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 Posted: May 11, 2012 - 01:35 PM |
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Joined: Jan 21, 2010
Posts: 49
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Hi all,
I found many posts with this subject, but none seems to help me. I am porting my bootloader from ATmega8A to ATmega164A. I found out that the micro resets itself even if I disable the watchdog and stops to do so if I periodically reset the watchdog timer. What could I check to find out where the problem is?
I attach my code. If I comment "wdt_reset()" I see PB3 continually going up and down...
I don't see significant differences between Atmega8a and Atnega164a to explain this strange behaviour...
Any help would be greatly appreciated!
Luca
Code:
void __jumpMain (void) __attribute__ ((naked)) __attribute__ ((section (".init9")));
void __jumpMain(void)
{
SPH = (RAMEND) >> 8;
SPL = RAMEND & 0xFF;
asm volatile ( "clr __zero_reg__" ); // r1 set to 0
asm volatile ( "rjmp main"); // jump to main()
}
int main() {
uint16_t c;
general_init(); // sets PB3 as output
PORTB|=(1<<PB3);
Set_Timeout(_INIT_WAIT_);
wdt_disable();
if(eeprom_read_byte((uint8_t *)EEPROM_GOODAPP_ADDR) != MARK_FOR_UPDATE)
{
while( Get_Timeout() && (rx_index!=6) ) // I stay 5s in boot mode
{
if ((c = getchar()) != EOF)
{
buf[rx_index] = (uint8_t) c;
rx_index++;
if (rx_index == 1)
initCrc();
if (rx_index<=_EOH_INDEX_)
{
update(c);
}
else
{
if (rx_index<=_EOH_INDEX_+buf[_LENGTH_INDEX_]+1)
update(c);
}
}
Dec_Timeout();
wdt_reset(); // Reset wdt
}
}
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Posted: May 11, 2012 - 02:12 PM |
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Joined: Jul 18, 2005
Posts: 62220
Location: (using avr-gcc in) Finchingfield, Essex, England
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Quote:
I don't see significant differences between Atmega8a and Atnega164a to explain this strange behaviour...
Really? Did you read the paragraph starting "Note that for newer devices..." on this page of the manual:
http://www.nongnu.org/avr-libc/user-man ... chdog.html |
_________________
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Posted: May 11, 2012 - 03:05 PM |
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Joined: Jan 21, 2010
Posts: 49
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| oops... I did not. Thanks very much! |
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Posted: Jun 20, 2012 - 08:16 AM |
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Joined: Jan 21, 2010
Posts: 49
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Hi all,
unfortunately I still have problems with the watchdog. I modified my code adding this lines at the beginning:
Code:
MCUSR = 0;
wdt_disable();
I added this lines at the beginning of the main function in both my bootloader and user code. I just use the watchdog to go to boot from the user code, but sometimes I observe unexpected resets and monitoring MCUSR I find out they are due to watchdog. Shouldn't it be enough the code I wrote to disable the watchdog?
I have not set the WDTON fuse.
Thanks,
Luca |
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Posted: Jun 20, 2012 - 08:45 AM |
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Joined: Mar 28, 2001
Posts: 20325
Location: Sydney, Australia (Gum trees, Koalas and Kangaroos, No Edelweiss)
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| Maybe a optimisation issue? What level are you using? I think the the WDT requires a precise number of cycles to be disabled. |
_________________
John Samperi
Ampertronics Pty. Ltd.
www.ampertronics.com.au
* Electronic Design * Custom Products * Contract Assembly
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Posted: Jun 20, 2012 - 08:50 AM |
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Joined: Jan 21, 2010
Posts: 49
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I am using the -O2 optimization. I try to check out if this is the problem.
Thanks,
Luca |
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Posted: Jun 20, 2012 - 09:53 AM |
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Joined: Jan 21, 2010
Posts: 49
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I tried with -O1 and the reset occurs again. The strange fact is that I don't get a reset immediately, but after some minutes of code execution.
Furthermore, I read this passage in the datasheet:
Quote:
If the Watchdog is accidentally enabled, for example by a runaway pointer or brown-out
condition
So, I don't understand, can a Brown-out enable the watchdog? Is it possible that a brown out reset is seen as a wdt reset through the MCUSR?
Thanks,
Luca |
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Posted: Jun 20, 2012 - 10:02 AM |
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Joined: Jul 18, 2005
Posts: 62220
Location: (using avr-gcc in) Finchingfield, Essex, England
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| In brownout any register in the AVR might assume random values and I guess that includes WDT. As long as you have the BOD fuse set you should not be subject to brown out anyway. |
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Posted: Jun 20, 2012 - 10:18 AM |
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Joined: Jan 21, 2010
Posts: 49
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I have BOD set to 4.3V and my power supply voltage is stable at 4.8V (+-0.1V due to the switching regulator resistors tolerances).
Anyway, I always see the reset source as 0x04, so it seems to be deterministic... |
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Posted: Jun 20, 2012 - 10:36 AM |
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Joined: Mar 28, 2001
Posts: 20325
Location: Sydney, Australia (Gum trees, Koalas and Kangaroos, No Edelweiss)
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Quote:
the reset source as 0x04
That's not the wdt but the BOD resetting then.
MCUSR
Code:
JTRF WDRF BORF EXTRF PORF
0x08 0x04 0x02 0x01
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_________________
John Samperi
Ampertronics Pty. Ltd.
www.ampertronics.com.au
* Electronic Design * Custom Products * Contract Assembly
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Posted: Jun 20, 2012 - 10:41 AM |
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Joined: Aug 21, 2002
Posts: 895
Location: Austria
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I would never set the BOD level so close to the supply voltage. AFAIK, VBOT(4.3V) is 4.1V to 4.5V.
Very likely a short drop on Vcc (maybe a response to a change in current consumption) will drigger BOD.
Do you have proper decoupling caps on the supply pins of your AVR?
Try to set BOD to 2.7V. |
_________________
/Martin.
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Posted: Jun 20, 2012 - 10:59 AM |
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Joined: Jan 21, 2010
Posts: 49
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I think you are right, I'll change the BOD setting to 2.7V. Thanks,
Luca |
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