Returns a list of CrazyRadio devices currently connected to the computer

def _find_devices(serial=None):
    """
    Returns a list of CrazyRadio devices currently connected to the computer
    """
    ret = []

    if pyusb1:
        for d in usb.core.find(idVendor=0x1915, idProduct=0x7777, find_all=1,
                               backend=pyusb_backend):
            if serial is not None and serial == d.serial_number:
                return d
            ret.append(d)
    else:
        busses = usb.busses()
        for bus in busses:
            for device in bus.devices:
                if device.idVendor == CRADIO_VID:
                    if device.idProduct == CRADIO_PID:
                        if serial == device.serial_number:
                            return device
                        ret += [device, ]

    return ret