|
|
|
|
Summary
|
|
|
|
|
=======
|
|
|
|
|
|
|
|
|
|
LEGO MINDSTORMS EV3 is a toy robot produced by the LEGO Group. It is based
|
|
|
|
|
on the davinci da850 evm. The EV3 has a 16MB spi flash and a SDHC microSD card
|
|
|
|
|
reader.
|
|
|
|
|
|
|
|
|
|
Booting
|
|
|
|
|
=======
|
|
|
|
|
|
|
|
|
|
The EV3 contains a bootloader in EEPROM that loads u-boot.bin from address 0x0
|
|
|
|
|
of the SPI flash memory (with a size of 256KiB!). Because the EEPROM is read-
|
|
|
|
|
only and it takes care of low level configuration (PLL and DDR), we don't use
|
|
|
|
|
U-Boot to produce an SPL image.
|
|
|
|
|
|
|
|
|
|
Using the default configuration, U-Boot had a boot scrips that works as follows:
|
|
|
|
|
|
|
|
|
|
* Check to see if microSD card is present
|
|
|
|
|
* If it is, try to load boot.scr from the first FAT partition
|
|
|
|
|
* If loading boot.scr was successful, run it
|
|
|
|
|
* Otherwise, try loading uEnv.txt
|
|
|
|
|
* If loading uEnv.txt was successful, import it
|
|
|
|
|
* If there is a uenvcmd variable (from uEnv.txt), run it
|
|
|
|
|
* Try to load uImage from the first FAT partition
|
|
|
|
|
* If it was successful, try to load da850-lego-ev3.dtb
|
|
|
|
|
* If loading uImage was successful, boot it (DT is optional)
|
|
|
|
|
* If none of the above was successful, try booting from flash
|
|
|
|
|
|
|
|
|
|
Suggested Flash Memory Layout
|
|
|
|
|
=============================
|
|
|
|
|
|
|
|
|
|
The following is based on the default U-Boot configuration:
|
|
|
|
|
|
|
|
|
|
| Image (file) | Start Addr. | Max. Size |
|
|
|
|
|
+--------------------+-------------+-------------------+
|
|
|
|
|
| u-boot.bin | 0x0 | 0x40000 (256KiB) |
|
|
|
|
|
| da850-lego-ev3.dtb | 0x40000 | 0x10000 (64KiB) |
|
|
|
|
|
| uImage | 0x50000 | 0x400000 (4MiB) |
|
|
|
|
|
| rootfs (squashfs) | 0x450000 | 0xa00000 (10MiB) |
|
|
|
|
|
|
|
|
|
|
Writing image to flash
|
|
|
|
|
======================
|
|
|
|
|
|
|
|
|
|
The EEPROM contains a program for uploading an image file to the flash memory.
|
|
|
|
|
The program is started by holding down the right button on the EV3 when powering
|
|
|
|
|
it on. You can also `run fwupdateboot` in the u-boot shell to reboot into this
|
|
|
|
|
mode. The image can then be uploaded using the official LEGO MINDSTORMS EV3
|
|
|
|
|
software or a 3rd party program capable of uploading a firmware file.
|
|
|
|
|
|
|
|
|
|
If you are booting from the microSD card, it is enough to just write uboot.bin
|
|
|
|
|
to the flash. If you are not using a microSD card, you will need to create an
|
|
|
|
|
image file using the layout described above.
|
