Implementing a class-compliant USB MIDI device

RE: Implementing a class-compliant USB MIDI device

Edvin — Fri, 05 Jul 2019 11:29:35 GMT

Hello Gaétan,

Please check why nrf_drv_usbd_ep-enable_check(ep) returns what it does. It should be in nrf_usbd.h (you may need to copy it out to the app_usbd.c file in order to debug it).

Please create a new ticket where you describe your progress and your issue. I'll be out of office for a couple of weeks, so this ticket is not looked after.

RE: Implementing a class-compliant USB MIDI device

Gaétan — Fri, 05 Jul 2019 06:42:58 GMT

Hello,

I am also working on a MIDI over USB version for the nRF52840.
I have adapted the declarations and the USB enumeration works correctly. The host software recognizes my card as a MIDI device.

However, I have a problem with sending and receiving data....
Obviously the endpoints I use are not enabled for the NRF!

For example, when I try to send via the app_usbd_ep_handled_transfer function, it returns NRF_ERROR_INVALID_STATE to me because of the nrf_drv_usbd_ep_enable_check(ep) test (line 1835 of app_usbd.c)

I think there is a concern about the init of part of the USB communication...
I noticed that I only have one call to the setup_event_handler() function with setup.bmRequestType = 128, whereas if I understand the principle correctly there should be several calls to initialize the endponits.

If needed I can send an example of my code.

Regards,

Gaétan

RE: Implementing a class-compliant USB MIDI device

Andrew Mowry — Mon, 17 Jun 2019 19:26:23 GMT

I would love to see an example of USB MIDI if anyone has it working. Using a single chip for both Bluetooth MIDI and USB MIDI would be very useful.

RE: Implementing a class-compliant USB MIDI device

Edvin — Tue, 05 Feb 2019 07:35:11 GMT

Hello,

Please create a new ticket where you describe your progress and issues with the MIDI implementation.

BR,

Edvin

RE: Implementing a class-compliant USB MIDI device

tim11 — Fri, 01 Feb 2019 09:36:09 GMT

Hi Edvin,

Yes, tried to change it to midi streaming, but cant at at the moment work out how to fix the corresponding descriptions.

RE: Implementing a class-compliant USB MIDI device

Edvin — Tue, 29 Jan 2019 14:53:29 GMT

Hello Tim,

I am sorry, I haven't looked much into the USB MIDI since I last answered on this thread. Did you try to change the implementation to MIDI? Maybe Beul made some progress?

RE: Implementing a class-compliant USB MIDI device

tim11 — Mon, 28 Jan 2019 21:04:41 GMT

Hi,

Can you possibly give any more advice on getting usb midi to work. I'm stumped by it.

Thanks

Tim

RE: Implementing a class-compliant USB MIDI device

Edvin — Tue, 18 Sep 2018 13:35:46 GMT

Hello,

Sorry for the late reply. I spoke to one of the guys who worked with the USB implementation on the nRF52840. He says that they didn't have time to implement a midi-example, but everything needed should be there to set it up.

But, as I mentioned, we don't have an example doing this.

I suggest that you start by testing the USBD audio example, as described here.

Then look for the APP_USBD_AUDIO_GLOBAL_DEF() for the microphone in main.c.

APP_USBD_AUDIO_GLOBAL_DEF(m_app_audio_microphone,
MIC_INTERFACES_CONFIG(),
mic_audio_user_ev_handler,
&mic_form_desc,
&mic_inp_desc,
&mic_out_desc,
&mic_fea_desc,
0,
APP_USBD_AUDIO_AS_IFACE_FORMAT_PCM,
192,
APP_USBD_AUDIO_SUBCLASS_AUDIOSTREAMING
);

You would at least want to change this to be a midi.

change:

APP_USBD_AUDIO_SUBCLASS_AUDIOSTREAMING to APP_USBD_AUDIO_SUBCLASS_MIDISTREAMING

then you need to change all the mic_defines to MIDI defines. Exactly which one, I am not sure. You will have to read up on how MIDI over USB works.

Best regards,

Edvin