Android - How to find out which USB interface to use?

Question

The goal is to connect the guitar to an Android device that supports a USB host, do some signal processing and play it through the device.

The problem is that I do not find much documentation. The device can contain 6 interfaces.

However, in all the examples that I see, the first interface is always used.

UsbInterface intf = device.getInterface(0);

My device contains 6 interfaces, but the first interface, i.e. getInterface(0)has no endpoints. 3/6 do not have endpoints, and the remaining 3 have 1 endpoint.

I read that you need to find the right interface and endpoint. In my case, I want the endpoint IN to receive data.

Any advice on how that would be greatly appreciated.

Greetings

Answer 1

.

, , , .

• USB_DIR_IN (3)

• USB_ENDPOINT_XFER_ISOC (1), ,

  // Cycle through interfaces and print out endpoint info
  StringBuilder builder = new StringBuilder();
  
  for (int i=0; i<device.getInterfaceCount(); i++)
  {
      String epDirString = "No endpoints";
      String epTypeString = "No endpoints";
  
      if (device.getInterface(i).getEndpointCount() > 0)
      {
          epDirString = String.valueOf(device.getInterface(i).getEndpoint(0).getDirection());
          epTypeString = String.valueOf(device.getInterface(i).getEndpoint(0).getType());
      }
  
      builder.append("Int. " + i + " EP count: " + device.getInterface(i).getEndpointCount() + 
                     " || EP direction: " + epDirString + " || EP type: " + epTypeString + "\n");
  }
  
  // Show results in a dialog
  Builder dBuilder = new AlertDialog.Builder(USBActivity.this);       
  dBuilder.setMessage(builder.toString()).show();