Selecting a USB-TTL adapter and installing OpenWrt onto Asus TIF AX4200

Hi, a newbie here who just got this router and want to install openwrt. I want to make sure I understand everything before I do it, so hope people don't mind shedding some light on my basic questions. Thanks in advance.

The 0x46000000 part is to tell the bootloader from which position/address to boot the image from.

Just be careful with the amount of zeros.

I think any of those adapters will do fine. I choose one that has 5v, 3.3v and 1.8v output because there are some routers that can only take 1.8v.

If you don't want to solder anything then you'll need the cables end in a pin (male) as the Asus board has holes to slot them into to make the serial connection, you just have to be careful not to move any of them.

I personally use this One here

However, you can try me from what you posted as long as it works well with you.

You can check this Post here, it may be useful for you about backup

Any of these USB to UART serial bridges:

Jumper wires:

Test hook clips:

.

This USB programmer:

WSON8 clip to backup or reflash the chip without desoldering:

USB extension cable to connect the USB programmer:

.

Information:

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ch3xxx ttl adapters are bad if you use it on windows 11, works fine if you use it on Windows 10 or older and all Linux platforms.

ill probably go with CP210 or the FTDI ttl adapters if you want the best ttl to use in windows.

I always have issues with CH3xxx using it to reprogram ESP chips. all of that issue no problem with CP210.

though currently im using a esp8266 as a wifi based ttl adapter to basically access serial console of many devices that includes these kind of routers.

flashing the router via TTL always involves using tftp specially on a locked down firmware like asus and tplink. the most common thing you can flash your router with openwrt via ttl is basically let the router boot the intramfs image of openwrt, once it booted up, you can test all the stuff on it before you can make permanent modifications on it (aka flashing openwrt over it) once your satisfied and want to go to openwrt firmware, you can just use go to firmware update page and this time use the sysupgrade image.

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Thx for the reply. So once flashed with openwrt, there is no way back to stock firmware? I already flashed the router without backing up anything first... I was hoping some kind of recoverage method should be able to flash the latest stock firmware back into the router, no?

you probably can go back as long as you did not replace the bootloader. openwrt do not really touch the bootloader part anyway so you should be able to go back to stock firmware if you just follow the asus way to reflash your routers firmware using its windows app or something.

Any updates on that? Has anybody managed to successfully reverts back to the original firmware?

If you made the backup going to openwrt, or if Asus made their fw available for DL, why not ?

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Yes, the method described in filogic: add support for ASUS RT-AX59U was working for me.

1: Download the TUF-AX4200 firmware from ASUS official website ( I've used this one: https://dlcdnets.asus.com/pub/ASUS/wireless/TUF-AX4200/FW_TUF_AX4200_300438832464.zip?model=TUF-AX4200 ). Save the firmware to tftp server directory and rename to TUF-AX4200.trx. (I've used a Windows tftpd from here: https://pjo2.github.io/tftpd64/ )

2: Connect the PC with TFTP server to the TUF-AX4200.
Set a static ip on the ethernet interface of your PC.
(ip address: 192.168.1.70, subnet mask:255.255.255.0)

3: Connect to the serial console, power on again, interrupt the autoboot process by pressing '4' when prompted, then enter the following commands:

$: ubi remove linux
$: ubi remove jffs2
$: ubi remove rootfs
$: ubi remove rootfs_data
$: ubi create linux 0x45fe000
$: reset

then the dut will reboot, interrupt the autoboot process by pressing '2' when prompted.

2: Load System code then write to Flash via TFTP.
Warning!! Erase Linux in Flash then burn new one. Are you sure?(Y/N)
$:

enter y, you will see the followings, hit enter directly:

Input device IP (192.168.1.1) ==:
Input server IP (192.168.1.70) ==:
Input Linux Kernel filename (TUF-AX4200.trx) ==:

4: wait for the device run up

My two cents on the USB-TTL adapters: just make sure it supports 3.3V and that drivers are available for your operating system. For example I have a very old PL-2303HX based USB-TTL adapter, but Windows drivers are no longer available (you can hack it, but it is quite inconvenient) and mine is unstable at the 115200 rate, loosing connection, getting garbage characters (even under Linux)... Currently I'm using a CH340G based USB-TTL adapter ( https://joy-it.net/en/products/SBC-TTL ), so far it seems reliable.

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