RE: Disabling Pagescans
RE: Disabling Pagescans
- Subject: RE: Disabling Pagescans
- From: "Keith Phu" <email@hidden>
- Date: Tue, 15 Oct 2002 11:30:35 +0900
The duration of required real-time performance can vary, but it would be
in the order of minutes.
I wrote a simple test application that sends a few bytes of data over an
RFCOMM connection from one Mac to another. Data is sent periodically
(ie every 10 ms). Two times are recorded
1) The time when RFCOMMWrite is called from the Master Mac
2) The time when the incoming data handler is called from the Slave Mac
The difference between these two times (latency) is consistently 5 ms
(plus or minus 2 ms), but every 1.28s, the difference will jump to ~40
ms.
I tried using the PageDisableTool on both machines, but this didn't
solve the problem. I looked at the Bluetooth Spec again, and found that
there's also an InquiryScan state that may be causing the periodic jump
in latency.
Any more ideas? If there is no solution, at least knowing the cause of
this periodic error would still be beneficial.
Keith
-----Original Message-----
From: email@hidden
[
mailto:email@hidden] On Behalf Of Michael Larson
Sent: Friday, October 11, 2002 11:54 PM
To: Bluetooth Dev
Subject: Re: Disabling Pagescans
There is not an API available for this function at this time.
What is the duration of your real-time application - IE is it needed
for a matter of seconds, minutes, or hours?
-larson
On Friday, October 11, 2002, at 12:37 AM, Keith Phu wrote:
>
I'm trying to use Bluetooth for a real-time application, and it's
>
important that the latency and jitter of transmissions are fairly
>
consistent. Mostly, the Mac Bluetooth stack performs well ( < 10 ms
>
latency), but periodically the latency of my transmissions will jump
to
>
over 50 ms. This happens approximately every 1.28 seconds. Looking
>
through the Bluetooth specification, I think that the Bluetooth device
>
is entering the PageScan state and delaying my transmissions.
>
>
Is there a way to temporarily disable a bluetooth device from entering
>
the PageScan mode? In the spec, it mentions that the page scan
>
interval
>
can also be configured to have a maximum of 2.56s (on page 97 of the
>
Bluetooth Specification). This would help, but being able to manually
>
disable and enable page scans would completely solve my problem.
>
>
In the Bluetooth API, there's the function,
>
IOBluetoothDeviceGetPageScanMode, so I can retrieve the page scan mode
>
for a device, but I don't see any ways to set or disable it.
>
>
Does anyone have any ideas? Or is there no way to prevent page scans?
>
>
Keith
>
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