Kindle 4 Non touch serial port pinout

[geekmaster]

From #kindledev@freenode IRC channel:

yifanlu: Anyone who used the serial console on the k4 or touch give me some advice? Where's the location of TxD, RxD, GND. What chipset to use for my ttl adapter. etc Wed Jan 25 2012 - 3:57

Short answer: The K4NT unpopulated serial port connector labelled P2 is about 1 inch up from the lower-left corner of the circuit board. The solder pads from top to bottom are: GND, RxD, TxD.

Long answer:

The answer to your question was previously posted here:

https://www.mobileread.com/forums/sho...7&postcount=27

The relevant part of that post is duplicated here so that it can be found more easily:

The serial port is an unpopulated printed connector outline at the board edge, near the bottom. The GND pad at the top looks different from the others. RxD is the center pad. TxD is the bottom pad. It looks like that connector for the Touch would fit here. The pin spacing was identical to the wire spacing on an old 40-pin IDE cable. I peeled off a strip of 3 wires, and without separating them, I stripped and solder-tinned the ends, then clipped them to about 1 mm of wire showing. I added a little extra solder to the serial pads on the board, then touched the 3 wires to the pads and touched them with my hot soldering iron to bond the wires to the pads. I also used my 2-resistor and 3-diode level shifter circuit to make my usb serial adapter work with my k4nt. It allowed me to see the error message about serial number = "1" and board ID = "1" and u-boot "bailed!" because it cannot init ram on an unknown board type.

The level shifter circuit that I posted previously will let the kindle work with any usb ttl serial adapter (5v, 3.3v). You may need to remove the RxD LED from your adapter like I did, because it supplies too much current to allow the kindle TxD to pull it down to a logic zero.

You can also use usb serial cables from cell phones, with level shifting.

Some 3.3v or 5v adapters may work fine with no level shifter.

The correct way to go is to buy a real 1.8v usb serial adapter, but from places like mouser or digikey they are about $25 plus shipping. Good luck Googling "1.8v usb serial" though, because most Google hits are for 1.8m (6 ft) cables rather than 1.8v.

I got my 3.3v usb serial adapters from an ebay store for about $3 buy-it-now and free shipping, but I had to wait for them to arrive from Singapore (about 2 weeks), and I had to modify them by removing the RxD LED that exceeded with the kindle TxD current sinking ability.

[yifanlu]

I don't know why you made a new thread when I just wanted a one sentence answer from someone, which is why I asked in the IRC and not on here (it's like I texted you and you sent your reply via snail mail, if you do this for every question I ask, there will be a lot of new theeads because I ask a lot of dumb questions and don't want to flood the message boards with them <- added for clarity), but never mind that.

I did read that post you linked to a while ago and I asked because I want to make sure of the "bottom" and "top". Can you reference other components like "top below X" and "bottom above Y"?

And since we have a thread going, let's not waste the space. Anyone want to share how they connected the USB serial? Do I need an external power supply running 1.8V? Any specific adapter that works "out of the box"? I have a 3.3V USB ttl adapter that worked on the K2. The chipset supports 1.8V, but the adapter has jumpers only for 3.3V and 5V. Also, I was too cheap to buy a new soldering iron and my old one is very worn out so any way I can check if I soldered everything correctly and no shorts over the pads, I mean it boots and my multimeter doesn't show a connection on rxd->txd or txd->gnd and it got 1.8V successfully.

[seaniko7]

I used TTL-232RG-VREG1V8-WE. It worked out-of-the-box by soldering rxd cable to txd pin, txd cable to rxd pin and obviously gnd cable to gnd pin.

[geekmaster]

Originally Posted by yifanlu

I don't know why you made a new thread when I just wanted a one sentence answer from someone, which is why I asked in the IRC and not on here (it's like I texted you and you sent your reply via snail mail, if you do this for every question I ask, there will be a lot of new theeads), but never mind that.

I did read that post you linked to a while ago and I asked because I want to make sure of the "bottom" and "top". Can you reference other components like "top below X" and "bottom above Y"?

And since we have a thread going, let's not waste the space. Anyone want to share how they connected the USB serial? Do I need an external power supply running 1.8V? Any specific adapter that works "out of the box"? I have a 3.3V USB ttl adapter that worked on the K2. The chipset supports 1.8V, but the adapter has jumpers only for 3.3V and 5V. Also, I was too cheap to buy a new soldering iron and my old one is very worn out so any way I can check if I soldered everything correctly and no shorts over the pads, I mean it boots and my multimeter doesn't show a connection on rxd->txd or txd->gnd and it got 1.8V successfully.

Hmm... I thought we were done with hostile criticism of each other's posts. I guess not...

I misplaced my camera, or I would have have posted a photo just for you, with clearly labelled pins. In lieu of that, I took comments from my old buried post that already described the pins, and I created a new thread where it would be easy to find, and I added more text to be sure you would understand the pinout and the possible need for level shifting.

Then because I thought you might not actually read all of it, I added a one-line summary at the top. I even labelled the one-line sentence as "Short version".

And I went into great detail about getting 1.8v working with my super simple level shifter circuit. After I kept getting questions from my various posts, I started a new thread on that too.

I went to great lengths to try to avoid all misinterpretations and false assumptions that could be made from the short version, but ALSO explaining it at great length.

In every post about serial connections, I clearly stated that a REAL 1.8v adapter such as seaniko7 suggested is the preferred solution, but I keep getting replies that the ones from distributors cost too much (typically $25 USD plus shipping).

The one you have should work fine IF you remove its TxD LED (if it has one). If you use a 22K resistor like I did to connect the supply voltage to the level shifter circuit, it does not matter whether the supply voltage is 3.3v or 5v.

As shown in my other posts, 3.3v and 5.v TTL use exactly the same logic levels, and 1.8v TTL is different. Although many adapters need level shifting, some are more tolerant and work right out of the box.

Or, you could just do it the way I did and examine the signal at the pins. While booting, the middle pin showed a stream of pulses on the middle pin that looked like data bits, when the scope ground was connected to the metal battery cover. The top pin that looked different from the others measure zero ohms between it and the battery cover, so it was GND.

[geekmaster]

WARNING!

I just dug out my K4NT to take a photo for yifanlu. With very light pressure, I lifted the cable up for a better photo, and it snapped right off the circuit board where it was soldered. The tiny little TxD and RxD pads popped off the circuit board and are still attached to the tiny little wires! Almost no force at all!

Now I will have to find another place to attach the wires (probably at the small surface-mount resistors next to them). The ground pad is the only one still on the circuit board.

I posted this as a warning so you will be extra careful. After attaching the wires you should secure them down against the board with adhesive tape to prevent this from happening to your k4nt.

P.S. I used an temperature-controlled soldering station set to 650F, with an electrically grounded needle tip, and just a quick touch to the pads to prevent overheating. The problem is that the adhesion strength of the pads to the board is so slight that they can be easily lifted right off the board with a small lifting pressure applied to an attached cable. There are extra soldering pads give a *real* connector extra mechanical strength, but I did not use them (no connector). I soldered my cable only to the electrical pins.

Next time I would use a 5-wire cable instead of 3-wire, and I would solder the outer 2 wires to the larger P2 outer connecter pads for mechanical bonding and strength. I would also tape the cable to the board as suggested above.

[yifanlu]

Originally Posted by geekmaster

Hmm... I thought we were done with hostile criticism of each other's posts. I guess not...

I misplaced my camera, or I would have have posted a photo just for you, with clearly labelled pins. In lieu of that, I took comments from my old buried post that already described the pins, and I created a new thread where it would be easy to find, and I added more text to be sure you would understand the pinout and the possible need for level shifting.

Then because I thought you might not actually read all of it, I added a one-line summary at the top. I even labelled the one-line sentence as "Short version".

And I went into great detail about getting 1.8v working with my super simple level shifter circuit. After I kept getting questions from my various posts, I started a new thread on that too.

I went to great lengths to try to avoid all misinterpretations and false assumptions that could be made from the short version, but ALSO explaining it at great length.

You want an extremely precise description in a single sentence? Because English is an imprecise language, would you prefer that in Latin, or should I add more words to the above description and then go back and replace all my periods with commas above?

I mean, really now, do I need to write a book, just to get bashed for not injecting full understanding of the details into your brain with a single sentence?

I was really trying hard to be helpful, but you actually hurt my feelings once again, and I find it hard to be helpful when I feel as inadequate as I do after reading your replies to my posts...

In every post about serial connections, I clearly stated that a REAL 1.8v adapter such as seaniko7 suggested is the preferred solution, but I keep getting replies that the ones from distributors cost too much (typically $25 USD plus shipping).

The one you have should work fine IF you remove its TxD LED (if it has one). If you use a 22K resistor like I did to connect the supply voltage to the level shifter circuit, it does not matter whether the supply voltage is 3.3v or 5v.

As shown in my other posts, 3.3v and 5.v TTL use exactly the same logic levels, and 1.8v TTL is different. Although many adapters need level shifting, some are more tolerant and work right out of the box.

How can I be more clear on this? Help me here.

Snail mail replies? Really? I cannot text you back because you disabled PMs. WTF? And exactly HOW can I give you a one line reply that you will understand, if you did not understand the one line reply SHORT VERSION, clearly labelled and in another color, right at the top?

I think no amount of words will help because it is obvious that you are not reading my replies carefully enough. Apparently, only a photo will do, with text labels added on top in post processing with arrows and stuff.

Then why didn't you just ASK for a photo? Somebody with a camera, give this guy a PHOTO, please! And if you do not want criticism, be extremely careful how you choose your words on those labels,

Or, you could just do it the way I did and examine the signal at the pins. While booting, the middle pin showed a stream of pulses on the middle pin that looked like data bits, when the scope ground was connected to the metal battery cover. The top pin that looked different from the others measure zero ohms between it and the battery cover, so it was GND.

What is with the "not wasting space" comment? Bits are cheap. My text takes a tiny amount of space on a hard drive, and is even compressible. Onscreen, pixels are cheap -- they are reusable. The READER can skim posts or choose to not read them at all. The only thing wasted is the WRITERS TIME, especially when the intended audience does not make an effort to read it carefully and use that information to guide his own research.

Even though I was rather antisocial nerd at your age, you really have me beat on the antisocial aspect. You need grow up in that department (a LOT)... And there is that whole "respect your elders" thing... A little politeness can go a long way.

P.S. After I calm down, I will probably go back and edit this to make it more friendly, but I needed to vent my feelings first. Why do yifanlu's replies to my comments bother me so much? I got ONE good one that I cherish though (when I announce my latelst new jailbreak exploit).

Woah. Read your last paragraph. You do need to calm down. I have never made a single "hostile" post and this is the third post you made towards me that contains name calling and disrespect. All I've ever done that could be considered hostile is correct misinformation and general wrongness, and in that respect I have no bias (I'm not out to get you, I "attack" everyone equally). If I think someone is wrong, I'll correct them. They are free to rebut me and we can have a civil debate and I respect that and the person. If I'm proven wrong, I apologize. You just resort to name calling and pull the "I'm more experienced" card. And you're going on about politeness?

@seaniko7, thanks. I'll look into that.

[geekmaster]

UPDATE: I received a PM from a peer giving advice that I should not waste my time replying to yifanlu's "probably slightly disrespectul and possibly overconfident" replies to my posts.

Originally Posted by yifanlu

Woah. Read your last sentence. You do need to calm down. I have never made a single "hostile" post and this is the third post you made towards me that contains name calling and disrespect. And you're going on about politeness?

@seaniko7, thanks. I'll look into that.

Like I said, I thought we were past this petty crap. WHAT name calling? Please provide a link to each of my three posts that you claim contain "name calling" (i.e. ad hominem attacks) aimed at you. Unsubstantiated claims are worthless.

I am trying my BEST to be helpful to you, and what do I get in return from you? It sure looks like disrespect, bordering on "alpha male" hostility, to me...

Why do you divert these threads into arguments about word definitions, length of posts, and where I post them? Hostility... Criticism... Disrespect... Whatever... Regardless of how you choose to define it, your posts often criticise my posts without technical merit or references.

See #2: http://en.wiktionary.org/wiki/prima_donna

[yifanlu]

Originally Posted by geekmaster

UPDATE: I received a PM from a peer giving advice that I should not waste my time replying to yifanlu's "probably slightly disrespectul and possibly overconfident" replies to my posts. In the future such provocations by yifanlu will (hopefully) go unanswered. Hopefully...Like I said, I thought we were past this petty crap. WHAT name calling? Please provide a link to each of my three posts that you claim contain "name calling" (i.e. ad hominem attacks) aimed at you. Unsubstantiated claims are worthless. What disrespect have I shown that even APPROACHES the disrespect of your replies to my posts?

I am trying my BEST to be helpful to you, and what do I get in return from you? It sure looks like disrespect, bordering on hostility, to me...

Arguments of TECHNICAL MERIT are welcome. Please avoid petty criticism of my posts regarding their LENGTH, WHERE they were posted, WHAT words I used and how I used them, and other things that are NOT relevant to the otherwise useful technical content contained in them. You can clarify the GOOD stuff without highlighting the bad. You can, right? Can you? I can only hope...

Why do you divert these threads into arguments about word definitions? Hostility... Criticism... Disrespect... Whatever... Regardless of how you choose to define it, your posts often criticise my posts without any technical merit or references.

If you choose to argue over word definitions, you should know that I carried a dictionary around with me just about everywhere since I first learned how to read until I was older than you and I referred to it often. As a child, most of my friends were ADULTS in technical professions (i.e. mentors). I was a prolific reader and I still own many thousands of paper books (mostly technical, but a lot of Sci-Fi as well). In recent years, I went through a gauntlet of intelligence testing (including military), and I was told that my language skills are "off the charts and cannot be measured accurately". It takes MUCH more time to create content than to read it. Do you really want to waste my time like this?

My recent loss of typing accuracy is probably due to a combination of old age degradation and not enough sleep. Thankfully I can go back and clean up the spelling and grammar errors in my posts later.

I was preparing to send you my latest jailbreak package for evaluation and peer review. I am having second thoughts now...

EDIT: Regarding your claims of "name calling", there has been only ONE name that keeps popping into my head, that I really wanted to call you many times after reading your replies to my posts, but I have refrained thus far. Just for clarification, here it is: http://en.wiktionary.org/wiki/prima_donna

Again, calm down. I don't know much and I am always still learning. I know you know more than me about many things. If it makes you feel better, you are smarter and more experienced than I. However, I don't take back anything I've said, but I guess I have to physically watch what I write when you are around now because I am tired of drama every time I say something. I poke around stuff like Kindles because it's fun. It's a hobby. No need to make everything serious. I hate responding to your accusations because it'll just provoke more. If a random visitor comes into this thread and sees us two kids bickering, they can judge for themselves. I'm here to develop for Kindles not star in a Lifetime show. This is the last I'll ever speak on this subject.

[geekmaster]

Originally Posted by yifanlu

Again, calm down. I don't know much and I am always still learning. I know you know more than me about many things. If it makes you feel better, you are smarter and more experienced than I. However, I don't take back anything I've said, but I guess I have to physically watch what I write when you are around now because I am tired of drama every time I say something. I poke around stuff like Kindles because it's fun. It's a hobby. No need to make everything serious.

Once again, you answer NONE of my questions, and provide no supporting evidence for any of your prior claims against me, but instead you choose to just provoke more angst.

If you were in your shoes and I said what you just did, you would accuse me of name calling once again: http://en.wiktionary.org/wiki/drama_queen

This applies here: http://en.wiktionary.org/wiki/golden_rule

Despite that, I did tone down my post before seeing your reply. I find it interesting that you uncharacteristically preserved my ENTIRE old post in your quote (knowing that I would edit it later), instead of your usual "@geekmaster:" intro.

Regarding your "I don't take back anything I've said", the first step to recovery is admitting you have a problem.

P.S. A simple "Thank You" would have been nice.

[Lorphos]

He's right though: Don't answer irc requests by starting a new thread here.

[geekmaster]

Originally Posted by Lorphos

He's right though: Don't answer irc requests by starting a new thread here.

The K4NT serial port pin-out is not found elsewhere in the mobileread forums. There is misleading and incorrect information in the forums speculating that the serial port is located on the 4 pads near the CPU chip. My new thread was intended to provide correct information in a place that would not quickly get buried inside an existing thread, containing additional information not easily disseminated in a primitive IRC channel.

I previously documented the K4NT serial port location and pin-out (with answers to questions just asked, including the location of the serial post and its "P2" connector label), where it was apparently overlooked by those who needed this information now. This serial port pin-out is general information that could help others who do not monitor the IRC channel, and it needed to be in a prominent place like a new thread.

I try to help as many people as I can. I do not understand why anybody could have a problem with publishing the K4NT serial port pin-out in a new thread even though it was asked in the IRC channel.