Not sure if USB2Serial Light from Arduino or a FTDI cable would work any better/easier as they seem to convert USB TXD & RXD into a 5v TTL level and I need to interface to a true rs2s2 +/1 12v TXD & RXD.
That's even easier, get a USB2RS232 adapter, the ones with a Prolific PL2303 are only a few bucks.
p.e. http://www.amazon.com/RS232-SERIAL-Adapter-CABLE-PL2303/dp/B00404N0IQ
I am using a standard configuration connection to the arduino with a Max 3222 IC but when it is connected to the arduino, the RXD line seems to be loaded down so that no signal is seen on it. When I remove the part, (or even just lift the pin of the part) this line toggles like it should when I am typing characters into my keyboard while connected to hyper terminal.
The MAX 3222 doesn't generate a +/- 12V signal but a +/- 5V signal (according to the datasheet) but this should be OK for most applications.
The MAX 3222 doesn't have an RXD pin. How did you connect the Arduino to this chip?