In Arduino Mega, bootloader does not work when watchdog is disabled

arduinoatmegaavr

In Arduino Mega (ATMEGA2560), when I enabled the interrupts, the watchdog got overflown, so the chip restarted each time the program counter achieved the interrupt enabling line.

So I tried to disable the watchdog, setting WDTCSR_WDCE to 1 and WDTCSR_WDE to 1, and after setting all WDTCSR to 0.

But when I did this, I realized that my reset pin does not work anymore. Now when I click on it, simply does not happen anything, and I cannot load a new .hex to the chip.

I burnt the bootloader again using ICSP, but the problem still happens.

Thus, how can I fix it?

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My experience is there was 2560 bootloader provided on Arduinos (at least 2-3 years ago). Watchdog is not disabled in bootloader and because watchdog timer is not reset on non power-cycle reboot then watchdog reboot causes forever rebooting in bootloader because of timeout waiting for potential upload. You can prove it that main program starts after power cycle but not when watchdog forces reboot.

Fix was uploading non bugged bootloader.

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Electronic – Arduino Bootloader

Yes, you can reprogram the chip. I did the same when I upgraded my Arduino from a 168 to a 328 two weeks ago. The chip works great in another application.

Take note, of course, that you may need to change fuses depending on what kind of board you had and what kind of board you are moving it to. The most common, I would imagine (and the ones I had to reset) dealt with changing to the internal oscillator and setting dividers instead of using an external crystal. There is no comprehensive list of fuse changes, though, because it depends on what kind of circuit you're moving the chip to. YMMV.

--Edit-- As JohnC said, yes, reprogramming of fuses should be done BEFORE you remove it from the Arduino. Since the Arduino is fused to use an external oscillator, the chip will not do a darn thing if placed on a board without an oscillator.

Electronic – arduino – Handling timer overflow and compare interrupts in ATMega328 (Arduino)

I am not fully sure as to why, but using fast pwm mode instead of normal mode seems to fix this problem.

Use the same code, but replacing

TCCR2A = 0x00;

with

TCCR2A = _BV(WGM20)|_BV(WGM21);

I would also ask why you seem to be clearing asynchronous mode both upon entering and leaving pwm mode, but it does not seem to affect anything.

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Electronic – arduino – Handling timer overflow and compare interrupts in ATMega328 (Arduino)

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