|
 Posted: Mar 30, 2012 - 06:12 AM |
|
Joined: May 02, 2010
Posts: 23
|
|
Hi all,
I must be missing something very simple here. I've got an Atmega128 hooked up on my STK600. PORTA is connected to the LED's. Nothing else is connected. For some reason setting other ports to output in an external function seems to screw things up.
first LED off = YIPEE!
first LED on = WTF?!?
Code:
#include <avr/io.h>
// function prototype(s)
void initializeDisplay(void);
int main(void) {
initializeDisplay();
PORTA = 0x01;
}
void initializeDisplay(void) {
DDRA = 0xff;
// DDRB = 0xff;
}
= YIPEE!
Code:
#include <avr/io.h>
// function prototype(s)
void initializeDisplay(void);
int main(void) {
initializeDisplay();
PORTA = 0x01;
}
void initializeDisplay(void) {
DDRA = 0xff;
DDRB = 0xff;
}
= WTF?!?
Code:
#include <avr/io.h>
int main(void) {
DDRA = 0xff;
DDRB = 0xff;
PORTA = 0x01;
}
= YIPEE!
Hurrrr? |
|
|
| |
|
|
|
|
|
|
Posted: Mar 30, 2012 - 06:48 AM |
|
Joined: Nov 22, 2002
Posts: 12055
Location: Tangent, OR, USA
|
|
Not sure if this is a problem, but I not expect the ports to be in any predictable state after the code exits from main. It will execute your code and be done in a few microseconds - far to fast for you to even see what happens.
At the very least, I would do
Code:
#include <avr/io.h>
int main(void) {
DDRA = 0xff;
DDRB = 0xff;
PORTA = 0x01;
while (1) {
}
}
Jim |
_________________
Jim Wagner
Oregon Research Electronics, Consulting Div.
Tangent, OR, USA
"The only thing standing between us and victory is defeat" P.G.Wodhouse in Wooster & Jeeves series
|
| |
|
|
|
|
|
|
Posted: Mar 30, 2012 - 07:13 AM |
|
Joined: Nov 17, 2004
Posts: 13852
Location: Vancouver, BC
|
|
avr-gcc puts an automatic while(1) at the end of main, so it shouldn't make a difference. If you were using interrupts, then that would be a different matter since it also puts a cli() just before the while(1).
I suspect that the real problem is that you didn't clear the mega103 compatibility fuse (the mega128 comes from the factory with it set). Because of this, the function call returns to a random address since the stack pointer is set incorrectly. Either clear the fuse, or compile for a mega103. |
_________________
Regards,
Steve A.
The Board helps those that help themselves.
|
| |
|
|
|
|
|
|
Posted: Mar 30, 2012 - 03:16 PM |
|
Joined: May 02, 2010
Posts: 23
|
|
| Yup, that did it. Thanks Koshchi! |
|
|
| |
|
|
|
|
|
|
|
FAQ
Search
Register
Log in to check your private messages
Log in
Maximize
RSS
