[Gta04-owner] not booting?

Dr. H. Nikolaus Schaller hns at goldelico.com
Sat Oct 22 11:09:09 CEST 2011

Hi Michael,

Am 21.10.2011 um 22:35 schrieb Michael Spreng:

> Hello
> Today I assembled my gta04. Then I perform the steps as described in the
> makesd script and prepared an sd card for booting. But unfortunately it
> doesn't boot. It behaves exactly the same as if I didn't insert the
> microSD, only the back light of the LCD goes on. What could I do?

Most likely it is the formatting of the SD card. The FAT partition needs a
special number of cylinders etc. so that the file called "MLO" is at a
specific position. The reason is that the Boot ROM of the OMAP processor
does not understand FAT completely, but only sectors and cylinders.

Therefore it is also important that the file MLO is copied onto the SD
card as the first file. If you overwrite it or write a new copy, the new one
will not be at the right position and since the old one is marked as
free sectors, you may overwrite it with other data blocks blocks.

The detailled boot process is:

1. Battery is inserted
2. backlight goes on
3. the RS232 should show a "60" message. This is not really a
readable message but an indicator that the ROM is optionally
waiting to receive a bootloader (a variant of MLO) through the
RS232 interface.
4. the SD card is read (you can check that the VMMC1 test point
goes to 3.3V)
5. after the MLO file is loaded into the 64 kByte SRAM it is started
6. one of the first steps of MLO is to switch off the backlight
So if the backlight flickers, MLO is being loaded
7. then, MLO has a real MMC/FAT driver and locates the file
8. this one is loaded into the big SDRAM
9. and started
10. the u-boot code switches on the backlight again (ca. 1 sec after battery insertion)
11. and initializes I2C, RS232 etc. and starts to emit the welcome
12. it waits a little if the user wants to break into the u-boot console
13. if not, u-boot runs the boot.scr (if possible)
So if the boot.scr file is missing, u-boot will then wait here and nothing
more happens
14. the boot.scr as we provide it then initializes the framebuffer
and tries to load a boot-splash bitmap (after ca. 5 seconds)
15. then, it switches on the red power LED
16. then, it locates the kernel (uimage.bin) and switches the power LED to yellow
17. after sucessfully loading the kernel it switches the LED to green (after ca. 10 seconds)
18. now, the kernel is being started

So basically there are three tools/indicators to check what is going on:
* backlight flicker - indicates if MLO did load from SD card
* power LED going red to green - indicates u-boot is up and loading a kernel
* RS232 - U-Boot console and kernel boot log

And finally, there is the NAND flash. If it contains an XLO (variant of MLO)
and u-boot and kernel, the device can boot from NAND.

Here, the AUX button can force the boot ROM to change the search order.
If the AUX button is pressed while the battery is inserted, the boot ROM
will try the SD card before NAND for XLO (loads U-Boot from NAND)/MLO
(loads U-Boot from MMC/SD). If there is no valid XLO in NAND, the boot ROM
always looks for a MLO on SD card.

The AUX button is checked again by U-Boot which opens a boot splash

I hope this description of the boot process helps to debug the issues.


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