The Routerboard RB750Gr3 (aka Hex3) is a nice and very affordable (~$60) hardware platform based on the MediaTek MT7621AT. It features gigabit ethernet ports, and a relatively fast multi-core CPU. However, out of the box it runs RouterOS. While this is a feature-full platform, I found configuration difficult and not very pleasant. Hoping that a build of OpenWRT/LEDE would soon become available, I bought an RB750Gr3 a couple of months ago.
A build became available, but it couldn’t be flashed on the RB750Gr3 without external hardware like a bus-pirate. But this has recently changed, and it’s now possible to TFTP boot a LEDE runtime, which allows access to write to the flash/mtd. Using this method it’s now possible to install OpenWRT/LEDE and upgrade uboot on the device without external hardware.
The OpenWRT site documents this procedure nicely, however, it’s still quite a lot of work to build all the required images and files. So I’ve deciced to host the images that I’ve created here, so other people can skip this rather tedious step of building the image.
The files can be found on https://rb750gr3.sigio.nl/
Please update factory.bin with your own MAC address at offset E000. Currently it’s set to 64:D1:54:AA:BB:CC
You can then netboot/tftpboot using the file ‘vmlinux-initramfs.elf’ (boot the RB750 and hold RESET until the leds stop flashing)
Wait for the system to come up on 192.168.1.1
Login as root
Copy the factory.bin uboot.bin uboot-env.bin and lede-17.01.2-ramips-mt7621-rb750gr3-squashfs-sysupgrade.bin to the system (in /tmp for example)
mtd write (without reboot) the 4 files to the relevant partitions (cat /proc/mtd to see the names/devices)