The following is a translation in English of the original document that can be found at:

The Greek Palm Site

It was originally written in Greek by Michalis Papamichail and translated in English by Stefanos Dris.

Modifying the m50x USB Cradle to Include a Serial Connection

Figure 1  

Palm has used the same PCB in the USB cradle and the serial cradle (figure 1). As can be seen, the connectors for the USB cable are on the left, while those intended for the serial cable are on the right. The PC differentiates between the two connections (USB or serial) using an smd resistor that is exactly above the hotsync button (see figure 2).

Figure 2

The USB connection utilizes zero resistance, while the serial one requires a resistance of 7.5 kW. The following table shows how the solder pads on the PCB need to be connected to the serial cable. Caution: The resistor has to have a 1% tolerance.

After connecting the solder pads on the PCB to the serial cable, the PC needs to be able to use it. This is achieved by exchanging the zero-value resistor that is above the hotsync button (figure 2), with the 7.5 kW resistor mentioned above. The effect of this is that the PC will ALWAYS connect to the Palm serially. In order to be able to use the cradle with the USB connection too, a simple on-off switch can be placed on the outside of the cradle. Its sole purpose is to short the two sides of the newly installed resistor so that a zero resistance is detected when the hotsync button is pressed. Hence, the cradle can be switched from USB to serial and back (figure 3).

Figure 3

Figure 4 shows what the inside of the cradle will look like after soldering the serial cable wires:

Figure 4