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  1. #1
    Registered User
    Join Date
    Apr 2006

    Angry HELP !!! Bluetooth SPP speed : DataInputStream overflow?

    Hello everybody!

    I need help.

    I have a device that sends data (images of 20kB) at 115200 bds via an UART connected to a bluetooth module. I try to receive these data with a Nokia 6680 through a bluetooth SPP connection.
    Once I am connected, if my device sends some data (<3KB for example) I am able to receive them with the mobile. Otherwise some data are missing. It seems that the maximum data available in the stream is 512 Bytes, and this "buffer" overflows if I am not able to read the data fast enough, and that is the case. Even using the readBuffer() method.

    I thought about different solutions without success:

    - using an inputstream -> same result
    - using a bytearrayinputstream related to a 20k Bytes buffer -> how to connect it from a connector? there is no available method...
    - increase this input buffer size -> does anybody know if there is a way to do this? This would be the solution...
    - disable all hidden running threads that would occupy the system to concentrate on the data reception -> I don't know how and which ones...

    If I slow down the data flow to 57600 or 28800 bds, it still doesn't work. But it works at 9600 bds... but it's very slow... too slow... around 20 seconds!

    I must precise two things:
    - I am not far from device (<1m)
    - I am convinced it is feasible because sometimes all the data are received and the received image is correct. but this is very rare... (<10%)

    Any idea, solution is welcome!!!

    Thank you all for your help...

    Have a nice day


  2. #2
    Registered User
    Join Date
    Sep 2003

    Re: HELP !!! Bluetooth SPP speed : DataInputStream overflow?

    I have had similar problems working with bluetooth spp on the 6620 and 6682 phones. Most of the devices I work with our 9600 or 19,200 and they generally worked fine. When I tried a device that ran at 38,400 and sent a lot of data something would happend during the read process that would crash the whole app - no exception was thrown, the app just stopped. I got it working reliably by placing short sleep statements in key places during the read process. It slowed things down a little bit, but since I couldn't change the baud rate of the device I was talking to, this was the only option. It seems there's a bug somewhere in the bluetooth IO process on the series 60 phones. I think there is mention in the forums of other folks using l2cap instead of btspp and not having problems, but that only works if you control things on both sides. I use serial devices and a bluetooth to serial converter, so I couldn't change any of that.
    Hope that helps or at leasts reassures you that you're not alone or crazy.

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