I have the same device, bricked it for almost the same reason, the section where you should use a .bin image from OEM based on whether it has 'boot' or not is wrong, I didn't have the 'boot' in the image and therefore should've no problem flashing the original firmware back, I had the same problem with sysupgrade, it didn't work, so I used the mtd method, which bricked the device since it loops the same sequence with the LED's flashing, I also tried TFTP methods based on hardware similarities with older routers and failed.. I then bought a USB TTL device and used telephone wires for the connection.. a multimeter was used to check UART TX,RX,GND,VCC, and I'm not so sure it's the same as in the picture, from left to right, the first two have voltage of about 2.7 each the others don't, using a continuity test the 3rd was the only one to beep with other components in the circuit board and I deemed it to be GND, so if I checked it right the image holds up, yet after connecting GND, TX, RX and flipping both TX and RX, fired up 'screen /dev/ttyUSB0 and started to wait for something to show up (shorting the wires intentionally proved the TTY was working since it printed some characters), connected the device to its power adapter and nothing... after a few tries I thought maybe its something with the ground, shifting the ground cable caused a blackout... I have NO IDEA as to why there's no response... but it's very similar to this.
a few notes about the pictures:
I used analog voltage, I later switched to DC and got 2.7V.
Telephone wires are securing the device to the USB TTL
I don't like that telephone wire arrangement at all you should get three actual square pins and either solder them in or push them in the holes and tilt to the side so they make contact. The other end of the pins would go in the female sockets of your jumper wires.
Have you set the baud rate? I use picocom instead of screen it lets you set the baud rate in the same command line.
I have been able to restore it , but with firmware openwrt 18.06.5 sysupgrade. I think that with stock firmware is also restorable. NOTE: I can't save the config settings with openwrt, erase all turning off the device.
You have to bridge 2 points (try it first with Tx and test it, after Rx). Note: you'll need usb to rs232 ttl converter module, pins working at 3.3V (TTL level voltage).
Setting ip pc to 192.168.1.10, run tftp server (tftpd32) on ethernet interface, download lastest firmware openwrt 18.06.5 sysupgrade version, rename to firm.bin (for easy use). Note: data (firmware) is sent on ethernet interface, commands are sent on serial interface UART. Note:openwrt 18.06.5 sysupgrade
Setting baud rate to 115200 (PuTTY console), no flow control. Note: I have stopped loop with typing tpl.
In my case setting to 128000 can see characters but not stop loop.I have stopped loop, setting baud rate to 115200 and only connecting Rx on device (repeater). Because if connect Tx too, i can see rare characters, and cant use ctrl-v, which interfere with ctrl-v.
Conclusion I did it without seeing.
During "Autobooting in 1 seconds" type tpl. Note: open notepad, typing tpl, select it all, copy for use it into console (PuTTY) with click right or ctrl-v.
set where to find for file firm.bin
copy firm.bin from tftp to ram memory (0x80060000 address).
erase 0x380004 (3670020 Bytes) from flash memory (starting at 0x9f020000).
copy firm.bin stored in ram to flash memory (0x380004 Bytes).
please someone help me, i got same device, i already soldering the serial and iam using Prolific PL2303 Adapter. when iam using "putty" there no respon on putty. how to fix it?
thanks, sorry for my bad english
Either you have the same problem as me, or your TX and RX are flipped, if the problem persists, then go over these:
Is your USB to TTL dongle showing in 'ls /dev/ttyUSB*' and is it working properly? (connect ONLY THE DONGLE and short its GND and RX / GND and TX, it should show something in your emulator as a response)
Make sure your emulator is set to 115200 BAUD rate and with no flow control
Make doubly sure that GND, TX and RX are in the correct order
Don't use VCC, use OEM power source
If you soldered pins make sure they don't short each other by a bad connection (use a multi-meter) with its continuity test function and check the pins don't short each other via a bad solder connection
If you tried the above... then welcome to where I am...
By bridging he meant to short them if I'm not wrong, in order to change the serial mode (https://openwrt.org/docs/techref/hardware/port.serial#serial_modes), it's possible with a simple telephone wire.. you simply use it to "bridge" between two pins.. careful though... a bit unstable with your hands you will get jolted (like I did), I tried to do so with GND+TX and GND+RX.. no change... device is probably completely bricked... at least I can finally give it up.
The same thing happened to me, those who have trouble soldering the points on the board connect them directly to the point without soldering it (by hand).
As I said, I only use RX device(wa850re), and TX TTL USB adapter.