Bare Metal USB Stack - USB_Class_Audio_Send_Data not ready

[deek]

I’m implementing a KL25 USB device based on the following example:

Freescale_BM_USB_Stack_v5.0\Src\example\device\audio\generator

The example waits for enumeration, then calls USB_Class_Audio_Send_Data() in a loop.  This appears to work fine unless the stack is not ready for the next packet (this depends on the host latency).  I cannot find a callback or a method to poll that tells me it is safe to call USB_Class_Audio_Send_Data().  I think I can poll the OWN bit in the BDT, is there an easier way?

[Kan_Li]

Hi Deek,

I am sorry, but I dont understand "This appears to work fine unless the stack is not ready for the next packet (this depends on the host latency). " would you please explain your concern in details? Thanks for your patience!

Have a great day,
Kan

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[deek]

Kan,

Thanks for the reply.  My question is the proper usage of USB_Class_Audio_Send_Data().  Does this call block until the data is sent, or do I need to wait for a notification that I can send more data?  If I need to wait for a notification, is that USB_DEV_EVENT_SEND_COMPLETE or something else? The USB_Stack_Device_Reference_Manual.pdf is not clear.

Regards...

[Kan_Li · Accepted solution]

Hi Deek,

For the Audio send/receive, there are two conditions needs before they can be called.

1. ISO transfer has an interval parameter, so APP needs to make sure the internal between two send/receive is called match the ISO transfer interval
2. The second call needs to wait the previous call is done, that’s  USB_DEV_EVENT_SEND_COMPLETE.

Hope that helps,

Have a great day,
Kan

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