def recv_messages( self ):

        # read updated write-pointer
        widx = self.ddr_widx.value
        assert widx < self.NUM_MSGS  # sanity-check

        if widx == self.ridx:
            return  # nothing to do


        txdata = ''

        # process batch of messages

        # note: it may be faster to copy a batch of messages from shared memory
        # instead of directly accessing individual messages and their fields.
        while self.ridx != widx:
            msg = self.msgbuf[ self.ridx ]

            # sanity-check that message id increments monotonically
            # (i.e. no messages from pru got dropped)
            dropped = ( msg.id - self.lastid - 1 ) & 0xffffffff
            if dropped != 0:
                raise RuntimeError( f'{dropped} messages dropped by PRU (0x{self.lastid:08x} -> 0x{msg.id:08x})' )
            self.lastid = msg.id

            # get 32-bit timestamp (in cycles) from message and unwrap it:
            self.timestamp_cycles += ( msg.timestamp - self.timestamp_cycles ) & 0xfffffff

            position = msg.position
            angle = self._Count_to_angle( position )
            force_adj = self._Force_correction( angle )
            force = msg.force - force_adj

            txmsg = [ self.timestamp_cycles, force, angle ]
            txdata += map( str, txmsg ).join(',') + '\n'
            # or just:  txdata += f'{self.timestamp_cycles},{force},{angle}\n'

            # consume message and update read pointer
            self.ridx += 1
            if (self.ridx == self.NUM_MSGS):
                self.ridx = 0
            del msg
            self.shmem.ridx = self.ridx  # direct access to message forbidden beyond this point


        # send data to client
        self.writer.write( txdata.encode('ascii') )

        # TODO maybe bail out with an error if too much data buffered in the writer?
        # you can check with writer.get_write_buffer_size()


        # update user interface
        timestamp_ms = self.timestamp_cycles // 200000
        timestamp_s = ( timestamp_ms % 60000 ) / 1000
        timestamp_m = timestamp_ms // 60000
        timestamp_h = timestamp_m // 60
        timestamp_m = timestamp_m % 60
        timestamp_label = f'{timestamp_h:02d}:{timestamp_m:02d}:{timestamp_s:06.3f}'
        print( f'\ridx=0x{self.ridx:04x} id=0x{self.lastid:08x} time={timestamp_label} angle={angle} force={force:08d}', end='\x1b[K', flush=True )