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2.1 configuration for Slave missing

Pawel Piwowarski87949
Intellectual 825 points

I am finalizing quite ambitious commercial audio project and one of its important features is HD audio quality over radio link using CC85xx. It is, however, only possible using 2.1 PCM configuration. For over two years I have lived in belief it is possible using CC85xx as I checked this configuration in PPC.  Now I am ready to testing and it has turned out it is probably not going to work since it is possible on the Master side.as I checked but it has just turned out to my great dissapointment that 2.1 config is not available on the Slave  ... I understand my config, i.e. 2.1 Master to 2.1 Slave is not one of the "use cases" defined by CC's designers. But the bandwidth is there, the firmware modification is slight if any - could you please add 2.1 configuration option to PPC on teh Slave side ? There is already a 2/1 Slave config available that allows to configure 3xPCM16 so the only change is 2.1 output channel instead of 2 out/1 in.

I would also like to remind of my earlier post and question also concerning the 2.1 mode - the user guide discourages from using it - what practical disadvantages or negative impacts I should count with when using it ?

As this issue seems quite straightforward to address while it is quite important for my business success in using  CC85xx chips I would appreciate an answer possibly soon here or even better directly by e-mail off-the-forum.

Thanks, Pawel

  • 0
    TI__Mastermind 21125 points

    Hi Pawel, 

    Locate this folder on your PC:
    C:\Program Files (x86)\Texas Instruments\PurePath Wireless Configurator\application_roles\

    These xml files can be edited in any text editor (xml syntax helps but is not needed). They define the application roles supported and you are free to add the missing config. Making a 2.1 slave should be quite straight forward, Made an attempt that I have attached here. Add this to your <My Documents>\Texas Instruments\PurePath Wireless Configurator\application_roles (added here as uninstalling the tool or installing a future version of the config will re-write the original path) and restart the configurator and you should be able to select this for your slave. 

    Please note that this specific configuration has not been thoroughly tested, but as you state the BW is there (headset streaming roles). Even though the config file allow for 3 PCM16, you would get a more robust link if you select PCMLF for the .1 channel.

    Hope this helps. 

    Kjetil 

    s_2_1_output_satellite.ppward
  • 0 in reply to Kjetil
    Intellectual 825 points

    Hi Kjetil,

    thanks a lot for the prompt response with a solution, I followed the instructions and I can see the config for slave i PPC. I shall test it in the next 2-3 weeks and report back here.
    As for the robustness in 3xPCM16 - it seems the current "robust" audio bandwidth is somewhere around 1,8 Mbit/s whereas for 3xPCM around 2,3 Mbit is required. Is it somehow a hard set limit in your design or it is open and can be improved in near future as I presume a strong team of designers and developers is working on PurePath on an ongoing basis ?

    Regards, Pawel

  • 0 in reply to Kjetil
    Intellectual 825 points

    An additional question - for my application it would bee good to have the option of switching application role config - between 2.0 and 3.0 depending on the working mode - is it possible somehow programatically in the runtime ? Or the general rule is anything that is configured in PPC cannot be modified in runtime ?

  • 0 in reply to Pawel Piwowarski87949
    TI__Mastermind 21125 points

    As for the robustness in 3xPCM16 - it seems the current "robust" audio bandwidth is somewhere around 1,8 Mbit/s whereas for 3xPCM around 2,3 Mbit is required. Is it somehow a hard set limit in your design or it is open and can be improved in near future as I presume a strong team of designers and developers is working on PurePath on an ongoing basis ?



    This is not a hard limit per se and the fact that you are able to select 3 channels PCM16 in the configurator without getting an error shows that the limit is at least 2,3 Mbit. The limiting factor is that the configurator will calculate the protocol timing for any given configuration and in case there is not room timingwise for at least one re-transmission (simplified..there are a few other things it checks as well) it will flag this either as disabling some choices in configurator or come with a warning that something is below the critical level.  The team is constantly looking at how to optimize the timing and make for a more robust solution, but I can say up-front that any future available throughput will be used to minimize the latency even further or strengthen the overall robustness.

    My indication to use PCMLF for the third channel was more generated towards never wasting air-time if not needed. If the third channel is a subwoofer and you can live with the low-pass filtered format we have implemented, then this will always be better than the full PCM16 format. 

    An additional question - for my application it would bee good to have the option of switching application role config - between 2.0 and 3.0 depending on the working mode - is it possible somehow programatically in the runtime ? Or the general rule is anything that is configured in PPC cannot be modified in runtime ?



    Not for a autonomous solution. You can implement this using host controlled more and have the slave choose which channels to consume with the NWM_ACH_SET_USAGE. Any channel at the master that have no consumer on the slave side will not be sent over the air and thus your will reduce the over the air BW need and thus increase the robustness. That being said, it is the master that defines the timeslot and protocol, so doing this will never be as 'efficient' as having a pure 2.0 master.

    Regards, 

    Kjetil

  • 0 in reply to Kjetil
    Intellectual 825 points

    Thanks Kjetil.

    I

    Kjetil said:
    he limiting factor is that the configurator will calculate the protocol timing for any given configuration and in case there is not room timingwise for at least one re-transmission (simplified..there are a few other things it checks as well) it will flag this either as disabling some choices in configurator or come with a warning that something is below the critical level.

    When I set up 2.1 on a Master with 48 kHz PPC does not complain but when it comes to flash programming it says it is below the critical level. But it is not a warning as it seems not to allow flash loading "at my risk". It seems that for 2.1 48kHz it only works if only 1 slave is connected. To my surprise Latency level does not impact the critical levels check.
    Is there any chance of programming 2.1 config with 48 kHz and at least 2 slaves (best would be 4) ? What PPC parameters can have impact here ? Probably changing the number of slaves in runtime is not possible ? (host-control mode)

  • 0 in reply to Pawel Piwowarski87949
    TI__Expert 3240 points

    Hi,

    unfortunately it is not possible in any way to configure a device for a 3 x PCM16 channel system with more than 1 slave. It should maybe be a more clear warning, but warning messages are displayed in the Advanced options panel e.g. under the Timeslot period setting.

    When it comes to latency, it is limited by hardware how much data that can be stored.  When using this setup, simply too much data is needed to be stored to be able to use a high latency.

    It is neither possible to change the maximum slave count during runtime.

    Best regards,
    Johan