Load dtb file sequence

I should load the dtb file before “press a key before autoboot”,
what I have to change in the variables of the environment string?
Thanks in advance.

It depends on module version you have.
In case of 1GB module (eMMC) dtb files located at /dev/mmcblk0p1 partition. You can replace existing dtb file or add a new one. In last case you will need to modify U-Boot env variable to point to your new dtb name.

emmcboot=run setup; setenv bootargs ${defargs} ${emmcargs} ${setupargs} ${vidargs}; echo Booting from internal eMMC chip...; run m4boot && load mmc 0:1 ${fdt_addr_r} **${soc}-colibri-emmc-${fdt_board}.dtb** && load 

Replace ${soc}-colibri-emmc-${fdt_board}.dtb with your file name.

Other Colibri iMX7 modules utilize a raw NAND as a storage. DTB file located at UBI partition1 dev/ubi0_1. To replace it from Linux please use

ubiupdatevol /dev/ubi0_1  <DTB file>

There is no file system on dev/ubi0_1 so there is no need to modify U_Boot variables. Saving new DTB just replaced old one.