Unbriking Kindle DX

[knc1]

The post at:
http://www.mobileread.com/forums/sho...d.php?t=170566

Contains links to both the datasheet on the cable your using and to the datasheet on the chip which is molded into the cable.

It is fairly programmable, I would not be surprised to find that it has a loopback test mode that could be useful here.

[cavorite]

FTDI quite generously makes available a Factory Test Utility http://www.ftdichip.com/Support/Docu...%20utility.pdf, but it needs a specially wired cable and a second serial port. Given the 1.8v output, I'd need at least a level converter, if not another (functional) FTDI 1.8v TTL to USB cable. If I have one of those then testing becomes a moot point.

At this point, the basic hardware loopback will be enough to determine if I need to order a new cable. At least that's a better alternative than if the DX serial port is broken.

[knc1]

Too save the soldering / un-soldering to the DX connection pads . . .
You might want to cut the adapter cable back aways from the DX and insert a 3-circuit audio jack/plug in-line.
Sort-of a poor mans "quick dis-connect" device.

[cavorite]

I used a three pin fan connector when I did the original wiring. Ground in the center, just in case I needed to exchange RX and TX.
Resoldering on PCBs is best avoided. Lifted pads are not fun.

[geekmaster]

Originally Posted by cavorite

I used a three pin fan connector when I did the original wiring. Ground in the center, just in case I needed to exchange RX and TX.
Resoldering on PCBs is best avoided. Lifted pads are not fun.

I usually do connector layout so that you can safely short any two adjacent pins together (whenever possible). Just personal preference after a lifetime of electronics hobby and work experience. In this case, I would do "GND-RxD-TxD". Another benefit (for SIP pin headers) is that you can use a jumper to test RxD (loopback).

But then you need to know which side is GND, of course.

[cavorite]

I usually do connector layout so that you can safely short any two adjacent pins together (whenever possible).

Excellent safety idea. I guess it depends on your audience. For end users, idiot proof and safety over flexibility. For test/design users, flexibility and ease of modification, but safety not too far behind. I am reminded of the old TV "cheater" cords.

Since I was designing for myself and one-time use (hopefully), I scrounged instead of ordered. This should have been a quick, trivial affair (sigh).

[knc1]

Originally Posted by cavorite

Since I was designing for myself and one-time use (hopefully), I scrounged instead of ordered. This should have been a quick, trivial affair (sigh).

It IS a quick, trivial affair;

Once lab126 publishes the technical reference manual to their DX and DXG design.

Until then, I will keep right on typing up a table of the hardware memory address map, drawn from the published source code. (While trying to ignore the code typo's in the source.)
Just hang in there, I'm typing as fast as an old man can look things up.

Credit where credit is due: With a bit of help from GCC's (usually turned off) abilities to generate various interesting listings and cross-references.

[knc1]

It may be that your DX is responding to software flow control (ctrl-s, ctrl-q).

Perhaps it choked on a stray ctrl-s (might have been passed by the terminal setting up the USB device's UART) ;
Try giving it a ctrl-q

[cavorite]

Well - I'll try that soon as the new usb-serial cable comes in. The simple loopback test failed, and hopefully that was the sole guilty party.

Ever wonder if lab126 has an occasional look here? Hope we provide some amusement...

[knc1]

Originally Posted by cavorite

Well - I'll try that soon as the new usb-serial cable comes in. The simple loopback test failed, and hopefully that was the sole guilty party.

Ever wonder if lab126 has an occasional look here? Hope we provide some amusement...

Gremlins?

Do you save things?
Even broken things?

I would keep that "bad" cable for its four programmable control leads.
Who knows? You might someday have something CMOS that needs its reset button pushed remotely via USB.

[cavorite]

Oh definitely. I can't bring myself to toss out stuff like this without proof it's completely dead, but neither am I going to take the time to exhaustively test it for every possible use. I collect old radios and test equipment to fix them, and saving parts is a habit.

[knc1]

Don't give up on this recovery project.
I am still looking things up, it is just taking a bit longer than I had expected.

[twobob]

Good advice for life really.

[cavorite]

Waiting on my replacement USB/serial adapter, then ready for guinea pig duty...

[knc1]

Two little notes:

That: "press any key to stop autoboot: " prompt . . .

You can press the key at any time prior to the prompt, you don't have to wait to be prompted.
(The uart receive buffer is not flushed prior to the prompt.)

The: "Does the battery charge while sitting in u-boot?" question.
Ans: Yes.
It is noted as a special lab126 addition to u-boot, the charger current limit is set to the 500ma limit while in u-boot.

I can imagine why . . .
It lets the lab126 developer go home at the end of the day with the Kindle sitting at the u-boot command prompt and not finding the battery dead when returning to work the next morning.