Commands are working fine with USB- Serial cable and HDMI responding to the laptop when i am sending command with terminal. But when i connected my HDMI with serial to serial cable(NULL MODEM CABLE) it again stop responding. Cable is fine because i am using same cable with Projector to send command and projector is working fine.So please suggest me weather i have to change to other type of cable or install any software or how can i resolve this issue now.Please suggest me if null modem cable is not working then how can i communicate with HDMI.