Serial VT100 LCD problems

Hi, I'm new to Arduino so please be gentle! I have a 20x4 LCD with a serial interface which accepts vt100 codes (so great for controlling what displays where). It's here, with associated datasheets:

It has a 5 pin connector, GND, +V, RX, TX and TX(1). TX(1) is for RS232 levels, and when I patch it up to com1 on the breadboard, with putty, it works great! TX is for TTL levels, and I cannot get anything displaying !

When I put a voltmeter on Arduino TX, It seems to be permanently at around 4.8V Is Ardiuno TTL serial out inverted ? (i.e generally at VCC, with 1's at ground ? i.e. ------ for 00010010 ? ). If so, can / should I run it through an inverter ?

Hope this makes some sense to someone out there!


NewSostSerial library can use inverted logic so with that lib it is easy to test -