The logic levels for the ccTalk line are 3.5 to 5V for mark state (idle ) and 0 to 1V for space state (active). This allows a low cost interface width 5V microcontrollers. Some dedicated gaming PC based platforms like this one have one or more built in ccTalk ports.
A normal switching diode can be used but the noise margin could be to low. The resistor can be in 1Kohm to 10Kohm range. If the Tx output is open colector you can connect together TX RX and data line without the diode. also the resistor is not required if the slave has a pull up.
You can skip the diode if the microcontroller has internal protection diode.
I know that the levels are not exactly by the book , the input low level for Pic microcontrollers is guaranteed at 0.15 VDD for CMOS inputs. 1V means 0.3VDD for 3.3 V and 0.2VDD for 5V but this worked for me flawlessly
For PC there are many USB to RS232 TTL adapters available that can be used with the schematics above , search Google, they have 5V and 3.3V outputs. If you want a ready made ccTalk cable Alberici has one (pl2303 based) or you can find some more in “Usefull ccTalk links” page.
There is also on youtube a video where this guy is simply connecting TX and RX and data together , I doubt that the TX output is open collector the slave just force zero the output that acts also as a pull up when idle. This might reset your USB to serial chip if the output is stronger.
Of course do not forget the official schematics from the ccTalk documentation , I don’t have their agreement to show them here but you can find them in ccTalk documentation part 3 page 82 to 85.