Hi Bob,
Please see comments below.
Thanks, Joakim
On Feb 13, 2012, at 11:09 AM, Bob Frankel wrote:
hi joakim,
thanks for the answer.... but this raises several more
questions....
in all cases, my app is *not* running in the background; do i
have to do anything to enable "active scanning"???
No, it's always on when the App is in the foreground.
as an experiment, i *removed* my peripheral name from my
advertising PDU and instead placed it in the scan_req PDU....
but when i received the callback to didDiscoverPeripheral, my
adverstisementData dictionary did not contain the
kCAdvDataLocalName key -- as it normally does when the local
name is within the adversting PDU.... shouldn't i still see
this key, as the local name was in the scan_req PDU???
It's in a consecutive callback. First, you get what's in the advertising packet, then you get the scan response data aggregated in.
then, as a second experiment, i *added* some "service data" to
my adversting PDU following the format described in volume 3,
part C, section 18.10 of the spec -- in this case, two octets of
service ID (the same one i used in my "service ID" segment of
the PDU) plus one octect of payload.... (all of this fits
within the 31 byte limit).... but, when i now scan for
peripherals in my (foreground) app, i *never* receive a
callback!! in general, is this the way to add
'kCAdvDataServiceData' to the advertisementData dictionary???
should i be using a different 16-bit UUID??? i clearly want to
associated this data with "my service"
Not sure what is going on. Could you please send the code to use in a bug report at bugreport.apple.com.
thanks in advance
bob.
On 2/13/2012 10:22 AM, Joakim Linde wrote:
Hi Bob,
See comments below.
Thanks,
Joakim
On Feb 13, 2012, at 7:49 AM, Bob Frankel wrote:
hi,
it mentions in the BluetoothDesignGuidelines that active
scanning is not always performed.... can you elaborate
just when this is the case….
Active scanning is only performed when the App is in the
foreground.
as a use-case, suppose i have a thermostat this is
adverstising the current temperature.... if i have an
app running in the background that is scanning for a
particular service presumably implemented by the
thermostat, will i be receiving the data in the
adverstising PDU or in the SCAN_RSP PDU (or both)???
If this App is in the background you will only receive data
in the Advertising PDU.
related to this, just when will i receive a callback to
my delegate -- everytime the peripheral device
broadcasts, or only when the information in the
advertising/SCAN_RSP PDUs actually change???
This depends on what options you specify. Either we provide
it the first time we see the device, or we provide it every
time we see a packet from the device (regardless if the
content has changed or not).
finally, just how much data can i pack into the
adversting/SCAN_RSP PDUs???
The Bluetooth 4.0 spec limits the size of the advertising
packet to 31 bytes. This includes headers and delimiters. See
BT 4.0 spec for details.
thanks,
bob.
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