From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <506AEDFC.9060300@rug.nl> Date: Tue, 02 Oct 2012 15:37:00 +0200 From: Sietse Achterop MIME-Version: 1.0 To: linux-bluetooth@vger.kernel.org Subject: Unreliable communication with multiple bluetooth devices and some delay Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Dear list, not sure wheather this for this list, but if so please tell me. I have problems with unreliable bluetooth communication. I have 7 bluetooth devices (epucks, educational robots: http://www.e-puck.org/). They use the lmx9838 device for bluetooth and are seen as rfcomm-devices on linux. The lmx-device is used in transparent mode. This is on various linuxes, with kernels 2.6.32, 3.0.0 and 3.2, e.g. as in the latest ubuntu 12.04.1. The test program is a simple loop that continuously sends each epuck a small message, a string of say 6 characters. I use stdio's fprintf to send chars to the /dev/rfcomm devices. In pseudo code: open_devices(); while true do for i = 1 to 7 do fprintf(fp[i], "l,1,2\n"); od delay( 0.5 seconds); od This works perfectly if the delay statement is REMOVED. Then each 2 milliseconds a message is send to the next epuck. But if the delay is ADDED again it gets very UNRELIABLE. After 1 to 30 seconds a communication is failing and after a 20 second delay the connection of a epuck is dropped. After a longer time all connections are dropped. I tried a lot, but am at a loss at the moment. The question is, where the problem. Why is the delay the problem? Are the short messages the problem? Is it a bug in the linux driver? Hopefully someone on the list can help me a step in the right direction. Thanks in advance. Sietse Achterop University of Groningen The Netherlands