| David Lechner | 2ac07f7 | 2016-02-26 00:46:07 -0600 | [diff] [blame] | 1 | Summary |
| 2 | ======= |
| 3 | |
| 4 | LEGO MINDSTORMS EV3 is a toy robot produced by the LEGO Group. It is based |
| 5 | on the davinci da850 evm. The EV3 has a 16MB spi flash and a SDHC microSD card |
| 6 | reader. |
| 7 | |
| 8 | Booting |
| 9 | ======= |
| 10 | |
| 11 | The EV3 contains a bootloader in EEPROM that loads u-boot.bin from address 0x0 |
| David Lechner | f203a47 | 2018-05-19 23:25:07 -0500 | [diff] [blame] | 12 | of the SPI flash memory (with a size of 256KiB!). Because the EEPROM is read- |
| 13 | only and it takes care of low level configuration (PLL and DDR), we don't use |
| 14 | U-Boot to produce an SPL image. |
| 15 | |
| 16 | Using the default configuration, U-Boot had a boot scrips that works as follows: |
| 17 | |
| 18 | * Check to see if microSD card is present |
| 19 | * If it is, try to load boot.scr from the first FAT partition |
| 20 | * If loading boot.scr was successful, run it |
| 21 | * Otherwise, try loading uEnv.txt |
| 22 | * If loading uEnv.txt was successful, import it |
| 23 | * If there is a uenvcmd variable (from uEnv.txt), run it |
| 24 | * Try to load uImage from the first FAT partition |
| 25 | * If it was successful, try to load da850-lego-ev3.dtb |
| 26 | * If loading uImage was successful, boot it (DT is optional) |
| 27 | * If none of the above was successful, try booting from flash |
| 28 | |
| 29 | Suggested Flash Memory Layout |
| 30 | ============================= |
| 31 | |
| 32 | The following is based on the default U-Boot configuration: |
| 33 | |
| 34 | | Image (file) | Start Addr. | Max. Size | |
| 35 | +--------------------+-------------+-------------------+ |
| 36 | | u-boot.bin | 0x0 | 0x40000 (256KiB) | |
| 37 | | da850-lego-ev3.dtb | 0x40000 | 0x10000 (64KiB) | |
| 38 | | uImage | 0x50000 | 0x400000 (4MiB) | |
| 39 | | rootfs (squashfs) | 0x450000 | 0xa00000 (10MiB) | |
| David Lechner | 2ac07f7 | 2016-02-26 00:46:07 -0600 | [diff] [blame] | 40 | |
| 41 | Writing image to flash |
| 42 | ====================== |
| 43 | |
| 44 | The EEPROM contains a program for uploading an image file to the flash memory. |
| 45 | The program is started by holding down the right button on the EV3 when powering |
| 46 | it on. You can also `run fwupdateboot` in the u-boot shell to reboot into this |
| 47 | mode. The image can then be uploaded using the official LEGO MINDSTORMS EV3 |
| 48 | software or a 3rd party program capable of uploading a firmware file. |
| 49 | |
| 50 | If you are booting from the microSD card, it is enough to just write uboot.bin |
| 51 | to the flash. If you are not using a microSD card, you will need to create an |
| 52 | image file using the layout described above. |
| David Lechner | 1d259e4 | 2019-05-28 20:56:42 -0500 | [diff] [blame] | 53 | |
| 54 | IMPORTANT: The EEPROM bootloader only copies 256k, so u-boot.img must not |
| 55 | exceed that size! |