def trace_start(self):
        """Starts collecting trace data.

        Args:
          self (JLink): the ``JLink`` instance.

        Returns:
          ``None``
        """
        cmd = enums.JLinkTraceCommand.START
        res = self._dll.JLINKARM_TRACE_Control(cmd, 0)
        if (res == 1):
            raise errors.JLinkException('Failed to start trace.')
        return None