Palm USB cradle - MOD to support both USB and Serial!

Started by jharris1993, Nov 07, 2010, 08:39

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I have a Palm m130 that I inherited after my sister-in-law discovered the USB cradle would not work on her Vista machine.

I have discovered:
With a serial cable and a serial-to-USB adapter, (available almost everywhere, dirt cheap), you can use the Palm device on Windows Vista and Windows 7; though you may have to go to Prolific's web-site to download drivers.  After some judicious searching, I was able to download drivers for this adapter that work on Win-7 64 bit!

The only problem with this is that you have to have the Palm device in the cradle to keep it charged.

Yet in order to hot-sync you have to first remove it from the cradle, connect it to your serial cable and then initiate the hot-sync manually via the hot-sync app on the Palm as many serial cables do NOT have a hot-sync button.

Then you need to remember to disconnect the serial cable and return it to the cradle to keep it from discharging on you.  It's a pain, and it has discouraged me from using an otherwise excellent Palm PDA.

I undertook to discover if there was a way to make the USB cradle also work for Serial connections.  This way I could have the convenience of being able to leave it in the cradle and yet still be able to take advantage of the serial connection to sync it.

After disassembling the cradle (4 very small Torx screws on the bottom feet), I discovered that the "universal connector" is mounted on a small PCB that - on one side of the universal connector - there are solder points for the USB cable to connect.  On the opposite side of the connector, there are *unused* solder-points where a serial cable can be added.

Then there are three things that need to be done:
1.  Attach a DB-9 (female) connector to the cradle via a fairly long multi-conductor cable, (at least six wires plus shield), via a small hole drilled in the back of the cradle right near the existing cable opening.

(See the pin-out located at for instructions on how to wire it.)

2.  Add a small switch, (or two pins and a jumper block), to the back/bottom of the cradle, and wire the switch / two pins to the "ID1" solder-pad on the USB side of the PCB and ground.

3. *Carefully* remove the small "resistor" located just above the hot-sync switch - between the switch and the Universal Connector.  This enables the switch/jumper connected between ID1 and ground to control the cradle's "mode".

With the switch closed / pins shorted, the Palm device is in USB mode, and expects a working USB connection.
With the switch open / jumper removed, the Palm device switches to Serial mode, and will hot-sync using a serial connection, or a serial-to-USB adapter.

The beauty of this is that it allows you to use a serial connection to hot-sync the Palm device, yet have it in the cradle where it can stay charged.  If at some later point USB drivers become available, (*don't* hold your breath waiting!), or you move to a computer that supports Palm's drivers, you can throw the switch / add the jumper and go back to USB mode.

Took me several days of experimenting, chasing pin-outs with an ohmmeter and cursing the TINY LITTLE CONNECTOR PINS on the Universal Adapter to finally get this beast working.  I now have the best of both worlds.

What say ye?



hmmm a recent edit date of Nov 7, 10. Well, I just installed Palm Desktop version 6.2.2 and hot synced my m125 first. no problems. took a few seconds to detect and load drivers (I watched the hard drive LED). then I hot synced my TX and no problems. This is the first time syncing the m125 and I've had the TX for several years and had version 4.something of Palm Desktop installed but had somehow lost the USB sync option.
BTW I running Vista.



Are you running 32 bit or 64 bit?  The USB workarounds work well on 32 bit operating systems, but puke on the 64 bit systems - which is what I have.  Since Prolific has 64 bit drivers for my "Dynex" USB-Serial Adapter (from Best Buy), I was able to install and do serial hot-syncs.  With the USB cradle mod, I was able to have the best of both worlds.