Preface
Well... I somehow soft-bricked a (luckily spare) EAP615 device after a snapshot install from April 26th so decided to try out to restore this device with serial access
Preparation
I used following documentation to verify what was needed to go through the process
-https://openwrt.org/toh/tp-link/eap615-wall
-https://openwrt.org/docs/guide-user/installation/generic.flashing.tftp
-https://openwrt.org/docs/guide-user/troubleshooting/tftpserver
-[HOWTO] Installing OpenWrt on Sophos AP 55 and AP 100
Eventually I bought following hardware
-AZDelivery CP2102 USB to TTL Converter HW-598
-Dupont Jumper cable (Male-Female) 10cm for Breadboard
-USB extension cable
And installed following software on my laptop (ubuntu)
-tftpd and tfp
Opening the EAP615-Wall was somewhat difficult but I succeeded luckily without breaking plastic parts
Procedure
- download initramfs-kernel.bin and sysupgrade.bin
- assign laptop ip 192.168.1.2 netmask 255.255.255.0
- copy initramfs-kernel.bin to /srv/tftp and test if tftp works
$ tftp 192.168.1.2
tftp> get initramfs-kernel.bin
- laptop: connect utp with PoE switch and CP2102 with EAP615
- laptop: start terminal and enter
$ sudo screen /dev/ttyUSB0 115200 - EAP615: connect utp with PoE switch to power up the device
- laptop: in serial terminal interrupt U-boot process and boot initramfs-kernel.bin
tftpboot 0x84000000 initramfs-kernel.bin
bootm
- laptop: start a new terminal and enter
$ scp -O ./openwrt-sysupgrade.bin root@192.168.1.1:/tmp
$ ssh root@192.168.1.1
root@OpenWrt:~# cd /tmp
sysupgrade openwrt-sysupgrade.bin
=> this will show few scary messages like
Cannot save config while running from ramdisk.
Fri Mar 22 22:16:12 UTC 2024 upgrade: Commencing upgrade. Closing all shell sessions.
Command failed: Connection failed
but when you look in the serial terminal you should now see the image being written, followed by a reboot