|Brand||Model||Version||Current Release||OEM Info||Forum Topic||Technical Data|
|AVM||FRITZ!Box 4020||19.07.4||https://avm.de/produkte/fritzbox/fritzbox-4020/||View/Edit data|
Everything is working, except for the USB port. The root hub reports having zero ports.
|Model||Version||Current Release||Firmware OpenWrt Install||Firmware OpenWrt Upgrade||Firmware OEM Stock|
OpenWrt can be installed via the EVA bootloader. The EVA bootloader waits in the first 5 seconds after power-on for an FTP connection on 192.168.178.1. Set your IP address to 192.168.178.2 and upload the image like following.
ftp -n -4 192.168.178.1 ftp> quote USER adam2 ftp> quote PASS adam2 ftp> binary ftp> debug ftp> passive ftp> quote MEDIA FLSH ftp> put openwrt-sysupgrade.bin mtd1
The process can take up to 3 minutes. After a minute, the INFO LED will illuminate Red. Once the LED turns off the process is complete and you need to powercycle to boot up OpenWrt.
AVM GPL code can be found on their FTP.
In case you are using the AVM provided recover.exe, a counter on the tffs partition will increment. It is located at 0x7AE and labeled as recovered. It currently does not seem to be incremented by the Installation methods mentioned in the next section.
To revert back to the AVM stock-firmware, you need to download the image provided on their ftp (ending in .image).
Rename the downloaded file from xyz.image to xyz.tar and extract the archive. In the /var/tmp subdirectory you find a kernel.image file. Flash it like the above described process for OpenWrt installation, use the kernel.image in the last step.
|SoC||Qualcomm QCA9561 (Dragonfly) 720MHz|
|RAM||128MB (Winbond W971GG6KB-25)|
|Flash||16 MiB SPI-NOR (Macronix MX25L12835F)|
|WiFi||Qualcomm QCA9561 3×3 b/g/n|
|Ethernet||4 x 100 Mbit/s LAN / 1 x 100 Mbit/s WAN|
|USB||1x USB 2.0|
There seem to be two different antenna layouts. One with all three antennas parallel and an other layout where two antennas are parellel and one is orthogonal. See images below:
Two antennas are parellel, one is orthogonal.
All three antennas are parallel.
Serial pinout is described here. Don't connect to 3.3V! Set to 115200N8 for connection.