LPC55xx USB audio without speaker

[TwoBias]

Hello NXP community,

for a project i use the LPC5528 SDK example code for USB composite audio+hid device.

I modify the code to fit with the customer requirements and replace the audio codec. It works fine and approval is on the way.

For an other device there is no speaker implementation needed. Also it is not a functional problem if the operating system install a speakerdriver but the hardware has no speaker connector, it confuses the customer.

So i try to change the SDK example to remove the speaker but unfortunately without success. My idea is to modify only the USB descriptor according to other example codes (USB audio generator ,USB speaker only) and leave the audio code unchanged and instead deactivate the playback in codec register config.

I tryed with these and some other defines:

#define USB_DEVICE_CONFIG_AUDIO (2U)

#define USB_DEVICE_INTERFACE_COUNT (4)

#define USB_AUDIO_SPEAKER_STREAM_ENDPOINT_COUNT (2)

#define USB_COMPOSITE_INTERFACE_COUNT (4)

But all my experiments ended up with a driver error an yellow marked sign in pc device manager.

Do you think it is possible to reduce the composite SDK example to microphone+hid device that way or do i have to rewrite the complete code handling in the controller to get it working?

Do you have any idea or solution to push me forward?

Thanks

[xiangjun_rong]

Hi, Tobias,

As you know that the USB is only a channels to transfer data between host(PC) and device(the USB of LPC55xx functions as device), it is okay you use audio class as speaker, but do not have the codec on the device, in this way, the PC transfer a fixed number of data to the device in a fixed interval, but the device does not use the data.

Hope it can help you

BR

XiangJun Rong

[TwoBias]

Hello Rong,

thank you for your reply.

Yes, you are right. At the moment i did it the way you described.

It works but the pc operating system shows a speaker ready to use although my device has no speaker.

Do you know a solution how to modify the code/defines that the device (LPC55) is only (microphone audio class + HID) instead of (microphone+speaker audio class + HID)?

best regards

TwoBias

[xiangjun_rong]

Hi,

I think you can modify the descriptor of speaker, for example decrease the interface number in configuration descriptor, remove the interface descriptor of speaker, and corresponding END descriptor of speaker, remove the speaker specific descriptor. Furthermore, delete the code of USB speaker.

Hope it can help you

BR

XiangJun Rong

[TwoBias]

Thank you for the idea.

Yes,I think this is the right way to go, too.

I will go further with this.