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Original question:

LP-CC2652RB: PDM Stream Example from Audio Plugin

CC2652RB: PDM Stream Example

Manoj S
Prodigy 20 points

Part Number: CC2652RB

Hi,

PDM to PCM conversion, TI Team I referred  to the audio plugin example (pdmstream).

In that Example I need some clarity about the input clock frequency that can be set.

We are using  ICS-41352 PDM output sensor, there we have 3 power modes as described below.

I wanted to know whether can I use the Ultrasonic Mode by using the input CLK frequency as (4.1 - 4.8 MHz) instead of 1.024 MHz(mentioned in the example).

Thank you,
Manoj

  • 0
    TI__Guru** 101490 points

    Hi Manoj,

    On CC13xx/CC26xx devices (including CC2652RB devices), the PDM driver is implemented on the top of the I2S module. In other words, the PDM driver configures the I2S driver to sample the data and execute the proper decimation filters.

    On CC26xx/CC13xx devices, the I2S driver is tested SCK frequency between 47 kHz and 4 MHz. So it won't totally fit the use case you are targeting.
    Additionally, the decimation filter (i.e. the SW filter used to convert PDM data in PCM data) only supports 1.024 MHz inputs. The frequency response of the filter for higher frequencies may not be that good and the filter may have to be tuned a bit.

    If you want to run some tests, you may want to modify the I2S clock divider configuration within the file PDMCC26XX_util.c - the following line is probably the one to twiddle.

    object->audioClkCfg.bclkDiv = 47;

    If you want to modify the decimation, you'll have to look into the assembly code for the compiler you are using (see in <SDK>\source\ti\drivers\pdm).

    I hope this will help,

  • 0 in reply to Clément
    Prodigy 20 points

    Hi,

    On CC13xx/CC26xx devices is there any driver which we can use to fit the use case of Ultrasonic range(input clk is > 4.1MHz) for sound frequencies(PDM to PCM conversion).

    If yes can you please let me know.

    Thank you,

    Manoj S

  • 0 in reply to Manoj S
    TI__Guru** 101490 points

    Hi,

    Manoj S said:
    On CC13xx/CC26xx devices is there any driver which we can use to fit the use case of Ultrasonic range(input clk is > 4.1MHz) for sound frequencies(PDM to PCM conversion).

    Nothing I can think of.

    As I mentioned before, you may want to use an external codec.

    Best regards,