Miktorik firmware flashing problem

Hello,
As this is my first post here I'd like to welcome everyone.

I’m trying to install AREDN firmware on a Mikrotik board and I am struggling with that. 

At the beginning I’d like to mention that I have some basic experience with that process - 3 running nodes - 2 of them Mikrotik. Thus the problem isn’t trivial.

The board itself has printed on the label “RouterBOARD 912G 5HPnD”. The sticker says “RB911G-5HPnD FCC ID: TV7RB912G-5HPND”. Therefore I have doubts regarding the actual model.

RouterOS says:

CPU        MIPS 74Kc V4.12
CPU Count        1
CPU Frequency        600 MHz
Total Memory        32.0 MiB
Total HDD Size        128.0 MiB
Architecture Name        mipsbe
Board Name        RB911G-5HPnD
Firmware Type        ar9340
Version        6.49.7 (stable)
Factory Firmware        3.07
Current Firmware        6.49.7

Additionally OpenWRT says:

Architecture    Atheros AR9342 rev 2

And additionally the only AREDN firmware I was able to run says:

Hardware Type: (ar71xx/mikrotik) mikrotik (rb-911g-5hpnd)

I assume that this is the RB911G :)

In the https://downloads.arednmesh.org/snapshots/SUPPORTED_DEVICES.md document there is RB911G-2HPnD listed but the Image column is empty. 

In the https://downloads.arednmesh.org/afs/www I can find MikroTik RouterBOARD 911G-5HPnD-QRT and I assume that this is the correct one.

At the beginning I was faced with the “not compatible with the bootloader of RouterOS v7” issue so I downgraded the Router OS to versions 6.45.8 and later the  6.45.1 and 6.44 - due to failure to install AREDN. 

I have tried to run multiple versions of AREDN firmware. All have failed at some point. To verify if this is some hardware problem I checked if it is doable to install the original OpenWRT. I succeeded at my first attempt. The procedure was exactly the same. Boot from tftp, scp the sysupgrade.bin and run the sysupgrade command. I’m able to perform multiple operations and as far as I can tell it is stable and fully functional.

The first and most worrying problem for me is why I am unable to boot any of versions available trough https://downloads.arednmesh.org/afs/www The boot simply does not start. Ping command replies with “Destination Host Unreachable”. Is the board somehow different to the one you support? Are there some variants? 

While trying multiple versions I found that I am able to boot all the 3.22 versions from ar71xx/mikrotik target.

But is was failing to upload the sysupgrade.bin both via browser and scp. 

Browser was failing with 500 and after then I was unable to access the webpage again.

The scp was failing as bellow.

$ scp -O -v -p 2222 aredn-3.22.12.0-ar71xx-mikrotik-nand-large-squashfs-sysupgrade.bin  root@192.168.1.1:/tmp
Sending file modes: C0664 5560320 aredn-3.22.12.0-ar71xx-mikrotik-nand-large-squashfs-sysupgrade.bin
Sink: C0664 5560320 aredn-3.22.12.0-ar71xx-mikrotik-nand-large-squashfs-sysupgrade.bin
aredn-3.22.12.0-ar71xx-mikrotik-nand-large-squashfs-sysupgrade.bin                                                                                    40% 2208KB  62.7KB/s   00:51 ETA
client_loop: send disconnect: Broken pipe
lost connection

After the operation. System starts being unstable. Webpage does not load. Ssh disconnects randomly. 

$ ssh -p 2222 root@192.168.1.1
root@192.168.1.1's password: 


BusyBox v1.30.1 () built-in shell (ash)

Killed
Killed
Killed
Connection to 192.168.1.1 closed.

I have left it overnight to "warp it up". I was trying to limit the speed with the -l flag. No luck. 

I was able to upload some smaller files but to some size. There is one discovery I made. I was trying to create a file in /tmp directory using different sizes:

root@NOCALL:~# dd if=/dev/zero of=output.dat  bs=1K  count=1024
1024+0 records in
1024+0 records out
root@NOCALL:~# ls -lh | grep output.dat 
-rw-r--r--    1 root     root        1.0M Dec 14 16:07 output.dat
root@NOCALL:~# dd if=/dev/zero of=output.dat  bs=1K  count=4096
Killed
root@NOCALL:~# Connection to 192.168.1.1 closed.

It seems that I am unable to create in the tmpfs a file above a certain size despite available space.

root@NOCALL:~# df -h /tmp
Filesystem                Size      Used Available Use% Mounted on
tmpfs                    13.5M     84.0K     13.4M   1% /tmp

If not for the fact that I was able to successfully boot and flash the OpenWRT and it is running without a hitch I would think that this is some hardware issue. But now I think there seems to be some problem between me and the aredn firmware. 

My question is if I am doing something incorrect? Is this the right approach? Is the board in fact supported? Maybe I am wrong and it in fact is the hardware issue?

I’m going to try the “The old way to flash an image“ approach from here https://openwrt.org/toh/mikrotik/rb91xg_5hpnd but first I wanted to make sure that there isn't any obvious reason I shouldn't do it and there is any chance it will run.

73,
Paweł SQ7PWL