Help with unbricking kindle via serial port

[yifanlu]

Ok, I screwed up bad and bricked my Kindle 2. I was messing with the Kindle system files, trying to get ubuntu to boot, and I know I messed up something in /etc/init.d and the kindle won't boot up anymore. I know it can still turn on by measuring the voltage of various ports, and I know exactly what file I screwed up to brick it. Now the only problem is fixing it. I'm tried to build an TTL to RS232 adapter, but it wouldn't work. I tried to order one from eBay, but that I think the adapter was DOA. Now, I have some questions before I purchase another adapter. Hopefully someone with experiences with the serial port can answer.

1) If you purchased a working RS232 adapter for the kindle, please send me a link.
2) What is the voltage? I measured GND -> VCC on the kindle and got 2.8V. But adapters are either 3V, 5V, or 5.5V. Which one should I buy?
3) Do I need an external power supply (battery)? I see a lot of people doing this. Why (doesn't VCC provide power)? If so, what type of power supply and what voltage? Where do I connect the power supply if it's needed?
4) Is this right? With the kindle facing down, battery towards the bottom, the order of the pads (left to right) is: VCC, Tx, Rx, GND
5) What's the PuTTY settings?

Sorry for the stupid questions, but I need to be 100% sure before I try again. I don't want to screw up farther and burn the serial port or something. I tried searching, and all threads dealing with serial port aren't detailed enough for me. Thanks.

[Sir Alex]

1. I have used self made adapter with FT232RL chip.
2. Kindle port is 1.8V.
3. No, you can find 1.8V next to RX,TX,GND pads
4. Sorry don't remeber pads order...
5. You must use HyperTerminal 115000 8N1 wit No flow control, but HyperTerminal and settings depend on adapter you will use.

[yifanlu]

Originally Posted by Sir Alex

1. I have used self made adapter with FT232RL chip.
2. Kindle port is 1.8V.
3. No, you can find 1.8V next to RX,TX,GND pads
4. Sorry don't remeber pads order...
5. You must use HyperTerminal 115000 8N1 wit No flow control, but HyperTerminal and settings depend on adapter you will use.

Thank you for the reply. Is the 1.8V the VCC pad (there are 4 pads)? If I use a 5V TTL to RS232 adapter, can I safely connect the kindle to it?

[troyme]

a usb to ttl adapter is much better .the link I bought from
http://item.taobao.com/item.htm?id=4911508078

worked ok and need nothing more
I had debricked my dx once from delete kernel modules

[Sir Alex]

@yifanlu

If you use 5V TTL adapter you can damage your Kindle port, because it is 1.8V!

[yifanlu]

Originally Posted by troyme

a usb to ttl adapter is much better .the link I bought from
http://item.taobao.com/item.htm?id=4911508078

worked ok and need nothing more
I had debricked my dx once from delete kernel modules

Thank you, I'll look into that. Do I just connect Vcc->vcc pad, gnd->gnd pad, or do I need an external power source?

[troyme]

with the adapter on above link
Just connect GND->GND, TX->TX, RX->RX
No Vcc connection needed,
3 foot connection is enough.
No external power need.Nothing more

[Siliverst]

I would have used a homemade adapter on a chip FT232RL as advised by Sir Alex.
1.8V internal voltage from the Kindle is connected to pin 4 (VCCIO) FT232RL.
When using 5V TTL, you may damage the serial port of the Kindle.
Datasheet for FT232RL - http://easyelectronics.ru/datasheet/FT232RL_V202.pdf
scheme of the adaprer similar to this one: http://dorkbotpdx.org/blog/feurig/a_...gramming_board
But you need to connect to the device only: GND, TXD, RXD, and 1.8V (to Pin 4 FT232RL) from Kindle.
You can use any external voltage 1.8V, connected to GND & VCCIO of the FT232RL.

[yifanlu]

Thanks for the help guys. I'll try out these methods.

[RaedwulfHolt]

yifanlu, which method worked best for you?

[h1uke]

Originally Posted by Siliverst

1.8V internal voltage from the Kindle is connected to pin 4 (VCCIO) FT232RL.
When using 5V TTL, you may damage the serial port of the Kindle.

you mistakenly imply the K3 model. I pretty believe that the K2 which yifanlu has
uses 5V logic.

[axsdenied]

I have been following these forums for a while so I might as well post something useful in my 1st post :-)
For the record, I have built similar converters for various devices in the past (not for the Kindle but there are all more-or-less the same ).

First of all the important stuff to prevent you from killing your Kindle :

• You said that you measured VCC=2.8V on the Kindle. This would imply that you need 2.8V instead of 1.8V on the RX and TX lines. Everybody else is talking about 1.8V... are you sure you have 2.8V?
  What is the voltage on the RX and TX lines (relative to GND)?
  Which Kindle model?
• If you connect the VCC lines between the Kindle and the serial converter, make sure you don't connect 1.8V from the Kindle to 5V on the FTDI chip. This will definitely kill the Kindle. Only connect the power lines if they have the same voltage (or use resistors - not in this case).

So, assuming that you need 1.8V:

• You need an USB to RS232 converter that gives serial lines at 1.8V (for example they come in 1.8V, 2.8V, 3.3V, 5V). If you use the wrong voltage, you may kill your Kindle.
• If you can find one in the shops, great. They will most likely use an FTDI chip. You don't need the power line from the Kindle (VCC) to the FTDI chip. The FTDI module (USB to serial converter) will draw power from the USB port while Kindle will power itself from its battery.
  You need only RX, TX and GND. Again, make sure it is the 1.8V version.
• If you are building one using the mentioned FTDI chip (FT232R series for example) make sure that you connect the 1.8V from the Kindle (VCC) to the VCCIO line on the FTDI chip - this will give you 1.8V RS232.
• You have to cross over the RX and TX lines between Kindle and FTDI chip, i.e. RX <-> TX and TX <-> RX.

Also:

• Measure all voltages before you connect things together.
• To test your old DOA module or before you connect the self-built module to the Kindle, connect the RX and TX lines together. This will echo anything you send from a terminal program (I use wxterm on the Windows). If you get nothing back, the module is not working.

[yifanlu]

Originally Posted by axsdenied

I have been following these forums for a while so I might as well post something useful in my 1st post :-)
For the record, I have built similar converters for various devices in the past (not for the Kindle but there are all more-or-less the same ).

First of all the important stuff to prevent you from killing your Kindle :

• You said that you measured VCC=2.8V on the Kindle. This would imply that you need 2.8V instead of 1.8V on the RX and TX lines. Everybody else is talking about 1.8V... are you sure you have 2.8V?
  What is the voltage on the RX and TX lines (relative to GND)?
  Which Kindle model?
• If you connect the VCC lines between the Kindle and the serial converter, make sure you don't connect 1.8V from the Kindle to 5V on the FTDI chip. This will definitely kill the Kindle. Only connect the power lines if they have the same voltage (or use resistors - not in this case).

So, assuming that you need 1.8V:

• You need an USB to RS232 converter that gives serial lines at 1.8V (for example they come in 1.8V, 2.8V, 3.3V, 5V). If you use the wrong voltage, you may kill your Kindle.
• If you can find one in the shops, great. They will most likely use an FTDI chip. You don't need the power line from the Kindle (VCC) to the FTDI chip. The FTDI module (USB to serial converter) will draw power from the USB port while Kindle will power itself from its battery.
  You need only RX, TX and GND. Again, make sure it is the 1.8V version.
• If you are building one using the mentioned FTDI chip (FT232R series for example) make sure that you connect the 1.8V from the Kindle (VCC) to the VCCIO line on the FTDI chip - this will give you 1.8V RS232.
• You have to cross over the RX and TX lines between Kindle and FTDI chip, i.e. RX <-> TX and TX <-> RX.

Also:

• Measure all voltages before you connect things together.
• To test your old DOA module or before you connect the self-built module to the Kindle, connect the RX and TX lines together. This will echo anything you send from a terminal program (I use wxterm on the Windows). If you get nothing back, the module is not working.

Thanks for the info. I was wrong about the 2.8V. I don't know how I got that, but measuring the port right when it's turning on gives me 1.8V.