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Accessing uart on Galaxy Nexus i9250

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By, Junior Member on 24th January 2012, 01:57 PM
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I'm going to do some low-level software development on Samsung Galaxy Nexus (replacing kernel with custom one doing stuff that are not Android-related). To do so I'll require accessing uart output of bootloaders and Linux.

I'm looking for an information how to connect to i9250's uart serial port and possibly other stuff.

Currently the best what I've found is The all-in-one Galaxy S2 Hack Pack (, but obviously this is not entirely what I'm looking for. The i9250 service manual maybe some help too. If anyone has any information regarding this matter, please post.
Last edited by; 24th January 2012 at 02:20 PM.
25th January 2012, 07:08 AM |#2  
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Originally Posted by

I'm looking for an information how to connect to i9250's uart serial port and possibly other stuff.

To get access to your kernel's, bootloader's logs through UART you need UART jack(dont know this word in english, I think I guess 'jack') on your board, in your case i9250's.
If developers of board didn't add that jack to pcb design, your attempts to view logs will be unsuccessful.
If you find UART pins of your SoC, connect it to UART-USB converter and plug to your PC.
In bootloader sources you will find to which UART port debug messages will go, if your SoC has more than one controller.
In linux's kernel case debug port you could assign through startup string, like bootargs in uboot, or through menuconfig.

But all this stuff depends on have you got UART pins on board or not.
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20th February 2012, 09:58 PM |#3  
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Originally Posted by

I'm looking for an information how to connect to i9250's uart serial port and possibly other stuff.

First you have to tell us what hardware you have! Find some links to "tear-aparts / tear-downs" etc. Also make sure, what you find, corresponds to your device. Samsung is going wild when it comes to making (incompatible) product variations. When we know the hardware we can start to find out the rest... In your case the most important is to find out about the application processor (AP), baseband processor (P) and the micro-USB mux.
21st February 2012, 01:49 PM |#4  
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Its the Galaxy Nexus GSM/HSPA version. It has an OMAP4460. The processor found on the pandaboard.
21st February 2012, 02:41 PM |#5  
This device should have external UART.

Have you tried 619Kohms on the USB port yet? Most samsung device, including this one, have a FSA chip. This is the first way to tell if UART is properly connected.

If it is, than you can probe deeper to find the internal UART which will show more. The Internal UART connection will show UART before the FSA chip is initialized giving you even more to work with.

It's likely that because this is an OMAP chip, it should have the following characteristics:

192600 or 115200 bps
8 bits per word
1 stop bit
No parity
No flow control
1.8V high, Open drain

I'm not sure if the FSA chip will increase that level to 3V or not.
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22nd February 2012, 12:46 PM |#6  
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To briefly clarify (and confirm) what Adam says.

There is already built in UART-USB functionality controlled by the FSA (MUX). Thus you can just connect an external microUSB connector with appropriate resistor values, to get a serial connection. (Just google "I9x00 USB JIG"). But if you decide to use internal UART pins on the PCB, then you get earlier access to everything and you can start reading already at the IBL (Initial Boot Loader) stage, which are the absolute first characters coming out of phone after a reboot.
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1st March 2012, 11:52 AM |#7  
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I can confirm the 619Kohm trick works on Galaxy Nexus. I used a 3.3V USB/UART breakout card. Serial output:

�����[sbl_board_charger_init_post] : Succeed set model data : 0x78!!!!!
====== VCELL : 368500, SOC : 23, nType : 4 ======
[Charger] nScaledVCELL : 368500000, nDesriedSOC, : 23, nMaxSOC : 43, nMinSOC : 3
[ omap_power_get_reset_source :47] PRM_RSTST : 0x1
[ __omap_usbacc_test_donwload_by_musb :280] nDeviceType : 0x4
[ omap_usbacc_get_reboot_reason :333] nJigStatus = 0x00000001
[ __sbl_board_hw_init_late :719] final reboot mode in cable = 0x20000
[ __sbl_board_hw_init_late :730] Wake up by TA / USB / JIG
* FB base addr = 0xbea70000!
* PANEL_S6E8AA0_ID_READ : 0x12, 0x8e, 0x9f.
[ omap_power_get_reset_source :47] PRM_RSTST : 0x1
message.command =
message.status =
message.recovery =

Starting kernel at 0x81808000...
<hit enter twice to activate fiq debugger>

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7th March 2012, 03:04 PM |#8  
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This is what comes prior to the above, in case anyone is interested.

-- OMAP 00004460 (version 04460e11) PPA release 1.6.1 Hash 30639809--
Device type: HS, DEBUG OFF
CPFROM HAL API support integrated
THERMAL support integrated: Run Time + Boot time
HDCP support integrated
-- PROD PPA RC3.2.3 --
Reset reason = 00037ba2
PRM_RSTST = 00000002
PPA freed 2992 bytes

Texas Instruments X-Loader 1.41 (Nov 16 2011 - 16:28:45)
Starting OS Bootloader from MMC/SD1 ...
CFG_LOADADDR = 0xa0208000
1st instruct = 0xEA000007
[ __omap_twl6030_init_vbat_cfg :49] SA_PHOENIX_START_CONDITION = 0x8
[ __omap_twl6030_init_vbat_cfg :54] SA_PH_CFG_VBATLOWV = 0x80
[ __omap_twl6030_init_vbat_cfg :63] SA_PH_CFG_VBATLOWV = 0x80
[ __omap_twl6030_init_vbat_cfg :86] SA_BBSPOR_CFG = 0x78
17th March 2012, 04:34 AM |#9  
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Now, could we have the English translation (of all that above) please?

[And if debug is OFF, how can we turn it ON?]

I seem to be able to count 4 bootloaders there, how many damn boot loaders are there!?
28th March 2012, 05:24 PM |#10  
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USB - UART 619Kohm cable
Would anyone build a custom 619Kohm mini-USB to UART cable and ship it in the U.S. or India? We need it.

Is there any supplier of this in the U.S.?

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