How to “unbrick” your node after a failed firmware upload.

I had a node that failed to upload the AREDN firmware a while back, but it was a spare, so it got tossed on the shelf and I figured I would see if I could bring it back to life later. that day finally came today, and I will say that the process is actually pretty easy. It took a bit of searching to find the instructions, and the credit does not go to me for this,  This Process will take your node back to stock Ubiquiti Firmware and from that point, you can Upload the AREDN firmware. The instructions for that process can be found here.

Here is what is needed

USB-TTL Cable (I got mine on amazon for $6.99 Amazon Link
Ethernet Cables
POE Converter
Bricked Device
TFTP  Application (I used the TFTP application built into Windows, you may need to go to the “Turn windows features on or off” section to turn on TFTP client)
Firmware File (Can be downloaded from the Ubiquiti site https://www.ubnt.com/download/)
Putty terminal

Here are the steps

1. Open up the device and locate the serial jumper. On my NanoBridge, this is a 4 pin header, yours may be different and take a google search to find it.

Ubiquiti NanoBridge TFTP

Note that the Red VCC pin is not used, just Ground, TX, and RX.

2. Connect the USB-TTL Cable to the jumper
—3.3V+ (Red: Do not connect)
—2. S-in (GREEN)
—3. S-out (White)
—4. GND(Black)

3. Now we need to open a Serial connection with the port that the USB-TTL device is plugged into.   If you are unsure of what port your adapter is on, you can Search in windows for Computer Management -> Device Manager -> Ports.  the port needs the following settings

—Bits per second: 115200
—Data Bits : 8
—Stop Bits : 1
—Parity : None
—Flow control : None

Open Putty and select the Serial Radio button.
set Serial Line to the comport Being used (example COM1).
Set the Speed to 115200.

4. Plug the POE adapter into the wall.

5. Plug the LAN side of the device into your PC.

6. Configure your PC IP settings to the following:
—IP Address: 192.168.1.10
—Netmask : 255.255.255.0

7. Connect the POE side of the POE adapter into the bricked device.

8. Continually press any key while the tera-term window is selected. Doing this will interrupt
the boot sequence and allow you to enter terminals while the device is in the bootloader.

9. Once the boot has been stopped, enter the following into the terminal: urescue -f -e
—It is vital that the -f and -e are there. This allows the bootloader to be over written.

10. Now we need to start the TFTP application on your PC. Open a command prompt on your PC and use the cd command to navigate to the location of your
firmware file. In my case, it is in the Downloads folder so cd c:\users\KD7VEA\Downloads puts me in the apropriate directory.

11.now we will send the file from the Computer to the Ubiquiti Device. Assuming everything has worked like it should, the Device should have the default address of 192.168.1.20
in the same command prompt that you just Changed the Directory on in step 10, Type the following.
tftp -i 192.168.1.20 put XM.v6.1.7.32555.180523.1809.bin (Substitute XM.v6.1.7.32555.180523.1809.bin for the filename for your firmware that was downloaded)

12. You should now see text being written in the terminal screen.

13. Keep watching the text until it says the device is resetting. When it does reset,
continually press any key to interrupt the boot.

14. When the boot has been interrupted, type the following in the serial console, pressing enter after each line:

mtdparts default
saveenv
boot

15. The device will now boot. Wait about 2 minutes, and then access the webpage of AirOS by
typing 192.168.1.20 in the web address bar.

16. Login to the page and navigate to the system tab. Upload the same firmware version, AirOS
v5.5.10, that you used in the urescue command.

17. Once the device reboots you will have a non-bricked device.