docs: def _serial_send(self, port, payload):
          '''
          Send data to connected device.
  
          Parameters
          ----------
          port : str
              Device name/port.
          payload : bytes
              Payload to send to device.
          '''
          if port not in self.open_devices:
              # Not connected to device.
              logger.error('Error sending data: `%s` not connected', port)
              self._publish_status(port)
          else:
              try:
                  device = self.open_devices[port]
                  device.write(payload)
                  logger.debug('Sent data to `%s`', port)
              except Exception as exception:
                  logger.error('Error sending data to `%s`: %s', port, exception)