Huawei Echolife HG553 is an ADSL2+ modem with WiFi router which was used by some ISP companies in Italy and Spain. The device features a Broadcom BCM6358 dual core processor clocked at 300 MHz with 64 MB RAM. The operating system is stored in a 16 MB flash memory.
The original firmware doesn't offer too many options, but there are alternate firmwares, including OpenWrt which turns this router into a highly configurable network device. If you want to use it for ADSL line, Roleo firmware (D-Link based) is the best choice. For all the other things, OpenWrt remains the best option.
Unlocking and firmware installation procedures are described in various sites. One example is OpenWrt dedicated wiki page for HG553. This post will describe the ultimate debricking procedure: writing bootloader via JTAG. After an unsuccessful firmware update and a forced restart, my router became completely unresponsive. Neither the power LED was on when powered. Reset, Failsafe mode, Telnet for this device didn't exist anymore. In this cases, there is only one solution left: JTAG.
Huawei HG553 main board