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The USB standard defines two types of ports: Host and Device. You cannot connect a Device to another Device. There must be a Host to support a Device. PCs act as Host. The Axim is a Device. You cannot connect the Axim to anything but a PC through USB.
To get around that limitation for external communications, Dell came out with a so-called Serial cable that converts the USB Device signals to RS232 Serial signals. However, the Dell cable was specifically designed to connect to a PC RS232 port that puts power on a certain Serial interface pin. That power on that pin then activates the signal conversion process in the Dell cable.
So, PC-Mobile then reverse engineered the Dell cable to create a serial cable (or engineered their own) to connect to GPS units. they replaced the standard RS232 connector with GPS-specific connectors and did the wire-swapping needed to communicate properly. Basically, the PC-Mobile cable replaces the Null Modem and etrex serial cable that would be required if all you had was the Dell cable.
Ok, all of that was to lead to this statement: Forget USB. You cannot communicate with the etrex using USB in any way. The PC-Mobile cable converts USB to Serial so your problem is entirely Serial. Read the boards here for how to trigger the Serial communications successfully.
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