It may not be clear, but the use of a boot script on SD can also be useful in booting over NFS. In this environment, you shouldn’t need to format the SD card at all: FAT32 should work.
As the name implies, U-Boot is the Universal Boot Loader, and it can load and launch Windows Embedded using a boot script in a very similar manner as Linux. There’s no need to use dd or any other special formatting commands. To run Ubuntu, LTIB or Timesys single-partition images, you can create an SD card by simply formatting an ext2/3/4 partition and copy your filesystem image, boot script and kernel using cp. To build an SD card to upgrade U-Boot, you can copy just two files ( 6q_upgrade and u-boot.bin)to a fresh, out-of-the-box SD card (which tend to come formatted as FAT32), insert the card and run run upgradeu. I should probably move this section to the top of the document, but here’s some additional rationale for how and why we use the boot script scheme. reset" doĮcho "Error reading boot loader from EEPROM" Įcho "No U-Boot image found on SD card" $:1 12000000 u-boot.bin thenĮcho "read $filesize bytes from SD card" We’ve pre-configured the bootcmd environment variable to load and launch a boot script from the root directory of either SD card slot by using the looping features of the Hush parser: The flash device size is 2MB, which is plenty of space for the boot loader and environment, but not enough for a complete O/S, and we defer that to SD card, which brings us to the first environment variable: bootcmd Instead, we added a serial flash chip and store the boot loader there. We jokingly refer to this as a game of “Hide the U-Boot”, and don’t want to play. Another pre-configured command clearenv will erase the environment variables in serial flash.īoth of these boards boot to SPI EEPROM (serial flash), and both U-Boot and its’ environment variables are stored there.Ĭonvention for many modern ARM boards, including i.MX in recent years has been to boot directly to SD card, either by using unformatted areas of the disk or carefully placing special files in prescribed areas of a filesystem.A pre-configured command upgradeu can be used to upgrade U-Boot in serial flash.Both of these devices ship with U-Boot configured to load and run a boot script named 6q_upgrade from the root of either SD card.In this blog post, we’ll explain three key environment variable conventions used on the Nitrogen6X (and Sabre Lite before it). A little convention make things easy to use, but only if you know the convention.
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