[Galaxy S III General] scholbert:
Dear Hardware Hackers, Geeks and Modders,

it always takes some time for me to switch over to a "new" device ;)

Recently i bought a GT-I9305 for cheap, to be more exactely bought two; a broken and a working one.

Anyway, as always i need to disassemble my toys, see what's inside and investigate how things work out on the hardware base.

To follow my descriptions and findings in this thread it is recommended to grab the service manual, e.g. at cpkb.org.

As usual there are already many technical threads covering some of the hardware issues.

It's time to put some light on the unknown details here.

Starting a few weeks ago there'd been some time for reverse engineering, study documents, read posts and draw some conclusions.

I hope you'll enjoy my discoveries and give some feedback.

It might take some time though to write down everything even more detailed and get it little bit structured to post it here.

SD-card mode or complete brick recovery by re-write internal bootloader:

The sboot bootloader is capable to start from external SD-card as well and detects the media it has been started from.

To re-write the bootloader in the internal eMMC, we need an external boot media and block the internal boot process at power up.

The SD-card needs a special structure with the sboot binary right in place.

There's already a detailed thread about this procedure (see the reference links below).

Anyway, as you might have read elsewhere, replacing KNOX bootloader with an older one will not work.

The first time a KNOX bootloader is installed on the device,

some hardware protected blocks on the eMMC become active to meet the requirements of the KNOX function.

This process could not be reverted by simply overwrite the sboot section.

We need other tools for this. This might be covered later.

Prevent booting from internal eMMC by blocking MMC_CMD:

GT-I9300:

eMMC44_CH4: MMC_CMD is blocked by shorting the pull-up resistor R313

GT-I9305:

eMMC44_CH4: MMC_CMD is blocked by shorting the pull-up resistor R634

Please refer to the service manual for the correct position of the components.

Bootloader recovery will need some proof of concept, to be 100% certain that it works in the same way, as it does on GT-I9300.

SD-card booting by changing the CPU boot mode (permanently):

The boot code is set at power up by reading the logic level at special IO pins (XOM6:0).

These logic levels are set by a bunch of resistors and could be tweaked.

The boot modes for Exynos 4412 known so far:

XOM[5:1] : 1st device : 2nd device
5b'00010 : SDMMC_CH2 : USB
5b'00011 : eMMC43_CH0 : USB
5b'00100 : eMMC44_CH4 : USB
5b'10011 : eMMC43_CH0 : SDMMC_CH2
5b'10100 : eMMC44_CH4 : SDMMC_CH2

GT-I9305 (default, might need some approval by reading the registers):

XOM[5:1]
5b'10100 : eMMC44_CH4 : SDMMC_CH2

XOM0 : R612 10K PU
XOM1 : R614 100K PD
XOM2 : R615 100K PD
XOM3 : R609 10K PU
XOM4 : R616 100K PD
XOM5 : R610 10K PU
XOM6 : R617 100K PD

GT-I9305 (SD-card boot mode, needs testing!!!):

XOM[5:1]
5b'00010 : SDMMC_CH2 : USB

XOM0 : R612 10K PU (no change here)
XOM1 : R614 100K PD (no change here)
XOM2 : R615 10K PU (changed from PD to PU)
XOM3 : R609 100K PD (changed from PU to PD)
XOM4 : R616 100K PD (no change here)
XOM5 : R610 100K PD (changed from PU to PD)
XOM6 : R617 100K PD (no change here)

This relationship had been partly reverse engineered and concluded from other designs.

May need some approval though.

Same here, external booting from SD-card will need some proof of concept, to be 100% certain that it works without flaws.

There's a uncertainty concerning standard sboot, to allow a complete boot into system level (e.g. recovery) using a non default boot mode.

Maybe the code is bound to the device (internal eMMC only) in some way, or external SD-card is not fully supported as boot media.

Anyway, it is straight forward to build up a SD-card for testing.

The kernel boot parameter and parts of recovery image will need some tweaks to use the right device to boot from.

Direct access to Exynos 4412 debug UART:

The debug UART is permanently accessible on connector HDC401 (no need to block the USB port for this feature).

AP_TXD : HCD401, pin 11 (LVTTL 1.8V)

AP_RXD : HCD401, pin 17 (LVTTL 1.8V)

Please refer to the service manual for the position of connector HCD401.

These signals are fully tested and working.

The best would be to get the counter part of Panasonic AXE620124AW1 for a direct connection,

but this parts seems tobe hard to find.

As an alternative you'll need some very fine soldering iron and some tiny wires.

This way you could solder the wires directly to the pins of the connector.

You'll need some 1.8V level converter (+ USB UART) as already to be found in many projects.

Set up your terminal to 8N1 at 115200Bit/s and there you go.

E.g. enter S-Boot command line by hitting enter at boot up:

PMIC rev = PASS2(4)
cardtype: 0x00000007
SB_MMC_HS_52MHZ_1_8V_3V_IO
mmc->card_caps: 0x00000311
mmc->host_caps: 0x00000311
mmc_initialize: mmc->capacity = 30777344

Samsung S-Boot 4.0-1153417 for GT-I9305 (May 29 2013 - 17:22:39)

EXYNOS4412(EVT 1.1) / 2047MB / 15028MB / Rev 2 / I9305XXBME3

initialize_ddi_data: usable! (0:0x0)
PARAM ENV VERSION: v1.0..
init_fuelgauge: fuelgauge power ok
get_battery_detect: battery is missed
init_fuelgauge: battery is not detected, vcell(3858), soc(59)
init_fuelgauge: POR status
fuelgauge_por: POR start: vcell(3858), vfocv(3871), soc(59)
fuelgauge_por: update SDI M0 parameter
fuelgauge_por: RCOMP(0x0063), TEMPCO(0x0930)
fuelgauge_por: POR finish: vcell(3856), vfocv(3901), soc(55)
get_table_soc: vcell(3855) is caculated to t-soc(62.486)
init_fuelgauge: start: vcell(3855), vfocv(3898), soc(55), table soc(62)
init_fuelgauge: finish: vcell(3855), vfocv(3898), soc(55), table soc(62)
init_microusb_ic: MUIC: CONTROL1:0x00
init_microusb_ic: MUIC: CONTROL1:0x00
init_microusb_ic: MUIC: CONTROL2:0x3b
init_microusb_ic: MUIC: CONTROL2:0x3b
PMIC_ID = 0x02
PMIC_IRQSRC = 0x00
PMIC_STATUS1 = 0x10
PMIC_STATUS2 = 0x00
PMIC_PWRON = 0x02
PMIC_IRQ1 = 0x0c
PMIC_IRQ2 = 0x00
s5p_check_keypad: 0x0
s5p_check_reboot_mode: INFORM3 = 0 ... skip
s5p_check_upload: MAGIC(0xc0c0c0c0), RST_STAT(0x10000)
microusb_get_attached_device: STATUS1:0x38, 2:0x00
s5p_check_download: 0
microusb_get_attached_device: STATUS1:0x38, 2:0x00
check_pm_status: chargable jig, LPM boot
AST_CHARGING..
cmu_div:1, div:7, src_clk:800000000, pixel_clk:57153600
s6e8ax0_read_id :: retry: 1
s6e8ax0_read_id :: 0xd1
<start_checksum:373>CHECKSUM_HEADER_SECTOR :4096
<start_checksum:375>offset:50, size:6296
<start_checksum:379>CHECKSUM_HEADER_INFO : NeedChecksum:0 PartNo:20
Not Need Movinand Checksum
Movinand Checksum Confirmation Pass

autoboot aborted..
S-BOOT #
S-BOOT # help
Following commands are supported:
* chipinfo
* help
* log
* reset
* boot
* load_kernel
* printenv
* setenv
* saveenv
* findenv
* checksum_need
* usb
* upload
* keyread
* readadc
* usb_read
* usb_write
* sdcard
* mmcdtest
* fuelgauge
To get commands help, Type "help <command>"
S-BOOT #

That's it by now!

Consider this as a starter, i'll try to add, correct or change some things from time to time and i hope it's human readable :p

Please give me some feedback or tell me your thoughts

I will add pics as soon as possible and further details if there's some interest.

I will also give some credits soon, because some of these findings are based on information from the curious around here ;)

Credits:

AdamOutler

E:V:A

References:

GT-I9300 hard-brick-fix

http://xdaforums.com/galaxy-s3/general/galaxy-s-iii-gt-i9300-hard-brick-fix-t1916796

Totally Revolutionary SDCard Bootloader For Galaxy S III

http://xdaforums.com/galaxy-s3/general/totally-revolutionary-sdcard-bootloader-t2061437

Port SDCard Recovery to Other Exynos4412 Devices

http://xdaforums.com/showthread.php?p=34732948

Knox reset

http://xdaforums.com/showthread.php?t=2504258

eMMC sudden death research

http://xdaforums.com/showthread.php?t=2096045

NOTE:

I am not responsible for any damaged devices.

The technical information may need some verification by experiments!

It would be nice to add a remark and refer to this post, if you use the pics and information from this thread :highfive:

Cheers,

scholbert