[HARDWARE] UART Cable time

[happytomato]

I've been reverse engineering the bootloader for the G955F in an attempt to find some sort of exploit to let us root our devices and not trip the KNOX flag. It now seems like the next step is to get in to the bootloader UART.

I've looked at guides such as: https://forum.xda-developers.com/showthread.php?t=1901376 where they make a microUSB version of this cable and have attempted to replicate this with the USB-C connector by shorting the CC pins to ground with various resistances but have had no joy.

Looking at the kernel source, I can see this:

"-MHL:1K",
"-VZW Accessory:28.7K",
"-VZW Incompatible:34K",
"+RDU TA:40.2K",
"+HMT:49.9K",
"-Audiodock:64.9K",
"-USB LANHUB:80.07K",
"-Charging Cable:102K",
"+Game Pad:121K",
"+TYPE1 Charger:200K",
"+Jig USB Off:255K",
"+Jig USB On:301K",
"+Deskdock:365K",
"+TYPE2 Charger:442K",
"+Jig UART Off:523K",
"+Jig UART On:619K",
"+TA:eek:PEN",
"+USB:eek:PEN",
"+CDP:eek:PEN",
"+Undefined Charging:XXX";

Which definitely indicates that the known resistor values should work, but so far, I can not get any serial output at all. Is my assumption that USB-C cables actually have CC wires, rather than an internal resistor in the connector head correct?


UPDATE: I have attached the pinout for the UART cable.

 

[jujusito]

Getting it would be amazing.

 

[halo87]

I believe This will take time

 

[Tkkg1994]

@Vatsal can you please move this to the right place?
As this forum place here is not how-to/guides/questions.

Thanks very much as always :good:

 

[Vatsal]

@Vatsal can you please move this to the right place?
As this forum place here is not how-to/guides/questions.

Thanks very much as always :good:

Thread moved Sir.
Next time, kindly use the report button.

Thanks:good:

 

[nosympathy]

This post, posts of my own, and others I've seen SCREAM that we need a Dev Discussion section like XDA used to have (least majority of the phones I had 3-4 years ago plus had them.) Would be dev discussion only where the OP is actually working on a dev issue (root, getting dex to run sans dock, etc.) and be able to get actual help.

Unfortunately these dev type threads get buried by non dev like questions and I imagine the people capable of helping won't come in here and dig for stuff to help with.

 

[happytomato]

This post, posts of my own, and others I've seen SCREAM that we need a Dev Discussion section like XDA used to have (least majority of the phones I had 3-4 years ago plus had them.) Would be dev discussion only where the OP is actually working on a dev issue (root, getting dex to run sans dock, etc.) and be able to get actual help.

Unfortunately these dev type threads get buried by non dev like questions and I imagine the people capable of helping won't come in here and dig for stuff to help with.

+1

I would really like to get this working but could really do with some outside input. Having this in the more general section is going to make this vanish quickly.

 

[happytomato]

look what I got

@jujusito @halo87 @nosympathy @dragunbayne @Harry44

Look what I just got in the mail...

...now just to reverse engineer it and make a schematic.

 

[halo87]

@[email protected]@[email protected]@Harry44

Look what I just got in the mail...

...now just to reverse engineer it and make a schematic.

How would would this take?

 

[happytomato]

@halo87 That sentence didn't make much sense...

 

[haksancan]

You should ask this kind of questions on a proper EE forums because I don't think you'll have useful answers here. We're just a bunch of clueless dudes poking with firmware files.

 

[t-shock]

Excited to see that someone is working (sort of) on exploiting the bootloader and thus avoiding the knox counter

Please let us know with your future progress :good:

 

[militiaOfDeath]

@jujusito @halo87 @nosympathy @dragunbayne @Harry44

Look what I just got in the mail...

...now just to reverse engineer it and make a schematic.

Any progress on this? Trying to achieve UART myself, but so far nothing.

 

[happytomato]

Any progress on this? Trying to achieve UART myself, but so far nothing.

I actually made one and then lost it when formatting my laptop. I shall probably do it again in the next few days, possibly today. Heads up though, it is not a solution in itself. The resistor magic happens within the Anyway Jig and I think that only the S103 is compatible with USB C. In any case, watch this space. If you want to share any findings, please PM me!

 

[TimelessPWN]

I've been reverse engineering the bootloader for the G955F in an attempt to find some sort of exploit to let us root our devices and not trip the KNOX flag. It now seems like the next step is to get in to the bootloader UART.

I've looked at guides such as: https://forum.xda-developers.com/showthread.php?t=1901376 where they make a microUSB version of this cable and have attempted to replicate this with the USB-C connector by shorting the CC pins to ground with various resistances but have had no joy.

Looking at the kernel source, I can see this:


Which definitely indicates that the known resistor values should work, but so far, I can not get any serial output at all. Is my assumption that USB-C cables actually have CC wires, rather than an internal resistor in the connector head correct?

How were you going about reverse engineering the bootloader

 

[vermiciouskanid666]

Is my assumption that USB-C cables actually have CC wires, rather than an internal resistor in the connector head correct?

Doesn't usb-c spec call for a 56k resistor in the cable? I remember there being a problem with incorrectly manufactured cable having 10k resistors.

 

[happytomato]

How were you going about reverse engineering the bootloader

I am using IDA Pro. I wish I also had hex-rays, but that is a little out of my budget.

 

[happytomato]

Doesn't usb-c spec call for a 56k resistor in the cable? I remember there being a problem with incorrectly manufactured cable having 10k resistors.

I think so, but I am not 100% clear on the USB C spec. I can confirm that there are no resistors at all inside the cable though.

 

[happytomato]

The pinout has now been uploaded. Happy hunting.

By the way, if anyone has an Anyway box and fancies sending it to me, I would be deeply grateful. Progress is getting slowed by how expensive it is to get hold of all of these secret Samsung parts.

 

[Diablosss]

someone succed to make uart cable ?