I'm encountering a strange error with avr-gcc 4.6.3 and 4.7.2 using the timer interrupt. The code I'm using is attached. As you can see, I was trying to tie in to the Arduino environment (with Eclipse) so that I could help my students wean off that set of functions to being able to use the hardware directly.
When I set up the library, I encountered a strange error and was able
to trace it back to this simple program that sets up the timer with a
prescalar of 1024 and then increments an unsigned long counter when
that timer overflows. When the counter reaches a specific value, I
toggle the built-in LED on the Arduino board connected to PORTB.
The strange behavior is that if I initialize the counter to 0, the
code doesn't work--appearing to hang. If I initialize the counter to
1, everything works perfectly. I have verified that if I make a
similar change to the Arduino libraries that the original code begins
to work properly.
I'm not sure what the exact error is since I can use the Arduino
environment on my machine without a problem, but when I try to compile
it through Eclipse it gives me this error. I'll include the build log
as an attachment in case particular compiler/linker flags are triggering
the error.
-- Jonathan Geisler --
/*
* main.cpp
*
* Created on: Feb 8, 2013
* Author: Jonathan Geisler
*/
//#define JGG
#ifdef JGG
#include "Arduino.h"
#else
#include <avr/interrupt.h>
#endif
void setup() {
#ifdef JGG
pinMode(13, OUTPUT);
#else
TCCR0A = 0;
TCCR0B = 5;
TIMSK0 = 1;
sei();
DDRB |= 0x20;
#endif
}
volatile unsigned long count = 1; // bad executable if initialized to 0!!!
void loop() {
#ifdef JGG
digitalWrite(13, HIGH);
delay(1000);
digitalWrite(13, LOW);
delay(1000);
#else
if (count > 50) {
PORTB ^= 0x20;
count = 0;
}
#endif
}
#ifndef JGG
ISR(TIMER0_OVF_vect) {
++count;
}
void init() {
/* do nothing */
}
#endif
int main() {
init();
#ifdef USBCON
USBDevice.attach();
#endif
setup();
while (1) {
loop();
}
}
make all Building file: ../main.cpp Invoking: AVR C++ Compiler avr-g++ -I"/home/jgeisler/src/eclipse/Arduino_Core/src" -DARDUINO=103 -Wall -Os -ffunction-sections -fdata-sections -fno-exceptions -mmcu=atmega328p -DF_CPU=16000000UL -MMD -MP -MF"main.d" -MT"main.d" -c -o "main.o" "../main.cpp" Finished building: ../main.cpp Building target: Arduino-on-Eclipse-1.elf Invoking: AVR C++ Linker avr-gcc -Wl,-Map,Arduino-on-Eclipse-1.map,--cref -Wl,--gc-sections -Os -L"/home/jgeisler/src/eclipse/Arduino_Core/328P_16MHz" -mmcu=atmega328p -o "Arduino-on-Eclipse-1.elf" ./main.o -lArduino_Core -lm Finished building target: Arduino-on-Eclipse-1.elf Invoking: AVR Create Extended Listing avr-objdump -h -S Arduino-on-Eclipse-1.elf >"Arduino-on-Eclipse-1.lss" Finished building: Arduino-on-Eclipse-1.lss Create Flash image (ihex format) avr-objcopy -R .eeprom -O ihex Arduino-on-Eclipse-1.elf "Arduino-on-Eclipse-1.hex" Finished building: Arduino-on-Eclipse-1.hex
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