Re: [avr-chat] Is it any method to avoid ADC start in idle mode?

[Rolf Magnus]

On Saturday 03 June 2006 07:51, Dmitry K. wrote:
> Hi.
>
> For me it has appeared a surprise that it is impossible
> to avoid start ADC at transition in a idle state (needed
> to reduce power consumption). MCU is ATmega168 (and 48).
> It was tryed:
>   1. Disable ADC interrapt enable:  ADIE==0
>   2. No clear ADC ready:  ADIE==0, ADIF==1
>   3. (!) Auto Trigger Mode:  ADATE==1 (with timer source)
> ==> No results: ADC starts with each 'sleep' instruction.

The datasheet says it quite clearly:

"If the ADC is enabled, a conversion starts automatically when this mode is 
entered."

This doesn't depend on auto trigger source or the ADC interrupt settings.
The solution is to simply switch the ADC off  (ADEN=0).

> Certainly, the disabling of interruption (ADIE=0) limits
> quantity of starts, but it is no matter, when external
> interruptions act in the casual manner. To stop ADC it is
> impossible: it is switched off internal AREF.
>    The most insulting, that in Auto Trigger mode it is
> impossible to obtain a regular period.

Well, you can use a timer as auto trigger source.

> I attach a small test of this.

Where?