RT-AX56U, E5787 and USB CDC-NCM

[edzat1]

You are reading a first sharing from Linux beginner who try to use un-support-ed USB device..
I got old E5787, used RT-AX56U and want to draw USB powered from router to mifi..

At the beginning, I found several way and required manual intervention (or JFFS scripting)..
To avoid that hustle then no choice but to compile the firmware..

It is using no-brain solution by updating "55534243123456780000000000000011062000000101000100000000000000" to "55534243123456780000000000000011063000000000010000000000000000" in usb_modeswitch.c:

else if (ModeMap & HUAWEINEW_MODE) {
        SHOW_PROGRESS(output,"Using standard Huawei switching message\n");
        detachDriver();
        strcpy(Messages[0],"55534243123456780000000000000011063000000000010000000000000000");
        switchSendMessage();
    }

Those string referred from usb_modeswitch_modes.md:
CDC Ethernet mode: 55534243123456780000000000000011062000000101000100000000000000
CDC NCM (modem) mode: 55534243123456780000000000000011063000000000010000000000000000

Then, compile the firmware..you can take a shortcut by using amcfwm..after updating usb_modeswitch.c file, I made a little adjustment by commenting two lines in amcfwm.sh as I need stable version (git checkout 386_2.6):

# git checkout "$BRANCH" >/dev/null 2>&1
# git pull origin "$BRANCH" >/dev/null 2>&1

The rest is the finding..

Spoiler: result

Initially, E5787 recognized as [12d1:1506] and it will not switch anymore so you won't have wwan0 interface..
However with the trick, Merlin's firmware will auto switch the modem USB ID from [12d1:15ca] to [12d1:155e]..

Using iperf (which is copied from E5787 firmware to RT-AX56U), direct USB connection able to exceed >100Mbps..

Spoiler: iperf

Measuring WAN by using Speedtest ended up with >80Mbps (DL) which is good enough for me..

Spoiler: speedtest

Take note that LTE coverage at my place is not so good..

Spoiler: reception

I noticed that WAN LED is not blinking and don't know how to remap it:

Spoiler: led

BTW, I also had E8372 and E5577 which work fine using USB CDC-Ether without any modification to the firmware..

THAT'S ALL and THANK YOU..!