3.1.1.5. Environment

3.1.1.5.1. U-Boot Environment

Note

SDK 9.0 will not default to the environments that are saved on the boards, It will default to the ones that are given with the particular uboot in the release.

By default the SDK builds will have the default environments whenever being run, to have some custom environments, one needs to rely on uEnv.txt file.

The added benefit of using uEnv.txt is that it is more granular than the saveenv counterpart as we can choose to store the variables that are actually being set during the development workflow.

Writing to MMC/EMMC

=> env export -t $loadaddr <list of variables>
=> fatwrite mmc ${mmcdev} ${loadaddr} ${bootenvfile} ${filesize}

The following will update the uEnv.txt file on the bootmedia and then whenever “run envboot” is run on the board, uEnv.txt will be read based on mmcdev value to be read either from emmc/sd card.

You can specifically choose the variables that you are changing in your development process so that the other variables are not affected due to the whole environment being saved. Optionally, one can save the full environment too in uEnv.txt by not specifying <list of variables> this will have some issues with the ethernet mac addresses not being overridden but other things will be set.

Reading from MMC/EMMC

By default run envboot will read it from the MMC/EMMC partition ( based on mmcdev) and set the environments.

If manually needs to be done then the environment can be read from the filesystem and then imported

=> fatload mmc ${mmcdev} ${loadaddr} ${bootenvfile}
=> env import -t ${loadaddr} ${filesize}

For production environments if one needs to rely on saveenv counterpart then they can always refer to the commit

Networking Environment

When using a USB-Ethernet dongle a valid MAC address must be set in the environment. To create a valid address please read **this page**. Then issue the following command:

=> setenv usbethaddr value:from:link:above

You can use the printenv command to see if usbethaddr is already set.

Then start the USB subsystem:

=> usb start

The default behavior of U-Boot is to utilize all information that a DHCP server passes to us when the user issues the dhcp command. This will include the dhcp parameter next-server which indicates where to fetch files from via TFTP. There may be times however where the dhcp server on your network provides incorrect information and you are unable to modify the server. In this case the following steps can be helpful:

=> setenv autoload no
=> dhcp
=> setenv serverip correct.server.ip
=> tftp

Another alternative is to utilize the full syntax of the tftp command:

=> setenv autoload no
=> dhcp
=> tftp ${loadaddr} server.ip:fileName