|Here is the schematic from the "make_your_RS232_pod" project from|
Pierre-Philippe Coupard <firstname.lastname@example.org>
As you can see, all this circut does is invert the voltage coming from the CueCat's data line and puts the result onto the RX of the UART.
For our purpose, the fact that it operates at ttl levels is good :) Ok, to start we need to bring the UART TX & RX lines and power (gnd, vcc) out of the JuiceBox. I think using a chassis mount 4 conductor 3.5 mini audio jack will work. These connectors have 4 conductors instead of the normal 3 conductor (stereo) connectors. They are used where the stereo lines (LT, RT, GND) and the mic lines (MIC, GND) are passed thru the same connector. Neat! we can use them here!
FROM:make_your_RS232_pod.html (Pierre-Philippe Coupard)
NOTE : this serial pod only works because most modern serial ports are not too strict on the voltage levels representing a "0" or a "1" : in the definition of the RS232 standard, a "1" is coded with a voltage ranging from -3V to -12V, and a "0" is coded with a voltage ranging from +3V to +12V. Most modern serial ports will accept TTL levels as valid however, which means that they will accept 0V as a valid "1" (where they really shoudn't). Therefore, the pod's function is simply to invert the voltage coming from the CueCat's data line. If your serial port has stricter voltage level requirements, you'll have to replace the simple inverter with a specialized IC like the MAX232, to properly convert TTL to RS232.
4 conductor 3.5 mini audio jack
4 conductor 3.5 mini audio plug
I found them online for <$3 Here for the Jack and Here for the Plug