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Re: [bluetooth-dev] Bluetooth module/serial port latency



Vladimeros,
 I presume your reading or writing to the serial port and the time in which
it sends depends on a lot of factors on Linux..
for example the number of modules in the kernel. the number of processes
running, etc. There would be no way to say that you could send out the
whole packet in 15ms. If you are using sk_buff structures and the memory
management associated with the sk_buff structure you should be able to do
it without either packet loss or packet corruption most of the times..
 If you are using the HCI driver and the UART driver interface you should
use a UART driver which uses this kind of memory management. You could use
the tp4bduart driver from www.alphaworks.ibm.com for this..though.

Hemang C S
Networking Software Group, IBM Software Labs, India,
7B1,Golden Enclave, Airport Road,
Bangalore - 560017
email ID:shemang@xxxxxxx.com
Ph no. 91-80-5267117 Ext. 3715

Think!!!!                                                   Think!!!
Think!!



Vladimeros Vladimerou <vladimer@xxxxxxx.edu> on 15/06/2001 00:45:26

Please respond to Vladimeros Vladimerou <vladimer@xxxxxxx.edu>

To:   bluetooth-dev@xxxxxxx.com
cc:    (bcc: Hemang C Subramanian/India/IBM)
Subject:  [bluetooth-dev] Bluetooth module/serial port latency




Hi everyone!

I'm using an ericsson BT Application Kit on a linux machine and I'm
trying to write my own HCI driver using the serial port.
I'm using the read() command to read from the /dev/ttyS0 file.
I need to get 32-byte packets going back-and-forth two machines
through the bluetooth modules. I need a packet to reach the destination
host in less than 15ms. Is that possible?
Right now, if I try to read from the ttyS0 file for data before the
other module starts sending it, I get errors. Some zeros get inserted
in the beginning and I lose some bytes in the end.
When I wait though for 1 second after the data was sent from the
remote module and THEN read the port, I get zero errors and no
latency.
Does anyone know what's going on here?

v v


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