Flashing Movistar Zyxel P870HW-51Av2 with OpenWRT 14.07

Movistar Zyxel P870HW-51Av2 is a VDSL only router which isn't good for where I live but has a good CPU (BCM4350 V3.1 / 400MHz) and an acceptable amount of RAM (32MB) but with a limited flash space (4MB). However, it can get flashed with OpenWRT 14.07.

This router has CFE bootloader which makes flashing OpenWRT very easy using just a web browser. However, I wasn't able to trigger it by pressing Reset button for a few seconds during power on.

The trick to trigger CFE it is by flashing Zyxel unbranded firmware first using web admin console at http://192.168.1.1

After it finishes, flash this corrupted firmware like above to brick it and get CFE prompt afterwards.

When it get bricked you have to set a static IP for your PC (i.e: 192.168.1.2 / 255.255.255.0) and then access http://192.168.1.1

Get openwrt-P870HW-51a_v2-squashfs-cfe.bin from here and flash it. That's all

Just as a reference, I flashed the wrong firmware by accident and it became stuck in a boot loop. I had to try to unbrick it using a USB-to-TTL.

Red is GND ; Green is RX ; White is TX

This was the first time I interact with Zyxel ZLD command prompt. Unbricking was easy. just:

ATSH

ATHE

ATUR

then I sent this file via XModem (using CuteCom under GNU-Linux or TeraTerm under Windows)