code: def write(self, size=None):
          
          if size is None:
              self._drv.set_data(self.tobytes())
          else:
              self._drv.set_data(self.tobytes()[:size])
  
          if "auto_start" in self._conf:
              if self._conf["auto_start"]:
                  self._drv.start()
docs: to call start() automatically, set yaml file as follows:
          registers:
            - name        : CCPD_PCB
              type        : StdRegister
              hw_driver   : CCPD_PCB_SPI
              size        : 32
              auto_start  : True  <------ add this
              fields: ......