I have a Ubiquity Nano Station M5 with FW version XW.v6.1.7. (HW rev. 1901K)
I tried several methods to downgrade the stock FW so that I'm able to install openWRT, but I failed.
Any FW older then v6.1.4 are giving me the error code A12. Root cause seems to be the fact that Ubiquiti has changed the HW for newer Nano Stations M5. It seems this has changes since HW revision 1847G .
Together with @guifipedro I was able to start to compare the dmesg of an 'old' device with openWRT and a 'new' device with v6.1.4 FW. Up to now our findings are, that the flash chip has changed, which seems to be ath-nor0 now.
I'm writing this to raise awareness that:
- you are not able to downgrade the AirOS FW to a point where you can install openWRT via the web console or tftp
- It's highly possible that the actual openWRT image for the NanoStation M5 is not bootable with the newer HW revisions.
Next steps will be to open the box to access the serial console (who needs warranty of a useless device, if you can't install openWRT anyway...) and try to see if I can overwrite the kernel with an openWRT one via the serial console and u-boot. If anyone is working on something similar or wants the help, please let me know.