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Last Post 18 Apr 2016 05:08 PM by  Adam Ford
Bluetooth data speed drop
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Bevis Peters
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06 Apr 2016 10:44 AM

    We have found that in our latest system, based on the 2.4-4 BSP, we are seeing a massive drop in bluetooth data rates compared to our previous system based on 2.2-2 BSP - using 2.2-2 we saw around 35KB/s, with 2.4-4 we are seeing 7KB/s (this is using rfcomm).

    We have the change in mach-omap2/board-omap3logic.c to set ".baud_rate = 3000000" in both versions.

    We are using bluez2 in both versions, though we see no difference when using bluez4 instead.

    We have tried repeating this with your demo BSP for both 2.4-4 and 2.2-2 and see rates of around 7KB/s in both cases; I don't know if your demo BSP images have the ".baud_rate = 3000000" patch applied.

     

    Do you know why we are seeing such low speeds in 2.4-4 compared to 2.2-2 ?   We are using the -31 torpedos in all cases.

     

    bevis

     

     
    Bevis Peters
    New Member
    New Member
    Posts:6


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    06 Apr 2016 11:02 AM
    For info I have also measured the bluetooth data rates on a few demo BSP versions:

    2.4-4 = 7KB/s
    2.4-3 = 18KB/s
    2.4-2 = 7KB/s
    2.2-2 = 7KB/s

    it's curious that the rate improved for 2.4-3 and then dropped back again.
    Bevis Peters
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    Posts:6


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    12 Apr 2016 07:14 AM
    Can noone help with this?
    Adam Ford
    Advanced Member
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    Posts:794


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    13 Apr 2016 06:50 AM
    Sorry, I was out of the office for a few days and unable to respond.

    We didn't make any changes to the Bluetooth drivers that I can see between 2.4-2 and 2.4-4. There is a performance kernel option inside LTIB. This eliminates some debug options which lowers the overhead. We found that helped improve the WiFi and Ethernet throughput.

    In ltib if you change the (omap3logic_defconfig) kernel preconfig to (omap3logic_defconfig-performance) kernel preconfig it may increase throughput.

    Can you give me some background on how you're measuring the throughput?

    adam
    Bevis Peters
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    Posts:6


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    14 Apr 2016 03:03 AM
    My apologies - this came down to user error.
    In our code I had believed that I had included the "baud=3000000" patch to board-omap3logic.c, but closer investigation showed that it was being overwritten with the original file during the build process itself.

    I presume therefore that the demo BSPs do not have the baud mod applied.


    bevis
    Adam Ford
    Advanced Member
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    Posts:794


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    18 Apr 2016 05:08 PM
    I was reviewing the source, and it appears as if the default is 115,200, but I thought it was increased to 3M. I have sent out an internal e-mail to one of my colleagues to see if he remembers.

    I did some through-put testing on the Bluetooth and I'm trying to find the data rates I was able to achieve. I will publish them when I find them.

    adam
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