| 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. |
| |
| IMPORTANT: The EEPROM bootloader only copies 256k, so u-boot.img must not |
| exceed that size! |
