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: bluetooth-dev-admin@lists.apple.com [mailto:bluetooth-dev-admin@lists.apple.com] 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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