README 

This test program continuously sends "Note On" and "Note Off" MIDI events to an
attached USB MIDI tone generator, which can be connected and removed from the
system (USB plug-and-play). After (re-)connect the tone sequence starts again.


USB GADGET MODE

This test program works on the Raspberry Pi (3)A(+), Zero (2) (W) and 4B in USB
gadget mode too. These models allow to connect the on-board DW USB controller
directly to an USB host for USB gadget (aka device) operation. The Raspberry Pi
4B uses the USB-C power connector for that purpose. You need a suitable USB
cable. The Raspberry Pi is normally bus-powered via the USB host in any case for
this test. A separate power supply need not be connected.

If you want to self-power your Raspberry Pi, you have to ensure that the supply
voltages at the USB connector and the power connector are exactly the same.
Otherwise there is a risk of damage. Be careful!

A configuration is required for this test. First you have to enable the define
USB_GADGET_MODE in the file kernel.cpp. Furthermore you have to define the macro
USB_GADGET_VENDOR_ID with your USB Vendor ID to be used for the USB device. See
the file include/circle/sysconfig.h for details!
