Quote: Originally Posted by pippolippi
Not that I understand romanian, but it seems this folk connected directly the changer to a pc rs232 port and saw this: 3D 01 FE FD 3D 01 FE FD 3D 01 FE FD.
Well, directly seems a bit risky to me, but it could work.
The official RS232 standard states, if I'm not mistaken, that positive level must be between 5 and 15 and negative between -5 and -15 for emission, and accepted with positive between 3 and 25 and negative between -3 and -25 for reception devices.
So normally, any voltage received between -3 and +3 volt falls into the "unspecified" range and should be avoided.
This being said, many PCs place their threshold at a positive voltage (e.g. 2.5V), so that devices that cannot produce negative voltage can be received too.
Some PCs (notably laptop) even *send* 0V for "negative", to avoid the hassle of a voltage pump to provide the negative voltage (the main goal of the MAX232).
So with a divider, I easily believe the MAX232 is not really needed on input, but seeing its price, I prefer to keep it and be on the safe side - theoretically at least :-)