Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > General > Decrypting

Reply
 
Thread Tools Search this Thread Display Modes
Old 1st February 2018, 07:16   #1  |  Link
Rupan
Registered User
 
Join Date: Nov 2008
Posts: 62
Serial settings for the newer LG drives

Many (all?) of the newer LG drives - those based on the Mediatek ARM SoC, not the Renesas drives - appear to have 3.3v (CMOS logic) serial headers on the back, next to the SATA/power connectors. Based on a quick look with an oscilloscope, it seems that the ramp down/up for one bit is somewhere between 113 ~ 120 kilohertz, so I'd guess that the serial line speed is 115200. However, when I connect a USB<->Serial device I get garbage in minicom. Does anyone on this forum know the correct settings?
Rupan is offline   Reply With Quote
Old 1st February 2018, 08:56   #2  |  Link
jpsdr
Registered User
 
Join Date: Oct 2002
Location: France
Posts: 1,702
You can first try to play with the several standards settings for an RS232 port COMs :
Parity bit : None, Odd, even
Stop Bits : 1,2
This will make 6 settings to test.
I doubt you'll have to test for 7 bits data...
But, do you know what you're supposed to receive and/or send ?
It's not because it's a serial link that you're supposed to receive text.
There is often serial link on devices for testing/maintenance purpose, which send (or receive) pure binary data/information.

Last edited by jpsdr; 1st February 2018 at 08:59.
jpsdr is offline   Reply With Quote
Old 3rd February 2018, 16:30   #3  |  Link
Mike Chen
Registered User
 
Join Date: Jun 2008
Posts: 70
These are correct settings. MTK firmware does not log strings, instead it uses a custom binary log format with message IDs and arguments encoded as binary. Useless without formware source code. What exactly you wanted to see there?
Mike Chen is offline   Reply With Quote
Old 4th February 2018, 05:20   #4  |  Link
Rupan
Registered User
 
Join Date: Nov 2008
Posts: 62
I was hoping that there was some way to upgrade, downgrade, or patch areas of the firmware via the serial console. Maybe implement some sort of rudimentary GDB backend, if possible. Would you be willing to share what you know of the binary protocol (if anything)? Can you confirm the remainder of settings for the serial interface, including data bits, stop bits, parity, and flow control?
Rupan is offline   Reply With Quote
Old 5th February 2018, 09:07   #5  |  Link
jpsdr
Registered User
 
Join Date: Oct 2002
Location: France
Posts: 1,702
The most usual is 1 bit stop, no parity, 8 bits data. But it's just the most usual, no garanty for sure it's what is used here.
jpsdr is offline   Reply With Quote
Old 5th February 2018, 20:24   #6  |  Link
Rupan
Registered User
 
Join Date: Nov 2008
Posts: 62
Indeed, the 8n1 serial configuration seems to be in widespread use. I don't remember ever using a serial device with settings other than those. However, this is a highly specialized device which is probably hostile to unauthorized users and it wouldn't surprise me if some parameters were nonstandard. The problem is that since the protocol is binary I have no way of telling whether the data I see is garbage as a result of say 2 stop bits instead of the usual 1 stop bit.
Rupan is offline   Reply With Quote
Old 5th February 2018, 21:00   #7  |  Link
Mike Chen
Registered User
 
Join Date: Jun 2008
Posts: 70
Quote:
Originally Posted by Rupan View Post
I was hoping that there was some way to upgrade, downgrade, or patch areas of the firmware via the serial console.
No, none of it is possible via UART. But all you ask is actually possible via other means. For example all firmware versions (including the latest one, with disabled vendor commands and ATA extension to access SPI flash) do allow reading the same debug data from the ring buffer using vendor commands.

Quote:
Originally Posted by Rupan View Post
Would you be willing to share what you know of the binary protocol (if anything)?
I never cared enough to actually fully decode it, but trust me - it is useless for most part.

Quote:
Originally Posted by Rupan View Post
Can you confirm the remainder of settings for the serial interface, including data bits, stop bits, parity, and flow control?
I do not know . If you really want I can decode the initial handshake bytes from your firmware, so you can check if you are getting the right data. There is however one useful thing you can do with the serial header - I'm not ready to discuss it publicily yet, but if interested - please PM me or better write to mike@makemkv.com .
Mike Chen is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 00:10.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.