f203a479e7
This updates the LEGO MINDSTORMS EV3 boot script to try loading a uEnv.txt file and a da850-lego-ev3.dtb device tree during boot. Signed-off-by: David Lechner <david@lechnology.com>
53 lines
2.1 KiB
Plaintext
53 lines
2.1 KiB
Plaintext
Summary
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=======
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LEGO MINDSTORMS EV3 is a toy robot produced by the LEGO Group. It is based
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on the davinci da850 evm. The EV3 has a 16MB spi flash and a SDHC microSD card
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reader.
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Booting
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=======
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The EV3 contains a bootloader in EEPROM that loads u-boot.bin from address 0x0
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of the SPI flash memory (with a size of 256KiB!). Because the EEPROM is read-
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only and it takes care of low level configuration (PLL and DDR), we don't use
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U-Boot to produce an SPL image.
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Using the default configuration, U-Boot had a boot scrips that works as follows:
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* Check to see if microSD card is present
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* If it is, try to load boot.scr from the first FAT partition
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* If loading boot.scr was successful, run it
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* Otherwise, try loading uEnv.txt
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* If loading uEnv.txt was successful, import it
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* If there is a uenvcmd variable (from uEnv.txt), run it
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* Try to load uImage from the first FAT partition
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* If it was successful, try to load da850-lego-ev3.dtb
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* If loading uImage was successful, boot it (DT is optional)
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* If none of the above was successful, try booting from flash
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Suggested Flash Memory Layout
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=============================
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The following is based on the default U-Boot configuration:
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| Image (file) | Start Addr. | Max. Size |
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+--------------------+-------------+-------------------+
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| u-boot.bin | 0x0 | 0x40000 (256KiB) |
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| da850-lego-ev3.dtb | 0x40000 | 0x10000 (64KiB) |
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| uImage | 0x50000 | 0x400000 (4MiB) |
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| rootfs (squashfs) | 0x450000 | 0xa00000 (10MiB) |
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Writing image to flash
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======================
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The EEPROM contains a program for uploading an image file to the flash memory.
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The program is started by holding down the right button on the EV3 when powering
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it on. You can also `run fwupdateboot` in the u-boot shell to reboot into this
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mode. The image can then be uploaded using the official LEGO MINDSTORMS EV3
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software or a 3rd party program capable of uploading a firmware file.
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If you are booting from the microSD card, it is enough to just write uboot.bin
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to the flash. If you are not using a microSD card, you will need to create an
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image file using the layout described above.
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