I'm using https://downloads.openwrt.org/snapshots/targets/ramips/mt7621/ for my ZBT WG3526 16M router. However, since about 10 days I can no longer use the image file to update my router. Today's file dated July 22 09:43:06 while it will flash the router, puts the router in a continuous boot loop.
The latest working image file I have is dated 2019-07-10 and is named "openwrt-ramips-mt7621-zbt-wg3526-16M-squashfs-sysupgrade_2019-07-10.bin". Later image files have the link text "zbtlink_zbt-wg3526-16m-squashfs-sysupgrade.bin" but the actual image file is named "openwrt-ramips-mt7621-zbtlink_zbt-wg3526-16m-squashfs-sysupgrade.bin". There is an added "zbtlink_" to the new image file name.
Old (working): openwrt-ramips-mt7621-zbt-wg3526-16M-squashfs-sysupgrade.bin
New (re-booting): openwrt-ramips-mt7621-zbtlink_zbt-wg3526-16m-squashfs-sysupgrade.bin
As introduced with ath79, DTS files for ramips will now be labelled
soc_vendor_device.dts(i). With this change, DTS files can be
selected automatically without further manual links.
An opkg install command or a flash of the image file downloaded from https://downloads.openwrt.org/snapshots/targets/ramips/mt7621/ still results in the ZBT WG3526 router being stuck in an endless reboot loop. I believe the image file is the wrong one for the ZBT WG3526 16M device.
Or the image (based on DTS info) is built for more or less RAM than the unit in question has. There are 256MB RAM version of the board as well as a 512MB RAM version. You need a build that matches the available RAM as well.
The important memory size in my case is the flash memory. The images available for download are "openwrt-ramips-mt7621-zbtlink_zbt-wg3526-16m-squashfs-sysupgrade.bin" for 16MB flash and the "openwrt-ramips-mt7621-zbtlink_zbt-wg3526-32m-squashfs-sysupgrade.bin" for the 32MB flash memory.
Since I have the 16MB flash version, I always select the 16MB image file (The 16Mb and the 32Mb image files are identical in size!). This worked fine up until and including the 2019-07-10 image file. After this date, flashing the router with the openwrt-ramips-mt7621-zbtlink_zbt-wg3526-16m-squashfs-sysupgrade.bin image, puts the router in a boot loop.
A few times I have flashed my router, by mistake, with the 32MB image file and with the same boot loop error I now experience.
So yes, I have selected the correct image file, at least by it's name, but after flashing the router, it keeps rebooting endlessly.