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Analog loopback latency

leargaf
Prodigy 30 points

Hi

I have a PADK board with a C6727 DSP. I'm running an example analog loopback project that came with the board. It uses MCASP to produce an echo from analog input to analog output. The problem is latency seems to be too high, around 1.5 ms when sampling one frame at 192 KHZ. Is there a way to reduce this latency?

 

Thanks,

Rafael

 

  • 0
    TI__Mastermind 18130 points

    Hi Rafael,

    I have not tinkered with the AnalogLoopback example in a while, but if memory serves you should be able to drop the latency by reducing the size of the frame buffer. I think it is called FRAME_SIZE, and by default it is something like 100 samples. The larger the buffer size, the longer it takes to receive/fill and transmit/empty; however, keep in mind that smaller buffer sizes means you will see more total overhead caused by interrupts and such.

  • 0 in reply to TimHarron
    Prodigy 30 points

    Thanks Tim,

     

    I alredy tried reducing the frame size. With the smallest frame size I still get the 1.5 ms latency. The is another problem, that might be related. There is another example called echo that uses DSP BIOS, but it doesnt work and trying to launch the CPU load graph fails reporting an incompatibility between RTA plugin ( I have version 4.90) and BIOS version (I have 5.20 ). Is there a way to upgrade the RTA plugin?

    Thanks,

    Rafael

     

  • 0 in reply to leargaf
    TI__Mastermind 18130 points

    Open up Help->About and check which version of DSP/BIOS you have loaded. If you have v4.90 loaded (which is the default for CCS v3.1) then you will need to download version 5.20.xx from here. BIOS did not support the C672x processors until BIOS v5.20, so you will need to use something in the v5.20.xx range at a minimum.

    If you do need to install a newer version of BIOS you will then need to tell CCS to use the newer version in the Component Manager (again in Help->About). Expand the DSP/BIOS section, then the C67xx section and click the box next to the 5.20.xx version you install. After this restart CCS and you should be all set.

  • 0 in reply to TimHarron
    Prodigy 30 points

    According to Component Manager I'm using DSP/BIOS 5.20 and RealTimeAnalysis 4.90.00.1 plugin. I have CCS v3.3.

    Thanks,

    Rafael