if not buf:

                    logAllDmx.debug('%s: empty buf- no output', self.shortId())

                    return

                # ok to truncate the last channels if they just went

                # to 0? No it is not. DMX receivers don't add implicit

                # zeros there.

                buf = buf[:self.lastDmxChannel]

                if logAllDmx.isEnabledFor(logging.DEBUG):

                    # for testing fps, smooth fades, etc

                    logAllDmx.debug('%s: %s...' % (self.shortId(), ' '.join(map(str, buf[:32]))))

                sent = self.dev.send_multi_value(1, bytearray(buf))

                if sent != len(buf):

                    raise ValueError("incomplete send")

            except ValueError:

                self.reconnect()

                raise

            except usb.core.USBError as e:

                # not in main thread

                if e.errno == 75:

                    metrics('write_overflow', output=self.shortId()).inc()

                    return

                msg = 'usb: sending %s bytes to %r; error %r' % (len(buf), self.uri, e)

                log.warn(msg)

                if e.errno == 13:  # permissions

                    return self.crash()

                if e.errno == 19:  # no such dev; usb hw restarted

                    self.reconnect()

                    return

                raise

'''

# the code used in 2018 and before

class UdmxOld(BackgroundLoopOutput):

    def __init__(self, uri, bus):

        from light9.io.udmx import Udmx

        self._dev = Udmx(bus)

        super().__init__(uri)