If you can use the serial interface, works like a champ, use the codes below as is
.

PANASONIC PLASMA RS 232 CODES FOR RTI


With power off, this plasma display will only respond to the PON command.


Power On= \x02PON\x03
Power Off= \x02POF\x03
Volume = \x02AVL:**\x03 Where ** is Enter-Value between 00 and 63
Audio Mute Off= \x02AMT:0\x03
Audio Mute On= \x02AMT:1\x03



Input Select Toggle= \x02IIS\x03
AV Mode= \x02IIS:VID\x03
Component/RGB Mode= \x02IIS:YP1\x03
{Processed as a Y/Pb/Pr or RGB Signal as set by this unit}
PC Mode= \x02IIS:RG1\x03


{Screen Mode}

Normal= \x02DAM:NORM\x03
Zoom= \x02DAM:ZOOM\x03
Full= \x02DAM:FULL\x03
Just= \x02DAM:JUST\x03
Auto= \x02DAM:SELF\x03



Baud Rate= 9600 BPS
NO Parity
Char length= 8Bits
Stop bit = 1Bit