I can not find service port pinouts and voltage levels for Philips tv sets on serv-u & serv-c connectors(used at least on model 32pf5331/12). Probably on others also. Those connectors are for "service use only".
EDIT: Also if someone happens to have a service manual and/or firmware for Philips 32pf5331/12, I would appreciate to find those.
It's a simple standard uart interface. Firmware is on support.philips.com