So I have a small keyboard that was made as an external keyboard

USB is a complicated business, and the PDA is old, so it likely doesnt speak USB. much more likely it's proprietary, or it could be PS2, tho it requires an extra line for a clock.

File: ipaq_12p.jpg (191KB, 1024x889px) Image search: [Google]

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>>1080741
>>1080729
It's not USB. I used to have one of those HP Ipaqs. They're USB slave only. They can be connected to a PC through USB but you can't connect keyboards, mice,etc to them through USB.

The cradle connector also had an RS232 port which must be what your keyboard goes through. You should be able to connect it to the RPI through it's UART. I'm pretty sure it was full 12v RS232, so you'll need a MAX232 chip and a few capacitors to level shift to TTL RS232.

File: FKDGBTJIQV7OUGW.LARGE.jpg (58KB, 1024x576px) Image search: [Google]

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>>1080741
This is the connection, it has a single data line. The one I have doesn't have those components, it instead has two melf diodes.

>>1080752
Oh, good, I was hoping uart or i2c was an option. I wouldn't think I'd need 12v, tho, the keyboard itself is like 3v or something

>>1080756
The RS232 output is probably using 12V=0 0v=1 since that's the standard. It doesn't matter that the device runs at 3V; RS232 ports have hardware to switch up the voltage. A RPI's UART can only LVTTL-RS232. That's where 3.3V=0 0v=1. You need a MAX232 chip to do the level conversion.

>>1080795
Ah.

Honestly I'm wondering if I should simply remove everything above the ribbon cable and matrix it myself.
It looks like everything's feeding into a em78p447sam controller so I don't really know if i wanna fuck with that that much. What do y'all think?

>>1080987
There should be an RS232 level shifter on the keyboard. Connect to the input of that and you'll get a signal that can go directly to the rpi UART.

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>>1080729
Iirc the iPAQ used a serial protocol for the keyboard. The USB connection happened in the cradle itself, not in the iPAQ. Try using one of those knockoff saleae analyzers from china like pic related. You should be able to see enough to decode the keyboard output.

I've got some version of pic related, and it works fine under sigrok


Look for in logic analyzer. Should be $10 or less.