Hello,
I've been using a Sercomm H500-s with an older OpenWRT version (probably 23.x, or even 22.x, but not sure) and sysupgraded it to the current supported release 25.12.0. The router didn't come online, it was stuck with the green power led. I tried going back to factory firmware using the procedure explained on the device page, and it worked. Then I flashed OpenWRT again and had the same issue.
So, I disassembled and connected to the main soc UART to obtain some logs and compare them with the ones in the device page, and I discovered it's trying to boot to the backup image:
***************************************************
Sercomm Boot Version 0.0.4.0
***************************************************
Entering Firmware : Everything is OK.
Boot Flag's Magic Found at 6a20000.
Boot Flag's Magic Found at 6b60000.
Find bootFlag successfully.
BootFlag1: eRcOmM.000
BootFlag2: eRcOmM.001
Booting from backup image (0xbb820000) ...
Checksum ... OK!
While in the bootlog present in the device page, it's booting from the first image:
***************************************************
Sercomm Boot Version 0.0.4.0
***************************************************
Entering Firmware : Everything is OK.
Boot Flag's Magic Found at 6920000.
Boot Flag's Magic Found at 6a60000.
Find bootFlag successfully.
BootFlag1: eRcOmM.008
BootFlag2: eRcOmM.007
Booting from first image (0xb8520000) ...
Checksum ... OK!
Correctable ECC Error detected: addr=0x006ac000, intrCtrl=0x000000B0, accessCtrl=0xE3441010
Decompression LZMA Image OK!
Entry at 0x80010000
Closing network.
Disabling Switch ports.
Flushing Receive Buffers...
2 buffers found
Closing DMA Channels
Starting program at 0x80010000
[ 0.000000] Linux version 5.4.43 (dani@tool) (gcc version 8.4.0 (OpenWrt GCC 8.4.0 r13247-631c437a91)) #0 SMP Sun Jun 7 18:59:39 2020
[ 0.000000] Detected Broadcom 0x63268 CPU revision d0
[...]
The documentation page doesn't say how to switch boot image. In an AP I have it was just matter of flashing the firmware two times in a row (it switched image every time you flashed it, so flashing it twice you made sure it ended in both images), but I can't flash it twice because in this router, the original firmware reboots the router as soon as the flashing completes successfully.
I tried padding a firmware image with zeroes so it ended up in the "backup" address, but it didn't work (or I didn't do it right...).
Any other idea?