AVR-Chat

On 02/05/2010 17:41, anickol wrote:
>
> Hello.
>
> I've ran into a problem that I do not know how to solve.
> It seems that under some conditions ATTiny devices hang during reset.
> It happens not at every start, it seems to be a relativeky rare case.
> But it happens. I've seen it with ATTiny13V and ATTiny2313 so far.
>
> How it is done. The power line has 100uF electrolytic capacitor and a decoupling ceramic 1uF one near the Atmel device. The reset circuit has 10 KOhm resistor to +5V. At start the controller sometimes is in unpredictable state, sometimes the pins are low, sometimes high.
> Watchdog timer DOES NOT always reset the device, even if WDTON is programmed.
>
> The device is working as a high current PWM controller, so the power line is not perfect. However, I've never seen it hang if it managed to start.
>
> Out of about 100 power-on attempts about 10 ended in unpredictable state and other 20 were resetted by WDT. Other 70 went normal.
>
> Applying external Reset when the controller hangs restores normal operation, however simple R-C reset circuit does absolutely nothing.
> I tried various C and R combinations, but they did not reduce or increase the number of fails.
>
> Other odd thing is that failures seems to appear in groups. Once it hangs, it will most probably hang again next time.
>
> What is going wrong ?


You are probably getting transients from whatever you are controlling 
affecting the AVR.

Leon
-- 
Leon Heller
G1HSM