Odin mode (or Download mode) is for Samsung Galaxy phones what the name means — you are a God. In Odin mode, the user is able to flash whatever wants to the internal flash memory inside the phone by connecting phone to the computer via USB cable. As Odin mode is simple program (in the phone), poor user may not even flash main (Android) system, kernel, recovery system, but this is possible to repartition internal flash and reflash Odin mode itself. If something goes wrong and the Odin mode is broken (erased, rewritten, corrupted), the phone no longer boots and is hard-bricked. So Odin mode is dangerous. Because of this dangerous nature of Odin mode, Odin mode is usually used to only reflash main system or recovery (see warnings below) and if possible, recovery mode is used for flashing (as it is less dangerous).
Entering Odin mode
The Samsung Galaxy device (phone, tablet) is able to enter Odin mode by pressing some keys during device boot (usually Vol-Down + Home + Power). When the device is on Odin mode, application like Odin (or Heimdall) could be used to send data to the flash storage inside the device through USB cable. Check your device documentation (here at XDA) how to exactly enter Odin mode.
Odin mode could be entered by pressing some keys during startup sequence. Samsung Galaxy phones (most of them) has the same key combination (ie: Volume Down + Home + Power ON), but you have to read info for every phone to make sure.
- power off the device
- press Volume Down + Home + Power ON button at the same time and hold them pressed
- with buttons pressed, wait few seconds for warning screen (with yellow triangle with exclamation mark inside)
- read the warning screen
- press Volume Up to continue to Odin mode
- Odin mode is advertised by red text in the left upper corner
If you enter Odin mode mistakenly, you may power off the phone by holding Power button for 10 seconds. Do not interrupt Odin mode if some operation (downloading through USB cable from Odin application) was already started or you brick the phone!
Samsung Galaxy Tab has no hardware Home button, so there is none to press. Just Volume Down + Power ON is enough (for example Samsung Galaxy Tab 7.7).
Flashing with Odin
This is only example. Consult documentation for your device.
- deinstall Samsung Kies from your computer
- download and install Samsung USB drivers
- go to the official Samsung page for your device phone and look into Support section for USB drivers
- example: Galaxy Tab 7.7
- download Odin
- check compatility and required Odin version for your device
- there are Odin versions at http://forum.xda-developers.com/showthread.php?t=2189539
- extract and run Odin (no installation is needed)
- make sure the only checked Options (box on left in Odin) are "Auto reboot" and "F.Reset Time"
- make sure you DO NOT CHECK RE-Partition (!!!)
- click on PDA and pick your custom ROM (in .tar.md5 format)
- if custom ROM is in ZIP format, uncompress it to get .tar.md5 format
- connect USB cable to the phone
- yellow rectangle should appear under ID:COM box and text "Added" in Message box in Odin application
- click Start in Odin application
- wait for download to complete (downloading ROM to the phone)
- you may see log in Message box
- wait for autoreboot (of the device)
- then you may disconnect USB cable from phone
- it may take a long time the phone to fully boot (about 10 minutes is ok)
- you are done!