AT%SLEEP=n power consumption

[Joerg Reisenweber]

Am Mo  20. Oktober 2008 schrieb Alastair Johnson:
> Werner Almesberger wrote:
> > I order to evaluate the impact of the AT%SLEEP=2 work-around, Joerg
> > asked me to measure how the sleep mode affects the current drawn by
> > the system.
> > 
> > Test setup:
> > 
> > - device is idle but (for convenience) not suspended
> > - GSM is active and has registered with the network (AT+CFUN=1,
> >   AT+COPS=0)
> > - the test setup does not suffer from #1024
> > - power is supplied to the battery terminals from a lab power supply
> >   set to 4.0V
> > - USB is not connected
> > 
> > Battery current of the whole system in mA. Values are from measurements
> > averaged over about 15 minutes each:
> > 
> > at%sleep=       avg     min     max     samples
> > 4                96.0    91.6   198.0   20006
> > 3                98.4    91.6   214.6   21432
> > 2               102.2    97.6   209.3   21428
> > 1               104.0   101.9   197.2   21352
> > 0               120.3   118.8   213.0   21452
> > 
> > Integration period is one power line cycle (20ms). There are transients
> > much faster than 50Hz. E.g., sampling at 2.5kHz finds more noise but
> > does not change the difference in the averaged value:
> > 
> > at%sleep=       avg     min     max     samples
> > 4                95.1    63.1   242.5   210207
> > 3                97.1    62.8   242.9   215460
> > 2               101.4    68.7   243.4   208230
> > 
> > Note that this is an idle but not suspended system, hence the large
> > minimum current.
> > 
> > So the difference between sleep=2 and sleep=4 is about 6mA. Joerg
> > mentioned that the idle current of the GSM subsystem should be 4mA,
> > so this would be an increase to 250%.
> > 
> > Andy, you once measured the power consumption when the overall system
> > is perfectly suspended. Do you still remember how much it was ?
> > 
> > - Werner
> 
> Can you repeat the test on a handset that is suffering from #1024? I 
> suspect that the frequent reregisters increase power consumption, but I 
> don't have the equipment available to make the measurements. It 
> certainly produces more instances of GSM interference on my PC speakers 
>   which suggests more transmit operations. If this is the case then for 
> those wth #1024 SLEEP=2 may be no worse, or possibly better, than SLEEP=4.

that's the idea behind Mickey's recent bandaid, switching to SLEEP=2 on 
detecting #1024 behaviour
/j
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