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Full Version: Hardware hack to use the gotype palm keyboard on the zaurus
OESF Portables Forum > Everything Else > Archived Forums > Distros, Development, and Model Specific Forums > Model Specific Forums > Sharp Zaurus > 5x00 Hardware
Trying to figure out a way to make a hardware hack to use the gotype palm keyboard on the zaurus. I'm thinking that because there is a serial connector on the go type that maybe I could use an rs32 to serial converter and make a custom driver. What do you guys think.
This shouldn't be too difficult, but Landware won't make it as easy as it could be: they turned me down when I asked them for protocol info last year. So a little reverse engineering will be required.

To connect to the keyboard, there's "The Bridge" family of widgets available from Since I have a couple of similar projects in mind, I've emailed them to ask whether they'll sell the PCB and shell separately, so it isn't necessary to unsolder the PDA connector part(s) as soon as you buy it.

You shouldn't need a full RS-232 conversion: inverted TTL will almost certainly suffice. But the keyboard probably works by stealing power from one of the RS-232 lines, so using a CMOS buffer chip probably won't work because they don't source enough current. If I were doing this (and I probably will, to get a Palm Stowaway running), I'd start with an LM358 op amp as a driver receiver (you should only need to drive the handshaking line for power, and convert the serial data in from the keyboard). If it also wants to use the serial data out (I think the Stowaway might use it for a "wake-up line), use an LM324. It's easier to build than a MAX232 circuit and, if it doesn't work, about the worst that can happen is that you blow up a 25-cent chip.

I heard back from Midwest PCB: they're willing to sell the PCB and shell for $2 apiece. It'd be a little tacky-looking, and might be difficult to come up with a good strain relief, but it means you could have a connector to plug into most Palm III accesories for $4 (or Palm V, if you prefer: they'll sell the parts to that connector for the same price). If you have a zThincable, or one of Five Star Associates' serial cables, you could probably just wire a DB-9 to that connector, do a little tweaking of the IRK driver, and be ready to type.

There's a chance it wouldn't be quite that simple, because the keyboard might not get enough current from the cable's RS-232 driver to work. But it's worth a try, and you can always fall back to making an interface for the Z end if you have problems.

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