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NiPa_3775556
Level 2
10 replies posted 5 replies posted 5 questions asked
Level 2

Hi,

I'm currently evaluating the CYBT 343026 BT/BLE module and have a question about the PCM audio interface. In the specification for the chipset used (CYW20706 Datasheet ) in section 1.7 it indicates that the PCM interface can run in TDM mode with 1, 2, 4, 8 or 16 slots. I could not find a way to configure how many slots should be present and which slots the module should use within the WICED APIs. Have I missed something?

Thanks

Nigel

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SheetalJ
Moderator
Moderator 750 replies posted 500 likes received 500 replies posted
Moderator

WICED does not support PCM use by application directly. PCM/I2S are used internally by the BT FW for BT (SCO/A2DP) audio routing.

Even internally, PCM is used only in I2S mode.

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SheetalJ
Moderator
Moderator 750 replies posted 500 likes received 500 replies posted
Moderator

Hi nigel.paton_3775556​,

As given in the datasheet, you can select the slots depending on the rate you define.

"The number of slots is dependent on the selected interface rate (128 kHz, 512 kHz, or 1024 kHz). The corresponding number of slots for these interface rate is 1, 2, 4, 8, and 16, respectively."

For more details, check the file /20706-A2_Bluetooth/include/wiced_hal_pcm.h.

You can get API information from API Reference: WICED Studio 6.2.1 (CYW20706).

NiPa_3775556
Level 2
10 replies posted 5 replies posted 5 questions asked
Level 2

Hi,

It mentions 3 clock rates but 5 different number of slots (I note the header file has 5 clock rates). When configured to use the PCM interface on a headset profile, pairing with a phone and then making a call, I can see the bit clock is 512kHz for 16bit 16kHz WBS audio using 2 slots. Also there does not appear to be any API with which to set the clock rate.

How do you tell it which slots to use? If it is configured for 4 slots how do you tell it to use slots 2 and 3. For example if there are two of these modules on the same PCM interface you'd want one to use slots 0 and 1 for example and the other to use 2 and 3. Or if you have a simple device like a digital microphone that may have no control over the slots it uses e.g. it will just us the first slot after the frame starts and therefore all other devices on the interface need to use other slots.

Thanks

Nigel

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SheetalJ
Moderator
Moderator 750 replies posted 500 likes received 500 replies posted
Moderator

WICED does not support PCM use by application directly. PCM/I2S are used internally by the BT FW for BT (SCO/A2DP) audio routing.

Even internally, PCM is used only in I2S mode.

NiPa_3775556
Level 2
10 replies posted 5 replies posted 5 questions asked
Level 2

Okay, thanks for the information.

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