Control your iRobot Create with a Palm Pilot

Step 2 Build the Null Modem

If you already have a Null Modem and a male-male 9-pin gender changer you can skip this step.

We need to use a Null Modem (as opposed to just a 9-pin gender changer) to swap the transmit-receive wires between the iRobot Create and the Palm Pilot. If we don't the transmit wire on the iRobot Create would go to the transmit wire on the Palm Pilot (that doesn't work). With the Null Modem the transmit wire on one device goes to the receive wire on the other device (and vice-versa) (this is how we want it). There are different designs for Null Modem's out there, the simplest one is the Null Modem without Handshaking. In this design the wiring is as follows:

Connecter1 | Connector2
!-------------------
Pin 2 --> Pin 3
Pin 3 --> Pin 2
Pin 5 --> Pin 5

See the pictures for a wiring diagram.

This is the most basic wiring for the Null Modem, and for our purposes it should be more then sufficient; however any Null Modem should work. Regular Null modems usually have one male end and one female end, and thus the need for a gender changer. Were using 2 male ends in this case because one end needs to plug into the Create Robot Serial Cable and the other needs to plug into the Palm Pilot's dock.

Note: I have a few extra wires in my picture because I made a Null Modem with loop back handshaking, this was a personal choice.