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Old 12-24-2011, 10:23 AM   #2
geekmaster
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Posts: 6,433
Karma: 10764860
Join Date: Nov 2011
Location: Multiverse 6627A
Device: K1 to PW3
You can get external foldable keyboards for PDA pocket computers that use serial I/O on ebay for about $5 to $10. Do not get a keyboard that uses BlueTooth.

The kindle 3 has the serial I/O jack available at the lower slot in the left edge, and there are instructions on this forum how to make a connector and cable for it. Because the keyboard does not supply power, you can get power from the upper slot in the left side, but the bottom connector mus be adapted to short the bottom two pins in the lower slot to turn on battery power to the upper slot.

Other kindle models have the serial connector inside and require opening your kindle to access the serial port. There are kindle opening instructions for the different model in this forum and elsewhere as well. You might be able to locate a source of battery power inside the kindle as well, but this requires some level of electronics expertise. You could also connect an external power source (batteries or power supply).

Depending on what model keyboard you have, it may be necessary to buy or build a level-shifter circuit to convert between different TTL voltage levels. This can be done with two resistors and 3 diodes (or less). You can build something fancier with transistors, or you can buy a ready-made level shifter IC or circuit.

You also need software to configure you kindles serial port to use the same speed as your keyboard. Some keyboards need 9600 bps.

Unfortunately, this is an software and electronics hacking job. But hey, if you feel up to it, go for it. I bought some of these keyboards to use with my kindles. I will write whatever software I need WHEN I get around to that project (currently rather low priority). I will post my results back to this forum when that happens.

Good luck with that!

Last edited by geekmaster; 12-26-2011 at 12:24 AM.
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