[WaseemAlkurdi]

Originally Posted by Yorker

I have something i got some time back, it's a red board with 5 pins sticking out and no jumper, so i guess i need to solder RX TX GND?

This is the guide i found
https://www.mobileread.com/forums/sh...90&postcount=1
I only have the adapter no serial cable, i'm assuming if i connect the adapter to a usb port and solder the pins to the kindle board it should work but what bothers me is the voltage you mentioned since my board doesn't have a jumper just pins, here is a link

https://www.ebay.com/itm/New-USB-2-0...0AAOSwUBJdEMK6

This is the one indeed, except that it doesn't have the jumper, as you noted. You only need to connect three pins:
1. Board Rx to Kindle Tx
2. Board Tx to Kindle Rx
3. Board Ground to Kindle Ground (or to a bare cable squeezed under a screw on the Kindle board).

Note that ground is NOT optional - there will be no serial output until you connect it.

To make sure that the adapter is the right voltage, connect one terminal of your multimeter to the Tx pin of the board and the other to the board's ground. If the board gives out 1.8 - 3.3 volts, you're good to go. Otherwise, buy a new one with a jumper, or solder resistors and electronic magic until the voltage goes down to 1.8 or 3.3 volts. Late Geekmaster has left us the schematic for such a "logic level shifter circuit if you have to build one.

Edit: Looking at the product description, you do have both 5 V and 3.3 V, but they are on separate pins, where Tx is 3.3 volts. Doesn't hurt to check it with the multimeter though.
And your adapter is different because it's based on a different chip, the CP2102. But people have reported success with this adapter too. Search this forum if it doesn't work out of the box (but it should).