code: def to_string(self):
          
          # From ykdef.h :
          #
          # // Frame structure
  	# #define SLOT_DATA_SIZE  64
          # typedef struct {
          #     unsigned char payload[SLOT_DATA_SIZE];
          #     unsigned char slot;
          #     unsigned short crc;
          #     unsigned char filler[3];
          # } YKFRAME;
          filler = b''
          return struct.pack('<64sBH3s',
                             self.payload, self.command, self.crc, filler)
docs: Return the frame as a 70 byte string.