[Q] Building a serial UART cable for I9300 / which voltage

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reinsn

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Jan 6, 2013
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I'm trying to build an UART/USB-Cable for my I9300

I found conflicting information about the voltage. Some sorces say to use an converter with 3,3V others 5V. Can anybody tell me what's correct?

Any additional links to information about UART/Serial console/which USB Controller in I9300 would be greatly appreciated. Useful information is very rare on this topic.
 
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bahtsiz_bedevi

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Dec 12, 2011
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I'm trying to build an UART/USB-Cable for my I9300

I found conflicting information about the voltage. Some sorces say to use an converter with 3,3V others 5V. Can anybody tell me what's correct?

Any additional links to information about UART/Serial console/which USB Controller in I9300 would be greatly appreciated. Useful information is very rare on this topic.
Why don't you use something like this? http://www.ebay.com/itm/FT232-USB-U...488?pt=LH_DefaultDomain_0&hash=item3a7b2522d8
FTDI even has an android app for its products https://play.google.com/store/apps/details?id=com.ftdi.j2xx.hyperterm
It worked fine on Galaxy S2.
 
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bahtsiz_bedevi

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Dec 12, 2011
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This is what i want to use, but it supports TTL levels 3,3 and 5V. Which are you using for your SGS2?
I'm assuming it was 3.3V. I used it for flashing a bootloader of a router using a computer. But it worked on Android too, no custom kernel was required.

---------- Post added at 12:40 AM ---------- Previous post was at 12:38 AM ----------

This is what i want to use, but it supports TTL levels 3,3 and 5V. Which are you using for your SGS2?
Buy something like this one, it supports both http://www.ebay.com/itm/3-3V-5-5V-F...er-Module-for-Arduino-Mini-Port-/380717046158
 

reinsn

Member
Jan 6, 2013
36
28
Sorry you misunderstood me. I don't want to interface a serial console from my i9300. I want to interface the i9300 itself.

Anyway I'll order a controller which supports both 3,3V and 5V TTL levels. If I find out by myself I'll post the solution here.

If anybody knows by experience the answer would still be appreciated :)
 

scholbert

Senior Member
Aug 1, 2007
1,347
813
Hi reinsn!

Sorry you misunderstood me. I don't want to interface a serial console from my i9300. I want to interface the i9300 itself.

Anyway I'll order a controller which supports both 3,3V and 5V TTL levels. If I find out by myself I'll post the solution here.

If anybody knows by experience the answer would still be appreciated :)

You're correct there's not much related to GT-I9300 but you may find information about some of the older devices.
Anyway, the signals are handled by MAX77693 chip on the mainboard.
By using the correct resistor at the ID pin, the data lines of MAX77693 switch to UART mode.
There's an internal multiplexer for that.

As these lines transfer USB data as well, these I/Os should be 5V tolerant, but i guess they are set to 3.3V output voltage in this mode.
A standard FTDI UART should do the job...

For further information see this technical thread:
http://forum.xda-developers.com/showthread.php?t=1629359

P.S.: Internally all I/O to the Exynos use 1.8V level

Regards,

scholbert
 
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reinsn

Member
Jan 6, 2013
36
28
Hi reinsn!



You're correct there's not much related to GT-I9300 but you may find information about some of the older devices.
Anyway, the signals are handled by MAX77693 chip on the mainboard.
By using the correct resistor at the ID pin, the data lines of MAX77693 switch to UART mode.
There's an internal multiplexer for that.

As these lines transfer USB data as well, these I/Os should be 5V tolerant, but i guess they are set to 3.3V output voltage in this mode.
A standard FTDI UART should do the job...

For further information see this technical thread:
http://forum.xda-developers.com/showthread.php?t=1629359

P.S.: Internally all I/O to the Exynos use 1.8V level

Regards,

scholbert

Thank you for your information. I already found the infos I was searching for and made a guide: http://forum.xda-developers.com/galaxy-s3/general/info-i9300-uart-guide-how-to-talk-to-t2928854.

The TTL levels on UARTs serial line are 3,3V.
 

bahtsiz_bedevi

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Dec 12, 2011
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izmir, Turkey
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reinsn

Member
Jan 6, 2013
36
28
I read about a more privileged instruction set available when using UART, but was not yet able to see any difference. Only difference I noticed UART-connection is stable and USB modem connection breaks when screen goes off.
 
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