Category: Projects Related to Palm OS PDAs

Charge and Sync with a USB-only-Dockingstation

Published on: 2021-05-06

Caution: I won’t take any responsibility for any damage!


If you own some Palm devices, you might be familiar with this picture:

Okay, your chargers and docking stations are not such a mess, but you will probably have a few chargers and docking stations. Since Palm devices from Palm were the most popular Palms, I guess that this is one of the most common docking stations:

The dock was available with a USB or serial cable. The one shown here is a docking station with a USB cable and a dedicated charger.

At the time when Palms with the Palm Universal Connector were released, such as the Tungsten T, T2, T3, C, W, Zire 71, m500, m505, m515, i705, m125, or m130 (also the Garmin iQue 3600 and 3200 used this connector), USB 2.0 was the standard USB connector. Since USB 2.0 is limited to 500mA, a dedicated charger with more current was needed to charge the devices properly.

The charger that came with this docking station is an original charger from Palm and outputs 1A at 5V, 5W in total:

Currently, USB 3.0 or even USB 3.1 is the "new USB 2.0" and a lot of computers have USB 3.0 ports. But how much current can USB 3.0 provide? A look at the Wikipedia article about USB 3.0 tells us: 900mA. Not exactly 1A, but I would guess that Palm calculated some headroom in their chargers. So maybe it is possible to get rid of the charger and charge the device with the USB cable only.

So I opened the docking station and cut the wires from the charging port.

The thin red (+) and black (-) cables are the ones from the USB port, in this case: "U3" and "U4":

So I soldered the cables, which were attached to the charging port, to "U3" and "U4". A bit of heat shrink tubing should prevent shorts, since it is a bit tight there after all:

After putting everything back together, here was the test. This is an unmodified docking station, only the USB connector is connected to a USB charger. It does not charge:

But with the modified docking station, the Tungsten C is charging:

Success so far. And on a USB 3.0 port, it draws nearly 750mA. Which is more than the allowed 500mA for the USB 2.0 port, but less than the 900mA which USB 3.0 can provide.

Since the Tungsten C has internally two batteries, a Palm m515, with only one battery, draws even less current: only around 470mA. Which could theoretically be handled by USB 2.0, but practically, you don't want to work so close to the limit.

And since it is still USB, a Hotsync is of course also possible:

So, with this modification, you could theoretically get rid of all your chargers for Palm devices with the Palm Universal Connector. ;-)