Re: Battery Usage - Connect vs. Scan - App in Background
Re: Battery Usage - Connect vs. Scan - App in Background
- Subject: Re: Battery Usage - Connect vs. Scan - App in Background
- From: Michael Farley <email@hidden>
- Date: Wed, 03 Apr 2013 12:07:46 -0700
Steve,
Thanks for the quick response. I'm not concerned about discovery
times, I've got that under control.
My main concern is how much battery will be drained when I'm trying to
see if a device is within range. I see two ways:
1) Scan for the device
2) Issue a connect request to the device
Is the radio's receiver going to be on for the same amount in each
scenario? Or will one cause the radio to be on more than the other?
Or, are there more battery consumption factors than the receiver being
on or off (e.g. maybe if you set the radio to on but only searching
for a specific BLE device, it uses less power)?
Regards,
Mike
On Mon, Apr 1, 2013 at 2:32 PM, Stephen Jablonski <email@hidden> wrote:
> Hi Mike,
>
> I can't speak in exact battery consumption, but I can tell you that from our tests in the past that neither had a significant impact on our battery life at all. Even better, when our test iPod Touches are in peripheral mode we've had them last for many days in the background without draining the battery (only app running at the time). I would like to assume that in a central role you would see much the same. BTLE is meant to be run at a very low power consumption.
>
> As for the discovery time… it varies. iOS ramps up and down the amount of times it listens depending if your app is in the foreground or background. There is no exact number. If you ramp up the advertising rate on your peripheral device it will connection much faster. In our test cases we saw anything from 5 seconds to 40. It all depends on the you listening at the same time your advertising. That will always change.
>
> Hope that helps. Sorry that there is no "conclusive" numbers.
>
> - Steve Jablonski
>
> On Apr 1, 2013, at 5:23 PM, Michael Farley <email@hidden> wrote:
>
>> What is the most power efficient way to find out a known BLE device is
>> within range, while the app is in the background? Please assume that
>> the BLE device has not been seen during this background scan (i.e. I'm
>> aware of no-duplicates when you're in the background). iOS device is
>> the central device, and the "BLE device" is the peripheral.
>>
>> I already have the UUID of said BLE device, so I can issue a
>> connectPeripheral(). Alternatively, I could issue a
>> scanForPeripheralsWithServices() to find the device. Is one better
>> than the other in terms of iOS battery consumption? How about
>> "discovery" time (i.e. would I get a didConnectPeripheral() call
>> faster than I would get a didDiscoverPerpheral() call)?
>>
>> Thanks in advance,
>> Mike
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