Communication with projector Epson via RS232

[espen.sorensen@jmhansen.no]

Hi,
I've got a LM5p2-PMC.
I want to control a Epson projector via the RS232-port. The projector has the proprietary protocol ESC/VP21.
My goals are to switch the projector on/off, control the volume and switch between the HDMI sources.
The commands are to be sent from buttons on a Zennio Z41 display. So, I've to bind it up to a event script.

I've no lua-programming experience, so I'm grateful for any tips or examples?

Explaining of ESC/VP21 protocol:

ESC/VP21 Command List
When the power ON command is transmitted to the projector, the power
turns on and it enters warm-up mode. When the projector's power has turned
on, a colon ":" (3Ah) is returned.
When a command is input, the projector executes the command and returns a
":", and then accepts the next command.
If the command being processed terminates abnormally, an error message is
output and a ":" is returned.
The following commands are available.

Item Command
Power On/Off 
On PWR ON
Off PWR OFF

Signal selection Computer1 Auto SOURCE 1F
RGB SOURCE 11
Component SOURCE 14
Computer2 Auto SOURCE 2F
RGB SOURCE 21
Component SOURCE 24
HDMI1 SOURCE 30
HDMI2 SOURCE A0
USB SOURCE 52
LAN SOURCE 53
Screen Mirroring * SOURCE 56
HDBaseT ** SOURCE 80
A/V Mute On/Off On MUTE ON
Off MUTE OFF

Serial connection
• Connector shape: D-Sub 9-pin (male)
• Projector input port name: RS-232C
• Cable type: Crossover (null modem) cable

Communications protocol
• Default baud rate setting: 9600 bps
• Data length: 8 bit
• Parity: None
• Stop-bit: 1 bit
• Flow control: None

[admin]

Here's a short example without confirmation from the projector. Replace /dev/ttyUSB0 with /dev/RS232 if using built-in RS-232 port.
https://forum.logicmachine.net/showthread.php?tid=129