topic Re: Run Speaker With USB 2.0 Stack in Kinetis Microcontrollers

Run Speaker With USB 2.0 Stack

aniketmarkande — Thu, 16 Nov 2017 10:00:25 GMT

Hi,

I am working on SDK2.0 USB stack forK22 series micro-controllers.

My aim is to read .mp3 files from mass storage device and play it on speakers, so want the information.

I know that audio files are sent over Isochronous transfer type and i am using USB_HostAudioStreamSend() function send audio data. So the question is do i have to create timer of 125us and call USB_HostAudioStreamSend() function again to send complete data or callback function is called after 125us?

if i am missing something please let me know. Just want to know how implement in my code.

Regards

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Tue, 21 Nov 2017 12:21:47 GMT

Kindly somebody reply. Its urgent.

Thank you.

Re: Run Speaker With USB 2.0 Stack

jingpan — Tue, 28 Nov 2017 06:15:30 GMT

Hi aniketmarkande,

Sorry for reply you so late. Yes, I think you have to use a timer to control the transmition speed. Because there is no software timer to ensure that one ISO transfer is sent per one SOF timer without the hardware PIT timer enablement, the issue also is effected by the KHCI hardware SOF Threshold feature. The host may sends less/more audio data to the device after a while. As a result, the buffer on the device side experiences an underrun/overrrun error. If the device doesn’t have an appropriate method to deal with it, some noise will occur.
Btw, the K22 USBOTG only support full speed. The inturrupt interval is 1ms.

Regards

Jing

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Tue, 28 Nov 2017 06:23:10 GMT

Hi Jing Pan,

Thank you for your response.

But do you have any example code to read from audio file and run speaker.

I tried 1 Ms timer but when I read from in isr execution gets stucked there.

Any solution for this?

Regards,

Aniket

Re: Run Speaker With USB 2.0 Stack

jingpan — Tue, 28 Nov 2017 08:08:02 GMT

Hi,

I can't find such a example. Maybe this link can give you some ideal: usb audio generator

Regards

Jing

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Tue, 28 Nov 2017 10:42:56 GMT

Hi Jin Pan,

Thank you for your support. With 1ms timer i was able to play the sound.

only problem is it does not sound as it should be, its too noisy. :smileysad:

any workaround for that? or any way to get SOF interrupt anyhow?

Regards,

Aniket

Re: Run Speaker With USB 2.0 Stack

jingpan — Wed, 29 Nov 2017 07:00:13 GMT

Hi,

you can get the sample rate in g_pFormatTypeDesc->tsamfreq[][]. This value is got from device. It indicates which samplerate does the device support. Some usb speaker only support fixed samplerate. Then you have to adjust your PCM samplerate.

Regards

Jing

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Thu, 30 Nov 2017 09:49:17 GMT

Hi Jing Pan,

i am trying to play the .wav file and sampling frequency in the .wav file is 32khz and also g_pFormatTypeDesc->tsamfreq[][] is also showing 32khz.

do we have to convert the audio data from .wav file, since it has data in 2's compliment format for 16 bit PCM encoding?

i am sending 192 bytes(g_audio.maxPacketSize) every 1ms.

Also is noise is related to SOF, since i am sending at every 1ms timer interrupt and not after the SOF?

Thank you.

Regards,

Aniket

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Thu, 30 Nov 2017 11:16:35 GMT

Hi Jing Pan,

One more doubt, when .wav file is read it has signed data and function used to send the stream data "USB_HostAudioStreamSend()" typecast the data bufer to unsigned.

although if i change the argument to int8, the chain of function to send data over usb also typecasts data buffer always to unsigned.

this might be causing the noise? any solution for this?

Thank you.

Regards,

Aniket

Re: Run Speaker With USB 2.0 Stack

jingpan — Thu, 14 Dec 2017 02:01:11 GMT

Hi aniketmarkande,

Wave file is signed data. But USB stack dont care data format. So don't worry about it. I think your problem is on bitrate. I think you may adjust sample number in each packet. If the samplerate is 32000 and you send data each 1ms, you should only put 32000/1000=32 samples in a packet.

Regards

Jing

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Fri, 15 Dec 2017 09:18:40 GMT

Hi Jing Pan,

Thank you for your response. :smileyhappy:

32 samples per seconds i tried sending, its plays too slow. Since wav file has PCM 16 bit data, i am sending 64 bytes every 1 ms and plays without noise(pattern of the tone is correct). But the audio does not sound exactly as it sounds on pc, sounds little harsh. It will be great help if you can share some information how to do solve this problem. (sorry i am not able to explain exactly whats the problem)

Also i am using USB interrupt for sending to send every 1ms. (i hope this is correct).

I tried 1 ms timer but it does not play well as sound chip plays data on when it received SOF.

Waiting for your response.

Regards,

Aniket

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Wed, 20 Dec 2017 21:10:45 GMT

Please help out, running out of time.

Thank you

Re: Run Speaker With USB 2.0 Stack

jingpan — Thu, 21 Dec 2017 02:24:16 GMT

Hi,

Since you are host, can you read back the usb speaker's information?

Regards

Jing

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Thu, 21 Dec 2017 12:39:40 GMT

Hi Jing Pan,

If you tell me exactly what information, i will provide you here. I see that i get that speaker supports 32Khz, mono channel in audio structures.

Also in function USB_AudioTask(), when case "kRunAudioSetCurSamplingFreq" is executed and Audio_ControlCallback is called, status is not "kStatus_USB_Success", getting "kStatus_USB_TransferStall". Other switch cases are successful.

Is that might be the problem?

What is the reason for kStatus_USB_TransferStall and how to resolve it. DAC chip used is PCM2706C.

Regards,

Aniket

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Thu, 28 Dec 2017 10:41:17 GMT

reply asap. thank you

Re: Run Speaker With USB 2.0 Stack

jingpan — Fri, 29 Dec 2017 05:45:08 GMT

Hi,

It seems that this the clock asynchronous problem. There is not much good way to deal with this problem. Please review the link https://community.nxp.com/thread/379414?commentID=607907#comment-607907. There is much discuss in it and it's link page.

When you excute case: kRunAudioSetCurSamplingFreq, there is an item you must take care: sync type. This is the information of what the synchronous type of the usb speaker. Then base on this value, you can adjust your feed strategy. Detail please find in the link.

Regards

Jing

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Tue, 02 Jan 2018 08:22:24 GMT

Hi,

DAC chip PCM2706C uses Adaptive sync mode and my feed strategy is that i am sending 64 bytes every 1ms since my wav file is 32khz sampled with 16 bit PCM encoded data.

For 1ms i am using USB interrupt only.

Anything wrong with this strategy?

Thanks & Regards,

Aniket

Re: Run Speaker With USB 2.0 Stack

jingpan — Tue, 02 Jan 2018 10:13:11 GMT

Hi,

Adaptive mode is: Recover clock based on data rate and adjust the clock just as synchronous method. This work should be done by usb device, not host. You may not get any feedback from device.

I'm not familiar with PCM3706. But since K65 works as a host, PCM2706 should try to fit your speed. If you config it properly, the sound should be ok. Have post your question to TI?

Regards

Jing

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Tue, 02 Jan 2018 10:22:26 GMT

Thank you :smileyhappy:

I will post to TI about the issue.

Regards,

Aniket

Re: Run Speaker With USB 2.0 Stack

aniketmarkande — Tue, 02 Jan 2018 10:24:14 GMT

Hi,

Also is it correct to use USB interrupt for 1ms reference?

Regards,

Aniket