topic Re: Bare Metal USB Stack - USB_Class_Audio_Send_Data not ready in Kinetis Microcontrollers

Bare Metal USB Stack - USB_Class_Audio_Send_Data not ready

deek — Wed, 17 Sep 2014 21:51:30 GMT

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?

Re: Bare Metal USB Stack - USB_Class_Audio_Send_Data not ready

Kan_Li — Thu, 18 Sep 2014 06:41:16 GMT

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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Re: Bare Metal USB Stack - USB_Class_Audio_Send_Data not ready

deek — Fri, 19 Sep 2014 18:24:55 GMT

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...

Re: Bare Metal USB Stack - USB_Class_Audio_Send_Data not ready

Kan_Li — Wed, 24 Sep 2014 02:12:56 GMT

Hi Deek,

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

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
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