I have an application in which I use
Bluetooth to wirelessly control a robot which also supports Bluetooth.
The user can use the keyboard arrows/space bar to drive the robot around
and shoot balls much like they would a First Person Shooter video game.
The application works great on Macs
with a built-in Cambridge Silicon Bluetooth chip. However, it is dismally
slow on the more recent Macs with the Broadcom part. This seems to include
MacBook Pro (2008 or later) and MacBook Air. There is so much lag between
when the user pushes an arrow key and when the robot responds that the
robot is completely uncontrollable. However, if I use a USB Bluetooth dongle
that has a Cambridge Silicon part in it, everything works great.
This would indicate that either the
Broadcom part or Apple's implementation of the stack for Broadcom have
major performance problems.
My application calls IOBluetoothRFCOMMChannelWriteAsync
and then looks for the IOBluetoothRFCOMMChannelEventTypeWriteComplete event.
With the Cambridge Silicon part it takes
an average of 12.8ms for the Event to come.
With the Broadcom part, it takes and
average of 231ms.
This is 20 times longer!
(see the Packet Logger trace attached
- tab 1 for Cambridge Silicon, tab 2 for Broadcom).
After finding this, I found at least
3 different forums where people had reported major performance problems
with Bluetooth applications when they switched to newer Mac hardware which
seems to corroborate my findings.
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