[Interest] Interest Digest, Vol 53, Issue 19

[Dmytro Haponov]

what is the right way to communicate up here?

about BLEscanner:

Blasche Alexander, I'm on Ubuntu 15.10 x86 - and it's 7-8 mins for this
cache to renew. Is that the same cache that QBluetoothDeviceInfo has method
                 bool isCached() ? - 'cos it returns false to me about any
ibeacons all the time - whether they're in range or not.

What's even worse - I can't get the real picture of what ibeacons are in
range for the moment even in case of constantly deleting and creating new
deviceDiscoveryAgents! When the new one is created its discoveredDeviced
list is empty, but as soon as I start() the agent - its list of discovered
devices is not empty!!

It simply returns rssi == 0 for the devices it had already seen and there's
no way to know - whether that ibeacon is now in range or not...

I believe bluez has nothing to do with it as I can always get the right
info with "sudo hcitool lesan"

On Sat, Feb 20, 2016 at 1:40 PM, <interest-request at qt-project.org> wrote:

>
> ---------- Forwarded message ----------
> From: Dmytro Haponov <dmytro.haponov at gmail.com>
> To: interest at qt-project.org
> Cc:
> Date: Fri, 19 Feb 2016 14:16:13 +0200
> Subject: [Interest] lowEnergyScanner detects ibeacons that are absent
> after creating this topic
>
> https://forum.qt.io/topic/64355/lowenergyscanner-example-shows-absent-devices/2
> I was advised to address the question here.
>
> The general question is - how to actively scan for BLE devices that are
> present at the moment of scan?
>
> Dmytro Haponov
>
>
> ---------- Forwarded message ----------
> From: Blasche Alexander <alexander.blasche at theqtcompany.com>
> To: "interest at qt-project.org" <interest at qt-project.org>
> Cc:
> Date: Fri, 19 Feb 2016 12:57:59 +0000
> Subject: Re: [Interest] lowEnergyScanner detects ibeacons that are absent
>
> The delay between the device disappearing and the scan results being
> adjust is caused by caching in the Bluetooth stack. On Bluez the default is
> 2 or 3 mins for cache expiry. I have no data about other platforms. What
> platform are you on?
>
>
> In fact in some cases the caching goes even further. Sometimes the details
> of the disappeared device are cached and when you connect you get data from
> the cache or the list of the services. This doesn't work on Bluez but I
> have seen this behavior on WinRT for example.
>
>
> Unfortunately, there is not much you can do about it.
>
> --
>
> Alex
>
>
>
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