You were absolutely right. Mine works in key mode and serial mode. Nevertheless, the seller assured me this was serial-control mode only. Now makes sense for me SOMO14 dual functionality. I can confirm that V 1.5 could work both ways. Not pretty sure about previous versions of this audio module. Tested play, pin 9 to ground, and next, pin 13 to ground. Both worked out just fine. Did try this mode the first time, but since my first sd card was not working, never tried it again. Thanks to you to make me back to test this mode.